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This is doc/gcj.info, produced by makeinfo version 4.12 from
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/space/rguenther/gcc-4.5.1/gcc-4.5.1/gcc/java/gcj.texi.
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Copyright (C) 2001, 2002, 2003, 2004, 2005, 2006, 2007, 2008 Free
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Software Foundation, Inc.
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7
   Permission is granted to copy, distribute and/or modify this document
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under the terms of the GNU Free Documentation License, Version 1.2 or
9
any later version published by the Free Software Foundation; with no
10
Invariant Sections, the Front-Cover Texts being (a) (see below), and
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with the Back-Cover Texts being (b) (see below).  A copy of the license
12
is included in the section entitled "GNU Free Documentation License".
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   (a) The FSF's Front-Cover Text is:
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16
   A GNU Manual
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   (b) The FSF's Back-Cover Text is:
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   You have freedom to copy and modify this GNU Manual, like GNU
21
software.  Copies published by the Free Software Foundation raise
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funds for GNU development.
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INFO-DIR-SECTION Software development
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START-INFO-DIR-ENTRY
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* Gcj: (gcj).               Ahead-of-time compiler for the Java language
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END-INFO-DIR-ENTRY
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INFO-DIR-SECTION Individual utilities
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START-INFO-DIR-ENTRY
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* jcf-dump: (gcj)Invoking jcf-dump.
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                            Print information about Java class files
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* gij: (gcj)Invoking gij.   GNU interpreter for Java bytecode
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* gcj-dbtool: (gcj)Invoking gcj-dbtool.
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                            Tool for manipulating class file databases.
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* jv-convert: (gcj)Invoking jv-convert.
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                            Convert file from one encoding to another
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* grmic: (gcj)Invoking grmic.
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                            Generate stubs for Remote Method Invocation.
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* gc-analyze: (gcj)Invoking gc-analyze.
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                            Analyze Garbage Collector (GC) memory dumps.
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* aot-compile: (gcj)Invoking aot-compile.
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                            Compile bytecode to native and generate databases.
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* rebuild-gcj-db: (gcj)Invoking rebuild-gcj-db.
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                            Merge the per-solib databases made by aot-compile
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                            into one system-wide database.
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END-INFO-DIR-ENTRY
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49
   Copyright (C) 2001, 2002, 2003, 2004, 2005, 2006, 2007, 2008 Free
50
Software Foundation, Inc.
51
 
52
   Permission is granted to copy, distribute and/or modify this document
53
under the terms of the GNU Free Documentation License, Version 1.2 or
54
any later version published by the Free Software Foundation; with no
55
Invariant Sections, the Front-Cover Texts being (a) (see below), and
56
with the Back-Cover Texts being (b) (see below).  A copy of the license
57
is included in the section entitled "GNU Free Documentation License".
58
 
59
   (a) The FSF's Front-Cover Text is:
60
 
61
   A GNU Manual
62
 
63
   (b) The FSF's Back-Cover Text is:
64
 
65
   You have freedom to copy and modify this GNU Manual, like GNU
66
software.  Copies published by the Free Software Foundation raise
67
funds for GNU development.
68
 
69

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File: gcj.info,  Node: Top,  Next: Copying,  Up: (dir)
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72
Introduction
73
************
74
 
75
This manual describes how to use `gcj', the GNU compiler for the Java
76
programming language.  `gcj' can generate both `.class' files and
77
object files, and it can read both Java source code and `.class' files.
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79
* Menu:
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81
* Copying::             The GNU General Public License
82
* GNU Free Documentation License::
83
                        How you can share and copy this manual
84
* Invoking gcj::        Compiler options supported by `gcj'
85
* Compatibility::       Compatibility between gcj and other tools for Java
86
* Invoking jcf-dump::   Print information about class files
87
* Invoking gij::        Interpreting Java bytecodes
88
* Invoking gcj-dbtool:: Tool for manipulating class file databases.
89
* Invoking jv-convert:: Converting from one encoding to another
90
* Invoking grmic::      Generate stubs for Remote Method Invocation.
91
* Invoking gc-analyze:: Analyze Garbage Collector (GC) memory dumps.
92
* Invoking aot-compile:: Compile bytecode to native and generate databases.
93
* Invoking rebuild-gcj-db:: Merge the per-solib databases made by aot-compile
94
                            into one system-wide database.
95
* About CNI::           Description of the Compiled Native Interface
96
* System properties::   Modifying runtime behavior of the libgcj library
97
* Resources::           Where to look for more information
98
* Index::               Index.
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File: gcj.info,  Node: Copying,  Next: GNU Free Documentation License,  Prev: Top,  Up: Top
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103
GNU General Public License
104
**************************
105
 
106
                        Version 3, 29 June 2007
107
 
108
     Copyright (C) 2007 Free Software Foundation, Inc. `http://fsf.org/'
109
 
110
     Everyone is permitted to copy and distribute verbatim copies of this
111
     license document, but changing it is not allowed.
112
 
113
Preamble
114
========
115
 
116
The GNU General Public License is a free, copyleft license for software
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and other kinds of works.
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119
   The licenses for most software and other practical works are designed
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to take away your freedom to share and change the works.  By contrast,
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the GNU General Public License is intended to guarantee your freedom to
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GNU General Public License for most of our software; it applies also to
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any other work released this way by its authors.  You can apply it to
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   When we speak of free software, we are referring to freedom, not
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   The precise terms and conditions for copying, distribution and
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TERMS AND CONDITIONS
179
====================
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  8. Termination.
536
 
537
     You may not propagate or modify a covered work except as expressly
538
     provided under this License.  Any attempt otherwise to propagate or
539
     modify it is void, and will automatically terminate your rights
540
     under this License (including any patent licenses granted under
541
     the third paragraph of section 11).
542
 
543
     However, if you cease all violation of this License, then your
544
     license from a particular copyright holder is reinstated (a)
545
     provisionally, unless and until the copyright holder explicitly
546
     and finally terminates your license, and (b) permanently, if the
547
     copyright holder fails to notify you of the violation by some
548
     reasonable means prior to 60 days after the cessation.
549
 
550
     Moreover, your license from a particular copyright holder is
551
     reinstated permanently if the copyright holder notifies you of the
552
     violation by some reasonable means, this is the first time you have
553
     received notice of violation of this License (for any work) from
554
     that copyright holder, and you cure the violation prior to 30 days
555
     after your receipt of the notice.
556
 
557
     Termination of your rights under this section does not terminate
558
     the licenses of parties who have received copies or rights from
559
     you under this License.  If your rights have been terminated and
560
     not permanently reinstated, you do not qualify to receive new
561
     licenses for the same material under section 10.
562
 
563
  9. Acceptance Not Required for Having Copies.
564
 
565
     You are not required to accept this License in order to receive or
566
     run a copy of the Program.  Ancillary propagation of a covered work
567
     occurring solely as a consequence of using peer-to-peer
568
     transmission to receive a copy likewise does not require
569
     acceptance.  However, nothing other than this License grants you
570
     permission to propagate or modify any covered work.  These actions
571
     infringe copyright if you do not accept this License.  Therefore,
572
     by modifying or propagating a covered work, you indicate your
573
     acceptance of this License to do so.
574
 
575
 10. Automatic Licensing of Downstream Recipients.
576
 
577
     Each time you convey a covered work, the recipient automatically
578
     receives a license from the original licensors, to run, modify and
579
     propagate that work, subject to this License.  You are not
580
     responsible for enforcing compliance by third parties with this
581
     License.
582
 
583
     An "entity transaction" is a transaction transferring control of an
584
     organization, or substantially all assets of one, or subdividing an
585
     organization, or merging organizations.  If propagation of a
586
     covered work results from an entity transaction, each party to that
587
     transaction who receives a copy of the work also receives whatever
588
     licenses to the work the party's predecessor in interest had or
589
     could give under the previous paragraph, plus a right to
590
     possession of the Corresponding Source of the work from the
591
     predecessor in interest, if the predecessor has it or can get it
592
     with reasonable efforts.
593
 
594
     You may not impose any further restrictions on the exercise of the
595
     rights granted or affirmed under this License.  For example, you
596
     may not impose a license fee, royalty, or other charge for
597
     exercise of rights granted under this License, and you may not
598
     initiate litigation (including a cross-claim or counterclaim in a
599
     lawsuit) alleging that any patent claim is infringed by making,
600
     using, selling, offering for sale, or importing the Program or any
601
     portion of it.
602
 
603
 11. Patents.
604
 
605
     A "contributor" is a copyright holder who authorizes use under this
606
     License of the Program or a work on which the Program is based.
607
     The work thus licensed is called the contributor's "contributor
608
     version".
609
 
610
     A contributor's "essential patent claims" are all patent claims
611
     owned or controlled by the contributor, whether already acquired or
612
     hereafter acquired, that would be infringed by some manner,
613
     permitted by this License, of making, using, or selling its
614
     contributor version, but do not include claims that would be
615
     infringed only as a consequence of further modification of the
616
     contributor version.  For purposes of this definition, "control"
617
     includes the right to grant patent sublicenses in a manner
618
     consistent with the requirements of this License.
619
 
620
     Each contributor grants you a non-exclusive, worldwide,
621
     royalty-free patent license under the contributor's essential
622
     patent claims, to make, use, sell, offer for sale, import and
623
     otherwise run, modify and propagate the contents of its
624
     contributor version.
625
 
626
     In the following three paragraphs, a "patent license" is any
627
     express agreement or commitment, however denominated, not to
628
     enforce a patent (such as an express permission to practice a
629
     patent or covenant not to sue for patent infringement).  To
630
     "grant" such a patent license to a party means to make such an
631
     agreement or commitment not to enforce a patent against the party.
632
 
633
     If you convey a covered work, knowingly relying on a patent
634
     license, and the Corresponding Source of the work is not available
635
     for anyone to copy, free of charge and under the terms of this
636
     License, through a publicly available network server or other
637
     readily accessible means, then you must either (1) cause the
638
     Corresponding Source to be so available, or (2) arrange to deprive
639
     yourself of the benefit of the patent license for this particular
640
     work, or (3) arrange, in a manner consistent with the requirements
641
     of this License, to extend the patent license to downstream
642
     recipients.  "Knowingly relying" means you have actual knowledge
643
     that, but for the patent license, your conveying the covered work
644
     in a country, or your recipient's use of the covered work in a
645
     country, would infringe one or more identifiable patents in that
646
     country that you have reason to believe are valid.
647
 
648
     If, pursuant to or in connection with a single transaction or
649
     arrangement, you convey, or propagate by procuring conveyance of, a
650
     covered work, and grant a patent license to some of the parties
651
     receiving the covered work authorizing them to use, propagate,
652
     modify or convey a specific copy of the covered work, then the
653
     patent license you grant is automatically extended to all
654
     recipients of the covered work and works based on it.
655
 
656
     A patent license is "discriminatory" if it does not include within
657
     the scope of its coverage, prohibits the exercise of, or is
658
     conditioned on the non-exercise of one or more of the rights that
659
     are specifically granted under this License.  You may not convey a
660
     covered work if you are a party to an arrangement with a third
661
     party that is in the business of distributing software, under
662
     which you make payment to the third party based on the extent of
663
     your activity of conveying the work, and under which the third
664
     party grants, to any of the parties who would receive the covered
665
     work from you, a discriminatory patent license (a) in connection
666
     with copies of the covered work conveyed by you (or copies made
667
     from those copies), or (b) primarily for and in connection with
668
     specific products or compilations that contain the covered work,
669
     unless you entered into that arrangement, or that patent license
670
     was granted, prior to 28 March 2007.
671
 
672
     Nothing in this License shall be construed as excluding or limiting
673
     any implied license or other defenses to infringement that may
674
     otherwise be available to you under applicable patent law.
675
 
676
 12. No Surrender of Others' Freedom.
677
 
678
     If conditions are imposed on you (whether by court order,
679
     agreement or otherwise) that contradict the conditions of this
680
     License, they do not excuse you from the conditions of this
681
     License.  If you cannot convey a covered work so as to satisfy
682
     simultaneously your obligations under this License and any other
683
     pertinent obligations, then as a consequence you may not convey it
684
     at all.  For example, if you agree to terms that obligate you to
685
     collect a royalty for further conveying from those to whom you
686
     convey the Program, the only way you could satisfy both those
687
     terms and this License would be to refrain entirely from conveying
688
     the Program.
689
 
690
 13. Use with the GNU Affero General Public License.
691
 
692
     Notwithstanding any other provision of this License, you have
693
     permission to link or combine any covered work with a work licensed
694
     under version 3 of the GNU Affero General Public License into a
695
     single combined work, and to convey the resulting work.  The terms
696
     of this License will continue to apply to the part which is the
697
     covered work, but the special requirements of the GNU Affero
698
     General Public License, section 13, concerning interaction through
699
     a network will apply to the combination as such.
700
 
701
 14. Revised Versions of this License.
702
 
703
     The Free Software Foundation may publish revised and/or new
704
     versions of the GNU General Public License from time to time.
705
     Such new versions will be similar in spirit to the present
706
     version, but may differ in detail to address new problems or
707
     concerns.
708
 
709
     Each version is given a distinguishing version number.  If the
710
     Program specifies that a certain numbered version of the GNU
711
     General Public License "or any later version" applies to it, you
712
     have the option of following the terms and conditions either of
713
     that numbered version or of any later version published by the
714
     Free Software Foundation.  If the Program does not specify a
715
     version number of the GNU General Public License, you may choose
716
     any version ever published by the Free Software Foundation.
717
 
718
     If the Program specifies that a proxy can decide which future
719
     versions of the GNU General Public License can be used, that
720
     proxy's public statement of acceptance of a version permanently
721
     authorizes you to choose that version for the Program.
722
 
723
     Later license versions may give you additional or different
724
     permissions.  However, no additional obligations are imposed on any
725
     author or copyright holder as a result of your choosing to follow a
726
     later version.
727
 
728
 15. Disclaimer of Warranty.
729
 
730
     THERE IS NO WARRANTY FOR THE PROGRAM, TO THE EXTENT PERMITTED BY
731
     APPLICABLE LAW.  EXCEPT WHEN OTHERWISE STATED IN WRITING THE
732
     COPYRIGHT HOLDERS AND/OR OTHER PARTIES PROVIDE THE PROGRAM "AS IS"
733
     WITHOUT WARRANTY OF ANY KIND, EITHER EXPRESSED OR IMPLIED,
734
     INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
735
     MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE.  THE ENTIRE
736
     RISK AS TO THE QUALITY AND PERFORMANCE OF THE PROGRAM IS WITH YOU.
737
     SHOULD THE PROGRAM PROVE DEFECTIVE, YOU ASSUME THE COST OF ALL
738
     NECESSARY SERVICING, REPAIR OR CORRECTION.
739
 
740
 16. Limitation of Liability.
741
 
742
     IN NO EVENT UNLESS REQUIRED BY APPLICABLE LAW OR AGREED TO IN
743
     WRITING WILL ANY COPYRIGHT HOLDER, OR ANY OTHER PARTY WHO MODIFIES
744
     AND/OR CONVEYS THE PROGRAM AS PERMITTED ABOVE, BE LIABLE TO YOU
745
     FOR DAMAGES, INCLUDING ANY GENERAL, SPECIAL, INCIDENTAL OR
746
     CONSEQUENTIAL DAMAGES ARISING OUT OF THE USE OR INABILITY TO USE
747
     THE PROGRAM (INCLUDING BUT NOT LIMITED TO LOSS OF DATA OR DATA
748
     BEING RENDERED INACCURATE OR LOSSES SUSTAINED BY YOU OR THIRD
749
     PARTIES OR A FAILURE OF THE PROGRAM TO OPERATE WITH ANY OTHER
750
     PROGRAMS), EVEN IF SUCH HOLDER OR OTHER PARTY HAS BEEN ADVISED OF
751
     THE POSSIBILITY OF SUCH DAMAGES.
752
 
753
 17. Interpretation of Sections 15 and 16.
754
 
755
     If the disclaimer of warranty and limitation of liability provided
756
     above cannot be given local legal effect according to their terms,
757
     reviewing courts shall apply local law that most closely
758
     approximates an absolute waiver of all civil liability in
759
     connection with the Program, unless a warranty or assumption of
760
     liability accompanies a copy of the Program in return for a fee.
761
 
762
 
763
END OF TERMS AND CONDITIONS
764
===========================
765
 
766
How to Apply These Terms to Your New Programs
767
=============================================
768
 
769
If you develop a new program, and you want it to be of the greatest
770
possible use to the public, the best way to achieve this is to make it
771
free software which everyone can redistribute and change under these
772
terms.
773
 
774
   To do so, attach the following notices to the program.  It is safest
775
to attach them to the start of each source file to most effectively
776
state the exclusion of warranty; and each file should have at least the
777
"copyright" line and a pointer to where the full notice is found.
778
 
779
     ONE LINE TO GIVE THE PROGRAM'S NAME AND A BRIEF IDEA OF WHAT IT DOES.
780
     Copyright (C) YEAR NAME OF AUTHOR
781
 
782
     This program is free software: you can redistribute it and/or modify
783
     it under the terms of the GNU General Public License as published by
784
     the Free Software Foundation, either version 3 of the License, or (at
785
     your option) any later version.
786
 
787
     This program is distributed in the hope that it will be useful, but
788
     WITHOUT ANY WARRANTY; without even the implied warranty of
789
     MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
790
     General Public License for more details.
791
 
792
     You should have received a copy of the GNU General Public License
793
     along with this program.  If not, see `http://www.gnu.org/licenses/'.
794
 
795
   Also add information on how to contact you by electronic and paper
796
mail.
797
 
798
   If the program does terminal interaction, make it output a short
799
notice like this when it starts in an interactive mode:
800
 
801
     PROGRAM Copyright (C) YEAR NAME OF AUTHOR
802
     This program comes with ABSOLUTELY NO WARRANTY; for details type `show w'.
803
     This is free software, and you are welcome to redistribute it
804
     under certain conditions; type `show c' for details.
805
 
806
   The hypothetical commands `show w' and `show c' should show the
807
appropriate parts of the General Public License.  Of course, your
808
program's commands might be different; for a GUI interface, you would
809
use an "about box".
810
 
811
   You should also get your employer (if you work as a programmer) or
812
school, if any, to sign a "copyright disclaimer" for the program, if
813
necessary.  For more information on this, and how to apply and follow
814
the GNU GPL, see `http://www.gnu.org/licenses/'.
815
 
816
   The GNU General Public License does not permit incorporating your
817
program into proprietary programs.  If your program is a subroutine
818
library, you may consider it more useful to permit linking proprietary
819
applications with the library.  If this is what you want to do, use the
820
GNU Lesser General Public License instead of this License.  But first,
821
please read `http://www.gnu.org/philosophy/why-not-lgpl.html'.
822
 
823

824
File: gcj.info,  Node: GNU Free Documentation License,  Next: Invoking gcj,  Prev: Copying,  Up: Top
825
 
826
GNU Free Documentation License
827
******************************
828
 
829
                      Version 1.2, November 2002
830
 
831
     Copyright (C) 2000,2001,2002 Free Software Foundation, Inc.
832
     51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA
833
 
834
     Everyone is permitted to copy and distribute verbatim copies
835
     of this license document, but changing it is not allowed.
836
 
837
  0. PREAMBLE
838
 
839
     The purpose of this License is to make a manual, textbook, or other
840
     functional and useful document "free" in the sense of freedom: to
841
     assure everyone the effective freedom to copy and redistribute it,
842
     with or without modifying it, either commercially or
843
     noncommercially.  Secondarily, this License preserves for the
844
     author and publisher a way to get credit for their work, while not
845
     being considered responsible for modifications made by others.
846
 
847
     This License is a kind of "copyleft", which means that derivative
848
     works of the document must themselves be free in the same sense.
849
     It complements the GNU General Public License, which is a copyleft
850
     license designed for free software.
851
 
852
     We have designed this License in order to use it for manuals for
853
     free software, because free software needs free documentation: a
854
     free program should come with manuals providing the same freedoms
855
     that the software does.  But this License is not limited to
856
     software manuals; it can be used for any textual work, regardless
857
     of subject matter or whether it is published as a printed book.
858
     We recommend this License principally for works whose purpose is
859
     instruction or reference.
860
 
861
  1. APPLICABILITY AND DEFINITIONS
862
 
863
     This License applies to any manual or other work, in any medium,
864
     that contains a notice placed by the copyright holder saying it
865
     can be distributed under the terms of this License.  Such a notice
866
     grants a world-wide, royalty-free license, unlimited in duration,
867
     to use that work under the conditions stated herein.  The
868
     "Document", below, refers to any such manual or work.  Any member
869
     of the public is a licensee, and is addressed as "you".  You
870
     accept the license if you copy, modify or distribute the work in a
871
     way requiring permission under copyright law.
872
 
873
     A "Modified Version" of the Document means any work containing the
874
     Document or a portion of it, either copied verbatim, or with
875
     modifications and/or translated into another language.
876
 
877
     A "Secondary Section" is a named appendix or a front-matter section
878
     of the Document that deals exclusively with the relationship of the
879
     publishers or authors of the Document to the Document's overall
880
     subject (or to related matters) and contains nothing that could
881
     fall directly within that overall subject.  (Thus, if the Document
882
     is in part a textbook of mathematics, a Secondary Section may not
883
     explain any mathematics.)  The relationship could be a matter of
884
     historical connection with the subject or with related matters, or
885
     of legal, commercial, philosophical, ethical or political position
886
     regarding them.
887
 
888
     The "Invariant Sections" are certain Secondary Sections whose
889
     titles are designated, as being those of Invariant Sections, in
890
     the notice that says that the Document is released under this
891
     License.  If a section does not fit the above definition of
892
     Secondary then it is not allowed to be designated as Invariant.
893
     The Document may contain zero Invariant Sections.  If the Document
894
     does not identify any Invariant Sections then there are none.
895
 
896
     The "Cover Texts" are certain short passages of text that are
897
     listed, as Front-Cover Texts or Back-Cover Texts, in the notice
898
     that says that the Document is released under this License.  A
899
     Front-Cover Text may be at most 5 words, and a Back-Cover Text may
900
     be at most 25 words.
901
 
902
     A "Transparent" copy of the Document means a machine-readable copy,
903
     represented in a format whose specification is available to the
904
     general public, that is suitable for revising the document
905
     straightforwardly with generic text editors or (for images
906
     composed of pixels) generic paint programs or (for drawings) some
907
     widely available drawing editor, and that is suitable for input to
908
     text formatters or for automatic translation to a variety of
909
     formats suitable for input to text formatters.  A copy made in an
910
     otherwise Transparent file format whose markup, or absence of
911
     markup, has been arranged to thwart or discourage subsequent
912
     modification by readers is not Transparent.  An image format is
913
     not Transparent if used for any substantial amount of text.  A
914
     copy that is not "Transparent" is called "Opaque".
915
 
916
     Examples of suitable formats for Transparent copies include plain
917
     ASCII without markup, Texinfo input format, LaTeX input format,
918
     SGML or XML using a publicly available DTD, and
919
     standard-conforming simple HTML, PostScript or PDF designed for
920
     human modification.  Examples of transparent image formats include
921
     PNG, XCF and JPG.  Opaque formats include proprietary formats that
922
     can be read and edited only by proprietary word processors, SGML or
923
     XML for which the DTD and/or processing tools are not generally
924
     available, and the machine-generated HTML, PostScript or PDF
925
     produced by some word processors for output purposes only.
926
 
927
     The "Title Page" means, for a printed book, the title page itself,
928
     plus such following pages as are needed to hold, legibly, the
929
     material this License requires to appear in the title page.  For
930
     works in formats which do not have any title page as such, "Title
931
     Page" means the text near the most prominent appearance of the
932
     work's title, preceding the beginning of the body of the text.
933
 
934
     A section "Entitled XYZ" means a named subunit of the Document
935
     whose title either is precisely XYZ or contains XYZ in parentheses
936
     following text that translates XYZ in another language.  (Here XYZ
937
     stands for a specific section name mentioned below, such as
938
     "Acknowledgements", "Dedications", "Endorsements", or "History".)
939
     To "Preserve the Title" of such a section when you modify the
940
     Document means that it remains a section "Entitled XYZ" according
941
     to this definition.
942
 
943
     The Document may include Warranty Disclaimers next to the notice
944
     which states that this License applies to the Document.  These
945
     Warranty Disclaimers are considered to be included by reference in
946
     this License, but only as regards disclaiming warranties: any other
947
     implication that these Warranty Disclaimers may have is void and
948
     has no effect on the meaning of this License.
949
 
950
  2. VERBATIM COPYING
951
 
952
     You may copy and distribute the Document in any medium, either
953
     commercially or noncommercially, provided that this License, the
954
     copyright notices, and the license notice saying this License
955
     applies to the Document are reproduced in all copies, and that you
956
     add no other conditions whatsoever to those of this License.  You
957
     may not use technical measures to obstruct or control the reading
958
     or further copying of the copies you make or distribute.  However,
959
     you may accept compensation in exchange for copies.  If you
960
     distribute a large enough number of copies you must also follow
961
     the conditions in section 3.
962
 
963
     You may also lend copies, under the same conditions stated above,
964
     and you may publicly display copies.
965
 
966
  3. COPYING IN QUANTITY
967
 
968
     If you publish printed copies (or copies in media that commonly
969
     have printed covers) of the Document, numbering more than 100, and
970
     the Document's license notice requires Cover Texts, you must
971
     enclose the copies in covers that carry, clearly and legibly, all
972
     these Cover Texts: Front-Cover Texts on the front cover, and
973
     Back-Cover Texts on the back cover.  Both covers must also clearly
974
     and legibly identify you as the publisher of these copies.  The
975
     front cover must present the full title with all words of the
976
     title equally prominent and visible.  You may add other material
977
     on the covers in addition.  Copying with changes limited to the
978
     covers, as long as they preserve the title of the Document and
979
     satisfy these conditions, can be treated as verbatim copying in
980
     other respects.
981
 
982
     If the required texts for either cover are too voluminous to fit
983
     legibly, you should put the first ones listed (as many as fit
984
     reasonably) on the actual cover, and continue the rest onto
985
     adjacent pages.
986
 
987
     If you publish or distribute Opaque copies of the Document
988
     numbering more than 100, you must either include a
989
     machine-readable Transparent copy along with each Opaque copy, or
990
     state in or with each Opaque copy a computer-network location from
991
     which the general network-using public has access to download
992
     using public-standard network protocols a complete Transparent
993
     copy of the Document, free of added material.  If you use the
994
     latter option, you must take reasonably prudent steps, when you
995
     begin distribution of Opaque copies in quantity, to ensure that
996
     this Transparent copy will remain thus accessible at the stated
997
     location until at least one year after the last time you
998
     distribute an Opaque copy (directly or through your agents or
999
     retailers) of that edition to the public.
1000
 
1001
     It is requested, but not required, that you contact the authors of
1002
     the Document well before redistributing any large number of
1003
     copies, to give them a chance to provide you with an updated
1004
     version of the Document.
1005
 
1006
  4. MODIFICATIONS
1007
 
1008
     You may copy and distribute a Modified Version of the Document
1009
     under the conditions of sections 2 and 3 above, provided that you
1010
     release the Modified Version under precisely this License, with
1011
     the Modified Version filling the role of the Document, thus
1012
     licensing distribution and modification of the Modified Version to
1013
     whoever possesses a copy of it.  In addition, you must do these
1014
     things in the Modified Version:
1015
 
1016
       A. Use in the Title Page (and on the covers, if any) a title
1017
          distinct from that of the Document, and from those of
1018
          previous versions (which should, if there were any, be listed
1019
          in the History section of the Document).  You may use the
1020
          same title as a previous version if the original publisher of
1021
          that version gives permission.
1022
 
1023
       B. List on the Title Page, as authors, one or more persons or
1024
          entities responsible for authorship of the modifications in
1025
          the Modified Version, together with at least five of the
1026
          principal authors of the Document (all of its principal
1027
          authors, if it has fewer than five), unless they release you
1028
          from this requirement.
1029
 
1030
       C. State on the Title page the name of the publisher of the
1031
          Modified Version, as the publisher.
1032
 
1033
       D. Preserve all the copyright notices of the Document.
1034
 
1035
       E. Add an appropriate copyright notice for your modifications
1036
          adjacent to the other copyright notices.
1037
 
1038
       F. Include, immediately after the copyright notices, a license
1039
          notice giving the public permission to use the Modified
1040
          Version under the terms of this License, in the form shown in
1041
          the Addendum below.
1042
 
1043
       G. Preserve in that license notice the full lists of Invariant
1044
          Sections and required Cover Texts given in the Document's
1045
          license notice.
1046
 
1047
       H. Include an unaltered copy of this License.
1048
 
1049
       I. Preserve the section Entitled "History", Preserve its Title,
1050
          and add to it an item stating at least the title, year, new
1051
          authors, and publisher of the Modified Version as given on
1052
          the Title Page.  If there is no section Entitled "History" in
1053
          the Document, create one stating the title, year, authors,
1054
          and publisher of the Document as given on its Title Page,
1055
          then add an item describing the Modified Version as stated in
1056
          the previous sentence.
1057
 
1058
       J. Preserve the network location, if any, given in the Document
1059
          for public access to a Transparent copy of the Document, and
1060
          likewise the network locations given in the Document for
1061
          previous versions it was based on.  These may be placed in
1062
          the "History" section.  You may omit a network location for a
1063
          work that was published at least four years before the
1064
          Document itself, or if the original publisher of the version
1065
          it refers to gives permission.
1066
 
1067
       K. For any section Entitled "Acknowledgements" or "Dedications",
1068
          Preserve the Title of the section, and preserve in the
1069
          section all the substance and tone of each of the contributor
1070
          acknowledgements and/or dedications given therein.
1071
 
1072
       L. Preserve all the Invariant Sections of the Document,
1073
          unaltered in their text and in their titles.  Section numbers
1074
          or the equivalent are not considered part of the section
1075
          titles.
1076
 
1077
       M. Delete any section Entitled "Endorsements".  Such a section
1078
          may not be included in the Modified Version.
1079
 
1080
       N. Do not retitle any existing section to be Entitled
1081
          "Endorsements" or to conflict in title with any Invariant
1082
          Section.
1083
 
1084
       O. Preserve any Warranty Disclaimers.
1085
 
1086
     If the Modified Version includes new front-matter sections or
1087
     appendices that qualify as Secondary Sections and contain no
1088
     material copied from the Document, you may at your option
1089
     designate some or all of these sections as invariant.  To do this,
1090
     add their titles to the list of Invariant Sections in the Modified
1091
     Version's license notice.  These titles must be distinct from any
1092
     other section titles.
1093
 
1094
     You may add a section Entitled "Endorsements", provided it contains
1095
     nothing but endorsements of your Modified Version by various
1096
     parties--for example, statements of peer review or that the text
1097
     has been approved by an organization as the authoritative
1098
     definition of a standard.
1099
 
1100
     You may add a passage of up to five words as a Front-Cover Text,
1101
     and a passage of up to 25 words as a Back-Cover Text, to the end
1102
     of the list of Cover Texts in the Modified Version.  Only one
1103
     passage of Front-Cover Text and one of Back-Cover Text may be
1104
     added by (or through arrangements made by) any one entity.  If the
1105
     Document already includes a cover text for the same cover,
1106
     previously added by you or by arrangement made by the same entity
1107
     you are acting on behalf of, you may not add another; but you may
1108
     replace the old one, on explicit permission from the previous
1109
     publisher that added the old one.
1110
 
1111
     The author(s) and publisher(s) of the Document do not by this
1112
     License give permission to use their names for publicity for or to
1113
     assert or imply endorsement of any Modified Version.
1114
 
1115
  5. COMBINING DOCUMENTS
1116
 
1117
     You may combine the Document with other documents released under
1118
     this License, under the terms defined in section 4 above for
1119
     modified versions, provided that you include in the combination
1120
     all of the Invariant Sections of all of the original documents,
1121
     unmodified, and list them all as Invariant Sections of your
1122
     combined work in its license notice, and that you preserve all
1123
     their Warranty Disclaimers.
1124
 
1125
     The combined work need only contain one copy of this License, and
1126
     multiple identical Invariant Sections may be replaced with a single
1127
     copy.  If there are multiple Invariant Sections with the same name
1128
     but different contents, make the title of each such section unique
1129
     by adding at the end of it, in parentheses, the name of the
1130
     original author or publisher of that section if known, or else a
1131
     unique number.  Make the same adjustment to the section titles in
1132
     the list of Invariant Sections in the license notice of the
1133
     combined work.
1134
 
1135
     In the combination, you must combine any sections Entitled
1136
     "History" in the various original documents, forming one section
1137
     Entitled "History"; likewise combine any sections Entitled
1138
     "Acknowledgements", and any sections Entitled "Dedications".  You
1139
     must delete all sections Entitled "Endorsements."
1140
 
1141
  6. COLLECTIONS OF DOCUMENTS
1142
 
1143
     You may make a collection consisting of the Document and other
1144
     documents released under this License, and replace the individual
1145
     copies of this License in the various documents with a single copy
1146
     that is included in the collection, provided that you follow the
1147
     rules of this License for verbatim copying of each of the
1148
     documents in all other respects.
1149
 
1150
     You may extract a single document from such a collection, and
1151
     distribute it individually under this License, provided you insert
1152
     a copy of this License into the extracted document, and follow
1153
     this License in all other respects regarding verbatim copying of
1154
     that document.
1155
 
1156
  7. AGGREGATION WITH INDEPENDENT WORKS
1157
 
1158
     A compilation of the Document or its derivatives with other
1159
     separate and independent documents or works, in or on a volume of
1160
     a storage or distribution medium, is called an "aggregate" if the
1161
     copyright resulting from the compilation is not used to limit the
1162
     legal rights of the compilation's users beyond what the individual
1163
     works permit.  When the Document is included in an aggregate, this
1164
     License does not apply to the other works in the aggregate which
1165
     are not themselves derivative works of the Document.
1166
 
1167
     If the Cover Text requirement of section 3 is applicable to these
1168
     copies of the Document, then if the Document is less than one half
1169
     of the entire aggregate, the Document's Cover Texts may be placed
1170
     on covers that bracket the Document within the aggregate, or the
1171
     electronic equivalent of covers if the Document is in electronic
1172
     form.  Otherwise they must appear on printed covers that bracket
1173
     the whole aggregate.
1174
 
1175
  8. TRANSLATION
1176
 
1177
     Translation is considered a kind of modification, so you may
1178
     distribute translations of the Document under the terms of section
1179
     4.  Replacing Invariant Sections with translations requires special
1180
     permission from their copyright holders, but you may include
1181
     translations of some or all Invariant Sections in addition to the
1182
     original versions of these Invariant Sections.  You may include a
1183
     translation of this License, and all the license notices in the
1184
     Document, and any Warranty Disclaimers, provided that you also
1185
     include the original English version of this License and the
1186
     original versions of those notices and disclaimers.  In case of a
1187
     disagreement between the translation and the original version of
1188
     this License or a notice or disclaimer, the original version will
1189
     prevail.
1190
 
1191
     If a section in the Document is Entitled "Acknowledgements",
1192
     "Dedications", or "History", the requirement (section 4) to
1193
     Preserve its Title (section 1) will typically require changing the
1194
     actual title.
1195
 
1196
  9. TERMINATION
1197
 
1198
     You may not copy, modify, sublicense, or distribute the Document
1199
     except as expressly provided for under this License.  Any other
1200
     attempt to copy, modify, sublicense or distribute the Document is
1201
     void, and will automatically terminate your rights under this
1202
     License.  However, parties who have received copies, or rights,
1203
     from you under this License will not have their licenses
1204
     terminated so long as such parties remain in full compliance.
1205
 
1206
 10. FUTURE REVISIONS OF THIS LICENSE
1207
 
1208
     The Free Software Foundation may publish new, revised versions of
1209
     the GNU Free Documentation License from time to time.  Such new
1210
     versions will be similar in spirit to the present version, but may
1211
     differ in detail to address new problems or concerns.  See
1212
     `http://www.gnu.org/copyleft/'.
1213
 
1214
     Each version of the License is given a distinguishing version
1215
     number.  If the Document specifies that a particular numbered
1216
     version of this License "or any later version" applies to it, you
1217
     have the option of following the terms and conditions either of
1218
     that specified version or of any later version that has been
1219
     published (not as a draft) by the Free Software Foundation.  If
1220
     the Document does not specify a version number of this License,
1221
     you may choose any version ever published (not as a draft) by the
1222
     Free Software Foundation.
1223
 
1224
ADDENDUM: How to use this License for your documents
1225
====================================================
1226
 
1227
To use this License in a document you have written, include a copy of
1228
the License in the document and put the following copyright and license
1229
notices just after the title page:
1230
 
1231
       Copyright (C)  YEAR  YOUR NAME.
1232
       Permission is granted to copy, distribute and/or modify this document
1233
       under the terms of the GNU Free Documentation License, Version 1.2
1234
       or any later version published by the Free Software Foundation;
1235
       with no Invariant Sections, no Front-Cover Texts, and no Back-Cover
1236
       Texts.  A copy of the license is included in the section entitled ``GNU
1237
       Free Documentation License''.
1238
 
1239
   If you have Invariant Sections, Front-Cover Texts and Back-Cover
1240
Texts, replace the "with...Texts." line with this:
1241
 
1242
         with the Invariant Sections being LIST THEIR TITLES, with
1243
         the Front-Cover Texts being LIST, and with the Back-Cover Texts
1244
         being LIST.
1245
 
1246
   If you have Invariant Sections without Cover Texts, or some other
1247
combination of the three, merge those two alternatives to suit the
1248
situation.
1249
 
1250
   If your document contains nontrivial examples of program code, we
1251
recommend releasing these examples in parallel under your choice of
1252
free software license, such as the GNU General Public License, to
1253
permit their use in free software.
1254
 
1255

1256
File: gcj.info,  Node: Invoking gcj,  Next: Compatibility,  Prev: GNU Free Documentation License,  Up: Top
1257
 
1258
1 Invoking gcj
1259
**************
1260
 
1261
As `gcj' is just another front end to `gcc', it supports many of the
1262
same options as gcc.  *Note Option Summary: (gcc)Option Summary.  This
1263
manual only documents the options specific to `gcj'.
1264
 
1265
* Menu:
1266
 
1267
* Input and output files::
1268
* Input Options::               How gcj finds files
1269
* Encodings::                   Options controlling source file encoding
1270
* Warnings::                    Options controlling warnings specific to gcj
1271
* Linking::                     Options for making an executable
1272
* Code Generation::             Options controlling the output of gcj
1273
* Configure-time Options::      Options you won't use
1274
 
1275

1276
File: gcj.info,  Node: Input and output files,  Next: Input Options,  Up: Invoking gcj
1277
 
1278
1.1 Input and output files
1279
==========================
1280
 
1281
A `gcj' command is like a `gcc' command, in that it consists of a
1282
number of options and file names.  The following kinds of input file
1283
names are supported:
1284
 
1285
`FILE.java'
1286
     Java source files.
1287
 
1288
`FILE.class'
1289
     Java bytecode files.
1290
 
1291
`FILE.zip'
1292
`FILE.jar'
1293
     An archive containing one or more `.class' files, all of which are
1294
     compiled.  The archive may be compressed.  Files in an archive
1295
     which don't end with `.class' are treated as resource files; they
1296
     are compiled into the resulting object file as `core:' URLs.
1297
 
1298
`@FILE'
1299
     A file containing a whitespace-separated list of input file names.
1300
     (Currently, these must all be `.java' source files, but that may
1301
     change.)  Each named file is compiled, just as if it had been on
1302
     the command line.
1303
 
1304
`LIBRARY.a'
1305
`LIBRARY.so'
1306
`-lLIBNAME'
1307
     Libraries to use when linking.  See the `gcc' manual.
1308
 
1309
   You can specify more than one input file on the `gcj' command line,
1310
in which case they will all be compiled.  If you specify a `-o FILENAME'
1311
option, all the input files will be compiled together, producing a
1312
single output file, named FILENAME.  This is allowed even when using
1313
`-S' or `-c', but not when using `-C' or `--resource'.  (This is an
1314
extension beyond the what plain `gcc' allows.)  (If more than one input
1315
file is specified, all must currently be `.java' files, though we hope
1316
to fix this.)
1317
 
1318

1319
File: gcj.info,  Node: Input Options,  Next: Encodings,  Prev: Input and output files,  Up: Invoking gcj
1320
 
1321
1.2 Input Options
1322
=================
1323
 
1324
`gcj' has options to control where it looks to find files it needs.
1325
For instance, `gcj' might need to load a class that is referenced by
1326
the file it has been asked to compile.  Like other compilers for the
1327
Java language, `gcj' has a notion of a "class path".  There are several
1328
options and environment variables which can be used to manipulate the
1329
class path.  When `gcj' looks for a given class, it searches the class
1330
path looking for matching `.class' or `.java' file.  `gcj' comes with a
1331
built-in class path which points at the installed `libgcj.jar', a file
1332
which contains all the standard classes.
1333
 
1334
   In the text below, a directory or path component can refer either to
1335
an actual directory on the filesystem, or to a `.zip' or `.jar' file,
1336
which `gcj' will search as if it is a directory.
1337
 
1338
`-IDIR'
1339
     All directories specified by `-I' are kept in order and prepended
1340
     to the class path constructed from all the other options.  Unless
1341
     compatibility with tools like `javac' is important, we recommend
1342
     always using `-I' instead of the other options for manipulating the
1343
     class path.
1344
 
1345
`--classpath=PATH'
1346
     This sets the class path to PATH, a colon-separated list of paths
1347
     (on Windows-based systems, a semicolon-separate list of paths).
1348
     This does not override the builtin ("boot") search path.
1349
 
1350
`--CLASSPATH=PATH'
1351
     Deprecated synonym for `--classpath'.
1352
 
1353
`--bootclasspath=PATH'
1354
     Where to find the standard builtin classes, such as
1355
     `java.lang.String'.
1356
 
1357
`--extdirs=PATH'
1358
     For each directory in the PATH, place the contents of that
1359
     directory at the end of the class path.
1360
 
1361
`CLASSPATH'
1362
     This is an environment variable which holds a list of paths.
1363
 
1364
   The final class path is constructed like so:
1365
 
1366
   * First come all directories specified via `-I'.
1367
 
1368
   * If `--classpath' is specified, its value is appended.  Otherwise,
1369
     if the `CLASSPATH' environment variable is specified, then its
1370
     value is appended.  Otherwise, the current directory (`"."') is
1371
     appended.
1372
 
1373
   * If `--bootclasspath' was specified, append its value.  Otherwise,
1374
     append the built-in system directory, `libgcj.jar'.
1375
 
1376
   * Finally, if `--extdirs' was specified, append the contents of the
1377
     specified directories at the end of the class path.  Otherwise,
1378
     append the contents of the built-in extdirs at
1379
     `$(prefix)/share/java/ext'.
1380
 
1381
   The classfile built by `gcj' for the class `java.lang.Object' (and
1382
placed in `libgcj.jar') contains a special zero length attribute
1383
`gnu.gcj.gcj-compiled'. The compiler looks for this attribute when
1384
loading `java.lang.Object' and will report an error if it isn't found,
1385
unless it compiles to bytecode (the option
1386
`-fforce-classes-archive-check' can be used to override this behavior
1387
in this particular case.)
1388
 
1389
`-fforce-classes-archive-check'
1390
     This forces the compiler to always check for the special zero
1391
     length attribute `gnu.gcj.gcj-compiled' in `java.lang.Object' and
1392
     issue an error if it isn't found.
1393
 
1394
`-fsource=VERSION'
1395
     This option is used to choose the source version accepted by
1396
     `gcj'.  The default is `1.5'.
1397
 
1398

1399
File: gcj.info,  Node: Encodings,  Next: Warnings,  Prev: Input Options,  Up: Invoking gcj
1400
 
1401
1.3 Encodings
1402
=============
1403
 
1404
The Java programming language uses Unicode throughout.  In an effort to
1405
integrate well with other locales, `gcj' allows `.java' files to be
1406
written using almost any encoding.  `gcj' knows how to convert these
1407
encodings into its internal encoding at compile time.
1408
 
1409
   You can use the `--encoding=NAME' option to specify an encoding (of
1410
a particular character set) to use for source files.  If this is not
1411
specified, the default encoding comes from your current locale.  If
1412
your host system has insufficient locale support, then `gcj' assumes
1413
the default encoding to be the `UTF-8' encoding of Unicode.
1414
 
1415
   To implement `--encoding', `gcj' simply uses the host platform's
1416
`iconv' conversion routine.  This means that in practice `gcj' is
1417
limited by the capabilities of the host platform.
1418
 
1419
   The names allowed for the argument `--encoding' vary from platform
1420
to platform (since they are not standardized anywhere).  However, `gcj'
1421
implements the encoding named `UTF-8' internally, so if you choose to
1422
use this for your source files you can be assured that it will work on
1423
every host.
1424
 
1425

1426
File: gcj.info,  Node: Warnings,  Next: Linking,  Prev: Encodings,  Up: Invoking gcj
1427
 
1428
1.4 Warnings
1429
============
1430
 
1431
`gcj' implements several warnings.  As with other generic `gcc'
1432
warnings, if an option of the form `-Wfoo' enables a warning, then
1433
`-Wno-foo' will disable it.  Here we've chosen to document the form of
1434
the warning which will have an effect - the default being the opposite
1435
of what is listed.
1436
 
1437
`-Wredundant-modifiers'
1438
     With this flag, `gcj' will warn about redundant modifiers.  For
1439
     instance, it will warn if an interface method is declared `public'.
1440
 
1441
`-Wextraneous-semicolon'
1442
     This causes `gcj' to warn about empty statements.  Empty statements
1443
     have been deprecated.
1444
 
1445
`-Wno-out-of-date'
1446
     This option will cause `gcj' not to warn when a source file is
1447
     newer than its matching class file.  By default `gcj' will warn
1448
     about this.
1449
 
1450
`-Wno-deprecated'
1451
     Warn if a deprecated class, method, or field is referred to.
1452
 
1453
`-Wunused'
1454
     This is the same as `gcc''s `-Wunused'.
1455
 
1456
`-Wall'
1457
     This is the same as `-Wredundant-modifiers -Wextraneous-semicolon
1458
     -Wunused'.
1459
 
1460

1461
File: gcj.info,  Node: Linking,  Next: Code Generation,  Prev: Warnings,  Up: Invoking gcj
1462
 
1463
1.5 Linking
1464
===========
1465
 
1466
To turn a Java application into an executable program, you need to link
1467
it with the needed libraries, just as for C or C++.  The linker by
1468
default looks for a global function named `main'.  Since Java does not
1469
have global functions, and a collection of Java classes may have more
1470
than one class with a `main' method, you need to let the linker know
1471
which of those `main' methods it should invoke when starting the
1472
application.  You can do that in any of these ways:
1473
 
1474
   * Specify the class containing the desired `main' method when you
1475
     link the application, using the `--main' flag, described below.
1476
 
1477
   * Link the Java package(s) into a shared library (dll) rather than an
1478
     executable.  Then invoke the application using the `gij' program,
1479
     making sure that `gij' can find the libraries it needs.
1480
 
1481
   * Link the Java packages(s) with the flag `-lgij', which links in
1482
     the `main' routine from the `gij' command.  This allows you to
1483
     select the class whose `main' method you want to run when you run
1484
     the application.  You can also use other `gij' flags, such as `-D'
1485
     flags to set properties.  Using the `-lgij' library (rather than
1486
     the `gij' program of the previous mechanism) has some advantages:
1487
     it is compatible with static linking, and does not require
1488
     configuring or installing libraries.
1489
 
1490
   These `gij' options relate to linking an executable:
1491
 
1492
`--main=CLASSNAME'
1493
     This option is used when linking to specify the name of the class
1494
     whose `main' method should be invoked when the resulting
1495
     executable is run.
1496
 
1497
`-DNAME[=VALUE]'
1498
     This option can only be used with `--main'.  It defines a system
1499
     property named NAME with value VALUE.  If VALUE is not specified
1500
     then it defaults to the empty string.  These system properties are
1501
     initialized at the program's startup and can be retrieved at
1502
     runtime using the `java.lang.System.getProperty' method.
1503
 
1504
`-lgij'
1505
     Create an application whose command-line processing is that of the
1506
     `gij' command.
1507
 
1508
     This option is an alternative to using `--main'; you cannot use
1509
     both.
1510
 
1511
`-static-libgcj'
1512
     This option causes linking to be done against a static version of
1513
     the libgcj runtime library.  This option is only available if
1514
     corresponding linker support exists.
1515
 
1516
     *Caution:* Static linking of libgcj may cause essential parts of
1517
     libgcj to be omitted.  Some parts of libgcj use reflection to load
1518
     classes at runtime.  Since the linker does not see these
1519
     references at link time, it can omit the referred to classes.  The
1520
     result is usually (but not always) a `ClassNotFoundException'
1521
     being thrown at runtime. Caution must be used when using this
1522
     option.  For more details see:
1523
     `http://gcc.gnu.org/wiki/Statically%20linking%20libgcj'
1524
 
1525

1526
File: gcj.info,  Node: Code Generation,  Next: Configure-time Options,  Prev: Linking,  Up: Invoking gcj
1527
 
1528
1.6 Code Generation
1529
===================
1530
 
1531
In addition to the many `gcc' options controlling code generation,
1532
`gcj' has several options specific to itself.
1533
 
1534
`-C'
1535
     This option is used to tell `gcj' to generate bytecode (`.class'
1536
     files) rather than object code.
1537
 
1538
`--resource RESOURCE-NAME'
1539
     This option is used to tell `gcj' to compile the contents of a
1540
     given file to object code so it may be accessed at runtime with
1541
     the core protocol handler as `core:/RESOURCE-NAME'.  Note that
1542
     RESOURCE-NAME is the name of the resource as found at runtime; for
1543
     instance, it could be used in a call to `ResourceBundle.getBundle'.
1544
     The actual file name to be compiled this way must be specified
1545
     separately.
1546
 
1547
`-ftarget=VERSION'
1548
     This can be used with `-C' to choose the version of bytecode
1549
     emitted by `gcj'.  The default is `1.5'.  When not generating
1550
     bytecode, this option has no effect.
1551
 
1552
`-d DIRECTORY'
1553
     When used with `-C', this causes all generated `.class' files to
1554
     be put in the appropriate subdirectory of DIRECTORY.  By default
1555
     they will be put in subdirectories of the current working
1556
     directory.
1557
 
1558
`-fno-bounds-check'
1559
     By default, `gcj' generates code which checks the bounds of all
1560
     array indexing operations.  With this option, these checks are
1561
     omitted, which can improve performance for code that uses arrays
1562
     extensively.  Note that this can result in unpredictable behavior
1563
     if the code in question actually does violate array bounds
1564
     constraints.  It is safe to use this option if you are sure that
1565
     your code will never throw an `ArrayIndexOutOfBoundsException'.
1566
 
1567
`-fno-store-check'
1568
     Don't generate array store checks.  When storing objects into
1569
     arrays, a runtime check is normally generated in order to ensure
1570
     that the object is assignment compatible with the component type
1571
     of the array (which may not be known at compile-time).  With this
1572
     option, these checks are omitted.  This can improve performance
1573
     for code which stores objects into arrays frequently.  It is safe
1574
     to use this option if you are sure your code will never throw an
1575
     `ArrayStoreException'.
1576
 
1577
`-fjni'
1578
     With `gcj' there are two options for writing native methods: CNI
1579
     and JNI.  By default `gcj' assumes you are using CNI.  If you are
1580
     compiling a class with native methods, and these methods are
1581
     implemented using JNI, then you must use `-fjni'.  This option
1582
     causes `gcj' to generate stubs which will invoke the underlying JNI
1583
     methods.
1584
 
1585
`-fno-assert'
1586
     Don't recognize the `assert' keyword.  This is for compatibility
1587
     with older versions of the language specification.
1588
 
1589
`-fno-optimize-static-class-initialization'
1590
     When the optimization level is greater or equal to `-O2', `gcj'
1591
     will try to optimize the way calls into the runtime are made to
1592
     initialize static classes upon their first use (this optimization
1593
     isn't carried out if `-C' was specified.) When compiling to native
1594
     code, `-fno-optimize-static-class-initialization' will turn this
1595
     optimization off, regardless of the optimization level in use.
1596
 
1597
`--disable-assertions[=CLASS-OR-PACKAGE]'
1598
     Don't include code for checking assertions in the compiled code.
1599
     If `=CLASS-OR-PACKAGE' is missing disables assertion code
1600
     generation for all classes, unless overridden by a more specific
1601
     `--enable-assertions' flag.  If CLASS-OR-PACKAGE is a class name,
1602
     only disables generating assertion checks within the named class
1603
     or its inner classes.  If CLASS-OR-PACKAGE is a package name,
1604
     disables generating assertion checks within the named package or a
1605
     subpackage.
1606
 
1607
     By default, assertions are enabled when generating class files or
1608
     when not optimizing, and disabled when generating optimized
1609
     binaries.
1610
 
1611
`--enable-assertions[=CLASS-OR-PACKAGE]'
1612
     Generates code to check assertions.  The option is perhaps
1613
     misnamed, as you still need to turn on assertion checking at
1614
     run-time, and we don't support any easy way to do that.  So this
1615
     flag isn't very useful yet, except to partially override
1616
     `--disable-assertions'.
1617
 
1618
`-findirect-dispatch'
1619
     `gcj' has a special binary compatibility ABI, which is enabled by
1620
     the `-findirect-dispatch' option.  In this mode, the code
1621
     generated by `gcj' honors the binary compatibility guarantees in
1622
     the Java Language Specification, and the resulting object files do
1623
     not need to be directly linked against their dependencies.
1624
     Instead, all dependencies are looked up at runtime.  This allows
1625
     free mixing of interpreted and compiled code.
1626
 
1627
     Note that, at present, `-findirect-dispatch' can only be used when
1628
     compiling `.class' files.  It will not work when compiling from
1629
     source.  CNI also does not yet work with the binary compatibility
1630
     ABI.  These restrictions will be lifted in some future release.
1631
 
1632
     However, if you compile CNI code with the standard ABI, you can
1633
     call it from code built with the binary compatibility ABI.
1634
 
1635
`-fbootstrap-classes'
1636
     This option can be use to tell `libgcj' that the compiled classes
1637
     should be loaded by the bootstrap loader, not the system class
1638
     loader.  By default, if you compile a class and link it into an
1639
     executable, it will be treated as if it was loaded using the
1640
     system class loader.  This is convenient, as it means that things
1641
     like `Class.forName()' will search `CLASSPATH' to find the desired
1642
     class.
1643
 
1644
`-freduced-reflection'
1645
     This option causes the code generated by `gcj' to contain a
1646
     reduced amount of the class meta-data used to support runtime
1647
     reflection. The cost of this savings is the loss of the ability to
1648
     use certain reflection capabilities of the standard Java runtime
1649
     environment. When set all meta-data except for that which is
1650
     needed to obtain correct runtime semantics is eliminated.
1651
 
1652
     For code that does not use reflection (i.e. serialization, RMI,
1653
     CORBA or call methods in the `java.lang.reflect' package),
1654
     `-freduced-reflection' will result in proper operation with a
1655
     savings in executable code size.
1656
 
1657
     JNI (`-fjni') and the binary compatibility ABI
1658
     (`-findirect-dispatch') do not work properly without full
1659
     reflection meta-data.  Because of this, it is an error to use
1660
     these options with `-freduced-reflection'.
1661
 
1662
     *Caution:* If there is no reflection meta-data, code that uses a
1663
     `SecurityManager' may not work properly.  Also calling
1664
     `Class.forName()' may fail if the calling method has no reflection
1665
     meta-data.
1666
 
1667
 
1668

1669
File: gcj.info,  Node: Configure-time Options,  Prev: Code Generation,  Up: Invoking gcj
1670
 
1671
1.7 Configure-time Options
1672
==========================
1673
 
1674
Some `gcj' code generations options affect the resulting ABI, and so
1675
can only be meaningfully given when `libgcj', the runtime package, is
1676
configured.  `libgcj' puts the appropriate options from this group into
1677
a `spec' file which is read by `gcj'.  These options are listed here
1678
for completeness; if you are using `libgcj' then you won't want to
1679
touch these options.
1680
 
1681
`-fuse-boehm-gc'
1682
     This enables the use of the Boehm GC bitmap marking code.  In
1683
     particular this causes `gcj' to put an object marking descriptor
1684
     into each vtable.
1685
 
1686
`-fhash-synchronization'
1687
     By default, synchronization data (the data used for `synchronize',
1688
     `wait', and `notify') is pointed to by a word in each object.
1689
     With this option `gcj' assumes that this information is stored in a
1690
     hash table and not in the object itself.
1691
 
1692
`-fuse-divide-subroutine'
1693
     On some systems, a library routine is called to perform integer
1694
     division.  This is required to get exception handling correct when
1695
     dividing by zero.
1696
 
1697
`-fcheck-references'
1698
     On some systems it's necessary to insert inline checks whenever
1699
     accessing an object via a reference.  On other systems you won't
1700
     need this because null pointer accesses are caught automatically
1701
     by the processor.
1702
 
1703
`-fuse-atomic-builtins'
1704
     On some systems, gcc can generate code for built-in atomic
1705
     operations.  Use this option to force gcj to use these builtins
1706
     when compiling Java code.  Where this capability is present it
1707
     should be automatically detected, so you won't usually need to use
1708
     this option.
1709
 
1710
 
1711

1712
File: gcj.info,  Node: Compatibility,  Next: Invoking jcf-dump,  Prev: Invoking gcj,  Up: Top
1713
 
1714
2 Compatibility with the Java Platform
1715
**************************************
1716
 
1717
As we believe it is important that the Java platform not be fragmented,
1718
`gcj' and `libgcj' try to conform to the relevant Java specifications.
1719
However, limited manpower and incomplete and unclear documentation work
1720
against us.  So, there are caveats to using `gcj'.
1721
 
1722
* Menu:
1723
 
1724
* Limitations::
1725
* Extensions::
1726
 
1727

1728
File: gcj.info,  Node: Limitations,  Next: Extensions,  Up: Compatibility
1729
 
1730
2.1 Standard features not yet supported
1731
=======================================
1732
 
1733
This list of compatibility issues is by no means complete.
1734
 
1735
   * `gcj' implements the JDK 1.2 language.  It supports inner classes
1736
     and the new 1.4 `assert' keyword.  It does not yet support the
1737
     Java 2 `strictfp' keyword (it recognizes the keyword but ignores
1738
     it).
1739
 
1740
   * `libgcj' is largely compatible with the JDK 1.2 libraries.
1741
     However, `libgcj' is missing many packages, most notably
1742
     `java.awt'.  There are also individual missing classes and methods.
1743
     We currently do not have a list showing differences between
1744
     `libgcj' and the Java 2 platform.
1745
 
1746
   * Sometimes the `libgcj' implementation of a method or class differs
1747
     from the JDK implementation.  This is not always a bug.  Still, if
1748
     it affects you, it probably makes sense to report it so that we
1749
     can discuss the appropriate response.
1750
 
1751
   * `gcj' does not currently allow for piecemeal replacement of
1752
     components within `libgcj'. Unfortunately, programmers often want
1753
     to use newer versions of certain packages, such as those provided
1754
     by the Apache Software Foundation's Jakarta project.  This has
1755
     forced us to place the `org.w3c.dom' and `org.xml.sax' packages
1756
     into their own libraries, separate from `libgcj'.  If you intend to
1757
     use these classes, you must link them explicitly with
1758
     `-l-org-w3c-dom' and `-l-org-xml-sax'.  Future versions of `gcj'
1759
     may not have this restriction.
1760
 
1761

1762
File: gcj.info,  Node: Extensions,  Prev: Limitations,  Up: Compatibility
1763
 
1764
2.2 Extra features unique to gcj
1765
================================
1766
 
1767
The main feature of `gcj' is that it can compile programs written in
1768
the Java programming language to native code.  Most extensions that
1769
have been added are to facilitate this functionality.
1770
 
1771
   * `gcj' makes it easy and efficient to mix code written in Java and
1772
     C++.  *Note About CNI::, for more info on how to use this in your
1773
     programs.
1774
 
1775
   * When you compile your classes into a shared library using
1776
     `-findirect-dispatch' then add them to the system-wide classmap.db
1777
     file using `gcj-dbtool', they will be automatically loaded by the
1778
     `libgcj' system classloader.  This is the new, preferred
1779
     classname-to-library resolution mechanism.  *Note Invoking
1780
     gcj-dbtool::, for more information on using the classmap database.
1781
 
1782
   * The old classname-to-library lookup mechanism is still supported
1783
     through the `gnu.gcj.runtime.VMClassLoader.library_control'
1784
     property, but it is deprecated and will likely be removed in some
1785
     future release.  When trying to load a class `gnu.pkg.SomeClass'
1786
     the system classloader will first try to load the shared library
1787
     `lib-gnu-pkg-SomeClass.so', if that fails to load the class then
1788
     it will try to load `lib-gnu-pkg.so' and finally when the class is
1789
     still not loaded it will try to load `lib-gnu.so'.  Note that all
1790
     `.'s will be transformed into `-'s and that searching for inner
1791
     classes starts with their outermost outer class.  If the class
1792
     cannot be found this way the system classloader tries to use the
1793
     `libgcj' bytecode interpreter to load the class from the standard
1794
     classpath.  This process can be controlled to some degree via the
1795
     `gnu.gcj.runtime.VMClassLoader.library_control' property; *Note
1796
     libgcj Runtime Properties::.
1797
 
1798
   * `libgcj' includes a special `gcjlib' URL type.  A URL of this form
1799
     is like a `jar' URL, and looks like
1800
     `gcjlib:/path/to/shared/library.so!/path/to/resource'.  An access
1801
     to one of these URLs causes the shared library to be `dlopen()'d,
1802
     and then the resource is looked for in that library.  These URLs
1803
     are most useful when used in conjunction with
1804
     `java.net.URLClassLoader'.  Note that, due to implementation
1805
     limitations, currently any such URL can be accessed by only one
1806
     class loader, and libraries are never unloaded.  This means some
1807
     care must be exercised to make sure that a `gcjlib' URL is not
1808
     accessed by more than one class loader at once.  In a future
1809
     release this limitation will be lifted, and such libraries will be
1810
     mapped privately.
1811
 
1812
   * A program compiled by `gcj' will examine the `GCJ_PROPERTIES'
1813
     environment variable and change its behavior in some ways.  In
1814
     particular `GCJ_PROPERTIES' holds a list of assignments to global
1815
     properties, such as would be set with the `-D' option to `java'.
1816
     For instance, `java.compiler=gcj' is a valid (but currently
1817
     meaningless) setting.
1818
 
1819
 
1820

1821
File: gcj.info,  Node: Invoking jcf-dump,  Next: Invoking gij,  Prev: Compatibility,  Up: Top
1822
 
1823
3 Invoking jcf-dump
1824
*******************
1825
 
1826
This is a class file examiner, similar to `javap'.  It will print
1827
information about a number of classes, which are specified by class name
1828
or file name.
1829
 
1830
`-c'
1831
     Disassemble method bodies.  By default method bodies are not
1832
     printed.
1833
 
1834
`--print-constants'
1835
     Print the constant pool.  When printing a reference to a constant
1836
     also print its index in the constant pool.
1837
 
1838
`--javap'
1839
     Generate output in `javap' format.  The implementation of this
1840
     feature is very incomplete.
1841
 
1842
`--classpath=PATH'
1843
`--CLASSPATH=PATH'
1844
`-IDIRECTORY'
1845
`-o FILE'
1846
     These options as the same as the corresponding `gcj' options.
1847
 
1848
`--help'
1849
     Print help, then exit.
1850
 
1851
`--version'
1852
     Print version number, then exit.
1853
 
1854
`-v, --verbose'
1855
     Print extra information while running.  Implies
1856
     `--print-constants'.
1857
 
1858

1859
File: gcj.info,  Node: Invoking gij,  Next: Invoking gcj-dbtool,  Prev: Invoking jcf-dump,  Up: Top
1860
 
1861
4 Invoking gij
1862
**************
1863
 
1864
`gij' is a Java bytecode interpreter included with `libgcj'.  `gij' is
1865
not available on every platform; porting it requires a small amount of
1866
assembly programming which has not been done for all the targets
1867
supported by `gcj'.
1868
 
1869
   The primary argument to `gij' is the name of a class or, with
1870
`-jar', a jar file.  Options before this argument are interpreted by
1871
`gij'; remaining options are passed to the interpreted program.
1872
 
1873
   If a class name is specified and this class does not have a `main'
1874
method with the appropriate signature (a `static void' method with a
1875
`String[]' as its sole argument), then `gij' will print an error and
1876
exit.
1877
 
1878
   If a jar file is specified then `gij' will use information in it to
1879
determine which class' `main' method will be invoked.
1880
 
1881
   `gij' will invoke the `main' method with all the remaining
1882
command-line options.
1883
 
1884
   Note that `gij' is not limited to interpreting code.  Because
1885
`libgcj' includes a class loader which can dynamically load shared
1886
objects, it is possible to give `gij' the name of a class which has
1887
been compiled and put into a shared library on the class path.
1888
 
1889
`-cp PATH'
1890
`-classpath PATH'
1891
     Set the initial class path.  The class path is used for finding
1892
     class and resource files.  If specified, this option overrides the
1893
     `CLASSPATH' environment variable.  Note that this option is
1894
     ignored if `-jar' is used.
1895
 
1896
`-DNAME[=VALUE]'
1897
     This defines a system property named NAME with value VALUE.  If
1898
     VALUE is not specified then it defaults to the empty string.
1899
     These system properties are initialized at the program's startup
1900
     and can be retrieved at runtime using the
1901
     `java.lang.System.getProperty' method.
1902
 
1903
`-ms=NUMBER'
1904
     Equivalent to `-Xms'.
1905
 
1906
`-mx=NUMBER'
1907
     Equivalent to `-Xmx'.
1908
 
1909
`-noverify'
1910
     Do not verify compliance of bytecode with the VM specification. In
1911
     addition, this option disables type verification which is
1912
     otherwise performed on BC-ABI compiled code.
1913
 
1914
`-X'
1915
`-XARGUMENT'
1916
     Supplying `-X' by itself will cause `gij' to list all the
1917
     supported `-X' options.  Currently these options are supported:
1918
 
1919
    `-XmsSIZE'
1920
          Set the initial heap size.
1921
 
1922
    `-XmxSIZE'
1923
          Set the maximum heap size.
1924
 
1925
    `-XssSIZE'
1926
          Set the thread stack size.
1927
 
1928
     Unrecognized `-X' options are ignored, for compatibility with
1929
     other runtimes.
1930
 
1931
`-jar'
1932
     This indicates that the name passed to `gij' should be interpreted
1933
     as the name of a jar file, not a class.
1934
 
1935
`--help'
1936
`-?'
1937
     Print help, then exit.
1938
 
1939
`--showversion'
1940
     Print version number and continue.
1941
 
1942
`--fullversion'
1943
     Print detailed version information, then exit.
1944
 
1945
`--version'
1946
     Print version number, then exit.
1947
 
1948
`-verbose'
1949
`-verbose:class'
1950
     Each time a class is initialized, print a short message on
1951
     standard error.
1952
 
1953
   `gij' also recognizes and ignores the following options, for
1954
compatibility with existing application launch scripts: `-client',
1955
`-server', `-hotspot', `-jrockit', `-agentlib', `-agentpath', `-debug',
1956
`-d32', `-d64', `-javaagent', `-noclassgc', `-verify', and
1957
`-verifyremote'.
1958
 
1959

1960
File: gcj.info,  Node: Invoking gcj-dbtool,  Next: Invoking jv-convert,  Prev: Invoking gij,  Up: Top
1961
 
1962
5 Invoking gcj-dbtool.
1963
**********************
1964
 
1965
`gcj-dbtool' is a tool for creating and manipulating class file mapping
1966
databases.  `libgcj' can use these databases to find a shared library
1967
corresponding to the bytecode representation of a class.  This
1968
functionality is useful for ahead-of-time compilation of a program that
1969
has no knowledge of `gcj'.
1970
 
1971
   `gcj-dbtool' works best if all the jar files added to it are
1972
compiled using `-findirect-dispatch'.
1973
 
1974
   Note that `gcj-dbtool' is currently available as "preview
1975
technology".  We believe it is a reasonable way to allow
1976
application-transparent ahead-of-time compilation, but this is an
1977
unexplored area.  We welcome your comments.
1978
 
1979
`-n DBFILE [SIZE]'
1980
     This creates a new database.  Currently, databases cannot be
1981
     resized; you can choose a larger initial size if desired.  The
1982
     default size is 32,749.
1983
 
1984
`-a DBFILE JARFILE LIB'
1985
`-f DBFILE JARFILE LIB'
1986
     This adds a jar file to the database.  For each class file in the
1987
     jar, a cryptographic signature of the bytecode representation of
1988
     the class is recorded in the database.  At runtime, a class is
1989
     looked up by its signature and the compiled form of the class is
1990
     looked for in the corresponding shared library.  The `-a' option
1991
     will verify that LIB exists before adding it to the database; `-f'
1992
     skips this check.
1993
 
1994
`[`-'][`-0'] -m DBFILE DBFILE,[DBFILE]'
1995
     Merge a number of databases.  The output database overwrites any
1996
     existing database.  To add databases into an existing database,
1997
     include the destination in the list of sources.
1998
 
1999
     If `-' or `-0' are used, the list of files to read is taken from
2000
     standard input instead of the command line.  For `-0', Input
2001
     filenames are terminated by a null character instead of by
2002
     whitespace.  Useful when arguments might contain white space.  The
2003
     GNU find -print0 option produces input suitable for this mode.
2004
 
2005
`-t DBFILE'
2006
     Test a database.
2007
 
2008
`-l DBFILE'
2009
     List the contents of a database.
2010
 
2011
`-p'
2012
     Print the name of the default database.  If there is no default
2013
     database, this prints a blank line.  If LIBDIR is specified, use
2014
     it instead of the default library directory component of the
2015
     database name.
2016
 
2017
`--help'
2018
     Print a help message, then exit.
2019
 
2020
`--version'
2021
`-v'
2022
     Print version information, then exit.
2023
 
2024
 
2025

2026
File: gcj.info,  Node: Invoking jv-convert,  Next: Invoking grmic,  Prev: Invoking gcj-dbtool,  Up: Top
2027
 
2028
6 Invoking jv-convert
2029
*********************
2030
 
2031
`jv-convert' [`OPTION'] ... [INPUTFILE [OUTPUTFILE]]
2032
 
2033
   `jv-convert' is a utility included with `libgcj' which converts a
2034
file from one encoding to another.  It is similar to the Unix `iconv'
2035
utility.
2036
 
2037
   The encodings supported by `jv-convert' are platform-dependent.
2038
Currently there is no way to get a list of all supported encodings.
2039
 
2040
`--encoding NAME'
2041
`--from NAME'
2042
     Use NAME as the input encoding.  The default is the current
2043
     locale's encoding.
2044
 
2045
`--to NAME'
2046
     Use NAME as the output encoding.  The default is the `JavaSrc'
2047
     encoding; this is ASCII with `\u' escapes for non-ASCII characters.
2048
 
2049
`-i FILE'
2050
     Read from FILE.  The default is to read from standard input.
2051
 
2052
`-o FILE'
2053
     Write to FILE.  The default is to write to standard output.
2054
 
2055
`--reverse'
2056
     Swap the input and output encodings.
2057
 
2058
`--help'
2059
     Print a help message, then exit.
2060
 
2061
`--version'
2062
     Print version information, then exit.
2063
 
2064

2065
File: gcj.info,  Node: Invoking grmic,  Next: Invoking gc-analyze,  Prev: Invoking jv-convert,  Up: Top
2066
 
2067
7 Invoking grmic
2068
****************
2069
 
2070
`grmic' [`OPTION'] ... CLASS ...
2071
 
2072
   `grmic' is a utility included with `libgcj' which generates stubs
2073
for remote objects.
2074
 
2075
   Note that this program isn't yet fully compatible with the JDK
2076
`grmic'.  Some options, such as `-classpath', are recognized but
2077
currently ignored.  We have left these options undocumented for now.
2078
 
2079
   Long options can also be given with a GNU-style leading `--'.  For
2080
instance, `--help' is accepted.
2081
 
2082
`-keep'
2083
`-keepgenerated'
2084
     By default, `grmic' deletes intermediate files.  Either of these
2085
     options causes it not to delete such files.
2086
 
2087
`-v1.1'
2088
     Cause `grmic' to create stubs and skeletons for the 1.1 protocol
2089
     version.
2090
 
2091
`-vcompat'
2092
     Cause `grmic' to create stubs and skeletons compatible with both
2093
     the 1.1 and 1.2 protocol versions.  This is the default.
2094
 
2095
`-v1.2'
2096
     Cause `grmic' to create stubs and skeletons for the 1.2 protocol
2097
     version.
2098
 
2099
`-nocompile'
2100
     Don't compile the generated files.
2101
 
2102
`-verbose'
2103
     Print information about what `grmic' is doing.
2104
 
2105
`-d DIRECTORY'
2106
     Put output files in DIRECTORY.  By default the files are put in
2107
     the current working directory.
2108
 
2109
`-help'
2110
     Print a help message, then exit.
2111
 
2112
`-version'
2113
     Print version information, then exit.
2114
 
2115

2116
File: gcj.info,  Node: Invoking gc-analyze,  Next: Invoking aot-compile,  Prev: Invoking grmic,  Up: Top
2117
 
2118
8 Invoking gc-analyze
2119
*********************
2120
 
2121
`gc-analyze' [`OPTION'] ... [FILE]
2122
 
2123
   `gc-analyze' prints an analysis of a GC memory dump to standard out.
2124
 
2125
   The memory dumps may be created by calling
2126
`gnu.gcj.util.GCInfo.enumerate(String namePrefix)' from java code.  A
2127
memory dump will be created on an out of memory condition if
2128
`gnu.gcj.util.GCInfo.setOOMDump(String namePrefix)' is called before
2129
the out of memory occurs.
2130
 
2131
   Running this program will create two files: `TestDump001' and
2132
`TestDump001.bytes'.
2133
 
2134
     import gnu.gcj.util.*;
2135
     import java.util.*;
2136
 
2137
     public class GCDumpTest
2138
     {
2139
         static public void main(String args[])
2140
         {
2141
             ArrayList l = new ArrayList(1000);
2142
 
2143
             for (int i = 1; i < 1500; i++) {
2144
                 l.add("This is string #" + i);
2145
             }
2146
             GCInfo.enumerate("TestDump");
2147
         }
2148
     }
2149
 
2150
   The memory dump may then be displayed by running:
2151
 
2152
     gc-analyze -v TestDump001
2153
 
2154
`--verbose'
2155
`-v'
2156
     Verbose output.
2157
 
2158
`-p TOOL-PREFIX'
2159
     Prefix added to the names of the `nm' and `readelf' commands.
2160
 
2161
`-d DIRECTORY'
2162
     Directory that contains the executable and shared libraries used
2163
     when the dump was generated.
2164
 
2165
`--help'
2166
     Print a help message, then exit.
2167
 
2168
`--version'
2169
     Print version information, then exit.
2170
 
2171

2172
File: gcj.info,  Node: Invoking aot-compile,  Next: Invoking rebuild-gcj-db,  Prev: Invoking gc-analyze,  Up: Top
2173
 
2174
9 Invoking aot-compile
2175
**********************
2176
 
2177
`aot-compile' is a script that searches a directory for Java bytecode
2178
(as class files, or in jars) and uses `gcj' to compile it to native
2179
code and generate the databases from it.
2180
 
2181
`-M, --make=PATH'
2182
     Specify the path to the `make' executable to use.
2183
 
2184
`-C, --gcj=PATH'
2185
     Specify the path to the `gcj' executable to use.
2186
 
2187
`-D, --dbtool=PATH'
2188
     Specify the path to the `gcj-dbtool' executable to use.
2189
 
2190
`-m, --makeflags=FLAGS'
2191
     Specify flags to pass to `make' during the build.
2192
 
2193
`-c, --gcjflags=FLAGS'
2194
     Specify flags to pass to `gcj' during compilation, in addition to
2195
     '-fPIC -findirect-dispatch -fjni'.
2196
 
2197
`-l, --ldflags=FLAGS'
2198
     Specify flags to pass to `gcj' during linking, in addition to
2199
     '-Wl,-Bsymbolic'.
2200
 
2201
`-e, --exclude=PATH'
2202
     Do not compile PATH.
2203
 
2204
 
2205

2206
File: gcj.info,  Node: Invoking rebuild-gcj-db,  Next: About CNI,  Prev: Invoking aot-compile,  Up: Top
2207
 
2208
10 Invoking rebuild-gcj-db
2209
**************************
2210
 
2211
`rebuild-gcj-db' is a script that merges the per-solib databases made by
2212
`aot-compile' into one system-wide database so `gij' can find the
2213
solibs.
2214
 
2215

2216
File: gcj.info,  Node: About CNI,  Next: System properties,  Prev: Invoking rebuild-gcj-db,  Up: Top
2217
 
2218
11 About CNI
2219
************
2220
 
2221
This documents CNI, the Compiled Native Interface, which is is a
2222
convenient way to write Java native methods using C++.  This is a more
2223
efficient, more convenient, but less portable alternative to the
2224
standard JNI (Java Native Interface).
2225
 
2226
* Menu:
2227
 
2228
* Basic concepts::              Introduction to using CNI.
2229
* Packages::                    How packages are mapped to C++.
2230
* Primitive types::             Handling primitive Java types in C++.
2231
* Reference types::             Handling Java reference types in C++.
2232
* Interfaces::                  How Java interfaces map to C++.
2233
* Objects and Classes::         C++ and Java classes.
2234
* Class Initialization::        How objects are initialized.
2235
* Object allocation::           How to create Java objects in C++.
2236
* Memory allocation::           How to allocate and free memory.
2237
* Arrays::                      Dealing with Java arrays in C++.
2238
* Methods::                     Java methods in C++.
2239
* Strings::                     Information about Java Strings.
2240
* Mixing with C++::             How CNI can interoperate with C++.
2241
* Exception Handling::          How exceptions are handled.
2242
* Synchronization::             Synchronizing between Java and C++.
2243
* Invocation::                  Starting the Java runtime from C++.
2244
* Reflection::                  Using reflection from C++.
2245
 
2246

2247
File: gcj.info,  Node: Basic concepts,  Next: Packages,  Up: About CNI
2248
 
2249
11.1 Basic concepts
2250
===================
2251
 
2252
In terms of languages features, Java is mostly a subset of C++.  Java
2253
has a few important extensions, plus a powerful standard class library,
2254
but on the whole that does not change the basic similarity.  Java is a
2255
hybrid object-oriented language, with a few native types, in addition
2256
to class types.  It is class-based, where a class may have static as
2257
well as per-object fields, and static as well as instance methods.
2258
Non-static methods may be virtual, and may be overloaded.  Overloading
2259
is resolved at compile time by matching the actual argument types
2260
against the parameter types.  Virtual methods are implemented using
2261
indirect calls through a dispatch table (virtual function table).
2262
Objects are allocated on the heap, and initialized using a constructor
2263
method.  Classes are organized in a package hierarchy.
2264
 
2265
   All of the listed attributes are also true of C++, though C++ has
2266
extra features (for example in C++ objects may be allocated not just on
2267
the heap, but also statically or in a local stack frame).  Because
2268
`gcj' uses the same compiler technology as G++ (the GNU C++ compiler),
2269
it is possible to make the intersection of the two languages use the
2270
same ABI (object representation and calling conventions).  The key idea
2271
in CNI is that Java objects are C++ objects, and all Java classes are
2272
C++ classes (but not the other way around).  So the most important task
2273
in integrating Java and C++ is to remove gratuitous incompatibilities.
2274
 
2275
   You write CNI code as a regular C++ source file.  (You do have to use
2276
a Java/CNI-aware C++ compiler, specifically a recent version of G++.)
2277
 
2278
A CNI C++ source file must have:
2279
 
2280
     #include 
2281
 
2282
and then must include one header file for each Java class it uses, e.g.:
2283
 
2284
     #include 
2285
     #include 
2286
     #include 
2287
 
2288
These header files are automatically generated by `gcjh'.
2289
 
2290
   CNI provides some functions and macros to make using Java objects and
2291
primitive types from C++ easier.  In general, these CNI functions and
2292
macros start with the `Jv' prefix, for example the function
2293
`JvNewObjectArray'.  This convention is used to avoid conflicts with
2294
other libraries.  Internal functions in CNI start with the prefix
2295
`_Jv_'.  You should not call these; if you find a need to, let us know
2296
and we will try to come up with an alternate solution.
2297
 
2298
11.1.1 Limitations
2299
------------------
2300
 
2301
Whilst a Java class is just a C++ class that doesn't mean that you are
2302
freed from the shackles of Java, a CNI C++ class must adhere to the
2303
rules of the Java programming language.
2304
 
2305
   For example: it is not possible to declare a method in a CNI class
2306
that will take a C string (`char*') as an argument, or to declare a
2307
member variable of some non-Java datatype.
2308
 
2309

2310
File: gcj.info,  Node: Packages,  Next: Primitive types,  Prev: Basic concepts,  Up: About CNI
2311
 
2312
11.2 Packages
2313
=============
2314
 
2315
The only global names in Java are class names, and packages.  A
2316
"package" can contain zero or more classes, and also zero or more
2317
sub-packages.  Every class belongs to either an unnamed package or a
2318
package that has a hierarchical and globally unique name.
2319
 
2320
   A Java package is mapped to a C++ "namespace".  The Java class
2321
`java.lang.String' is in the package `java.lang', which is a
2322
sub-package of `java'.  The C++ equivalent is the class
2323
`java::lang::String', which is in the namespace `java::lang' which is
2324
in the namespace `java'.
2325
 
2326
Here is how you could express this:
2327
 
2328
     (// Declare the class(es), possibly in a header file:
2329
     namespace java {
2330
       namespace lang {
2331
         class Object;
2332
         class String;
2333
         ...
2334
       }
2335
     }
2336
 
2337
     class java::lang::String : public java::lang::Object
2338
     {
2339
       ...
2340
     };
2341
 
2342
The `gcjh' tool automatically generates the necessary namespace
2343
declarations.
2344
 
2345
11.2.1 Leaving out package names
2346
--------------------------------
2347
 
2348
Always using the fully-qualified name of a java class can be tiresomely
2349
verbose.  Using the full qualified name also ties the code to a single
2350
package making code changes necessary should the class move from one
2351
package to another.  The Java `package' declaration specifies that the
2352
following class declarations are in the named package, without having
2353
to explicitly name the full package qualifiers.  The `package'
2354
declaration can be followed by zero or more `import' declarations, which
2355
allows either a single class or all the classes in a package to be
2356
named by a simple identifier.  C++ provides something similar with the
2357
`using' declaration and directive.
2358
 
2359
In Java:
2360
 
2361
     import PACKAGE-NAME.CLASS-NAME;
2362
 
2363
allows the program text to refer to CLASS-NAME as a shorthand for the
2364
fully qualified name: `PACKAGE-NAME.CLASS-NAME'.
2365
 
2366
To achieve the same effect C++, you have to do this:
2367
 
2368
     using PACKAGE-NAME::CLASS-NAME;
2369
 
2370
Java can also cause imports on demand, like this:
2371
 
2372
     import PACKAGE-NAME.*;
2373
 
2374
Doing this allows any class from the package PACKAGE-NAME to be
2375
referred to only by its class-name within the program text.
2376
 
2377
The same effect can be achieved in C++ like this:
2378
 
2379
     using namespace PACKAGE-NAME;
2380
 
2381

2382
File: gcj.info,  Node: Primitive types,  Next: Reference types,  Prev: Packages,  Up: About CNI
2383
 
2384
11.3 Primitive types
2385
====================
2386
 
2387
Java provides 8 "primitives" types which represent integers, floats,
2388
characters and booleans (and also the void type).  C++ has its own very
2389
similar concrete types.  Such types in C++ however are not always
2390
implemented in the same way (an int might be 16, 32 or 64 bits for
2391
example) so CNI provides a special C++ type for each primitive Java
2392
type:
2393
 
2394
*Java type*    *C/C++ typename*   *Description*
2395
`char'         `jchar'            16 bit Unicode character
2396
`boolean'      `jboolean'         logical (true or false) values
2397
`byte'         `jbyte'            8-bit signed integer
2398
`short'        `jshort'           16 bit signed integer
2399
`int'          `jint'             32 bit signed integer
2400
`long'         `jlong'            64 bit signed integer
2401
`float'        `jfloat'           32 bit IEEE floating point number
2402
`double'       `jdouble'          64 bit IEEE floating point number
2403
`void'         `void'             no value
2404
 
2405
   When referring to a Java type You should always use these C++
2406
typenames (e.g.: `jint') to avoid disappointment.
2407
 
2408
11.3.1 Reference types associated with primitive types
2409
------------------------------------------------------
2410
 
2411
In Java each primitive type has an associated reference type, e.g.:
2412
`boolean' has an associated `java.lang.Boolean.TYPE' class.  In order
2413
to make working with such classes easier GCJ provides the macro
2414
`JvPrimClass':
2415
 
2416
 -- macro: JvPrimClass type
2417
     Return a pointer to the `Class' object corresponding to the type
2418
     supplied.
2419
 
2420
          JvPrimClass(void) => java.lang.Void.TYPE
2421
 
2422
 
2423

2424
File: gcj.info,  Node: Reference types,  Next: Interfaces,  Prev: Primitive types,  Up: About CNI
2425
 
2426
11.4 Reference types
2427
====================
2428
 
2429
A Java reference type is treated as a class in C++.  Classes and
2430
interfaces are handled this way.  A Java reference is translated to a
2431
C++ pointer, so for instance a Java `java.lang.String' becomes, in C++,
2432
`java::lang::String *'.
2433
 
2434
   CNI provides a few built-in typedefs for the most common classes:
2435
*Java type*            *C++ typename*     *Description*
2436
`java.lang.Object'     `jobject'          Object type
2437
`java.lang.String'     `jstring'          String type
2438
`java.lang.Class'      `jclass'           Class type
2439
 
2440
   Every Java class or interface has a corresponding `Class' instance.
2441
These can be accessed in CNI via the static `class$' field of a class.
2442
The `class$' field is of type `Class' (and not `Class *'), so you will
2443
typically take the address of it.
2444
 
2445
   Here is how you can refer to the class of `String', which in Java
2446
would be written `String.class':
2447
 
2448
     using namespace java::lang;
2449
     doSomething (&String::class$);
2450
 
2451

2452
File: gcj.info,  Node: Interfaces,  Next: Objects and Classes,  Prev: Reference types,  Up: About CNI
2453
 
2454
11.5 Interfaces
2455
===============
2456
 
2457
A Java class can "implement" zero or more "interfaces", in addition to
2458
inheriting from a single base class.
2459
 
2460
   CNI allows CNI code to implement methods of interfaces.  You can
2461
also call methods through interface references, with some limitations.
2462
 
2463
   CNI doesn't understand interface inheritance at all yet.  So, you
2464
can only call an interface method when the declared type of the field
2465
being called matches the interface which declares that method.  The
2466
workaround is to cast the interface reference to the right
2467
superinterface.
2468
 
2469
   For example if you have:
2470
 
2471
     interface A
2472
     {
2473
       void a();
2474
     }
2475
 
2476
     interface B extends A
2477
     {
2478
       void b();
2479
     }
2480
 
2481
   and declare a variable of type `B' in C++, you can't call `a()'
2482
unless you cast it to an `A' first.
2483
 
2484

2485
File: gcj.info,  Node: Objects and Classes,  Next: Class Initialization,  Prev: Interfaces,  Up: About CNI
2486
 
2487
11.6 Objects and Classes
2488
========================
2489
 
2490
11.6.1 Classes
2491
--------------
2492
 
2493
All Java classes are derived from `java.lang.Object'.  C++ does not
2494
have a unique root class, but we use the C++ class `java::lang::Object'
2495
as the C++ version of the `java.lang.Object' Java class.  All other
2496
Java classes are mapped into corresponding C++ classes derived from
2497
`java::lang::Object'.
2498
 
2499
   Interface inheritance (the `implements' keyword) is currently not
2500
reflected in the C++ mapping.
2501
 
2502
11.6.2 Object fields
2503
--------------------
2504
 
2505
Each object contains an object header, followed by the instance fields
2506
of the class, in order.  The object header consists of a single pointer
2507
to a dispatch or virtual function table.  (There may be extra fields
2508
_in front of_ the object, for example for memory management, but this
2509
is invisible to the application, and the reference to the object points
2510
to the dispatch table pointer.)
2511
 
2512
   The fields are laid out in the same order, alignment, and size as in
2513
C++.  Specifically, 8-bit and 16-bit native types (`byte', `short',
2514
`char', and `boolean') are _not_ widened to 32 bits.  Note that the
2515
Java VM does extend 8-bit and 16-bit types to 32 bits when on the VM
2516
stack or temporary registers.
2517
 
2518
   If you include the `gcjh'-generated header for a class, you can
2519
access fields of Java classes in the _natural_ way.  For example, given
2520
the following Java class:
2521
 
2522
     public class Int
2523
     {
2524
       public int i;
2525
       public Int (int i) { this.i = i; }
2526
       public static Int zero = new Int(0);
2527
     }
2528
 
2529
   you can write:
2530
 
2531
     #include ;
2532
     #include ;
2533
 
2534
     Int*
2535
     mult (Int *p, jint k)
2536
     {
2537
       if (k == 0)
2538
         return Int::zero;  // Static member access.
2539
       return new Int(p->i * k);
2540
     }
2541
 
2542
11.6.3 Access specifiers
2543
------------------------
2544
 
2545
CNI does not strictly enforce the Java access specifiers, because Java
2546
permissions cannot be directly mapped into C++ permission.  Private
2547
Java fields and methods are mapped to private C++ fields and methods,
2548
but other fields and methods are mapped to public fields and methods.
2549
 
2550

2551
File: gcj.info,  Node: Class Initialization,  Next: Object allocation,  Prev: Objects and Classes,  Up: About CNI
2552
 
2553
11.7 Class Initialization
2554
=========================
2555
 
2556
Java requires that each class be automatically initialized at the time
2557
of the first active use.  Initializing a class involves initializing
2558
the static fields, running code in class initializer methods, and
2559
initializing base classes.  There may also be some implementation
2560
specific actions, such as allocating `String' objects corresponding to
2561
string literals in the code.
2562
 
2563
   The GCJ compiler inserts calls to `JvInitClass' at appropriate
2564
places to ensure that a class is initialized when required.  The C++
2565
compiler does not insert these calls automatically--it is the
2566
programmer's responsibility to make sure classes are initialized.
2567
However, this is fairly painless because of the conventions assumed by
2568
the Java system.
2569
 
2570
   First, `libgcj' will make sure a class is initialized before an
2571
instance of that object is created.  This is one of the
2572
responsibilities of the `new' operation.  This is taken care of both in
2573
Java code, and in C++ code.  When G++ sees a `new' of a Java class, it
2574
will call a routine in `libgcj' to allocate the object, and that
2575
routine will take care of initializing the class.  Note however that
2576
this does not happen for Java arrays; you must allocate those using the
2577
appropriate CNI function.  It follows that you can access an instance
2578
field, or call an instance (non-static) method and be safe in the
2579
knowledge that the class and all of its base classes have been
2580
initialized.
2581
 
2582
   Invoking a static method is also safe.  This is because the Java
2583
compiler adds code to the start of a static method to make sure the
2584
class is initialized.  However, the C++ compiler does not add this
2585
extra code.  Hence, if you write a native static method using CNI, you
2586
are responsible for calling `JvInitClass' before doing anything else in
2587
the method (unless you are sure it is safe to leave it out).
2588
 
2589
   Accessing a static field also requires the class of the field to be
2590
initialized.  The Java compiler will generate code to call
2591
`JvInitClass' before getting or setting the field.  However, the C++
2592
compiler will not generate this extra code, so it is your
2593
responsibility to make sure the class is initialized before you access
2594
a static field from C++.
2595
 
2596

2597
File: gcj.info,  Node: Object allocation,  Next: Memory allocation,  Prev: Class Initialization,  Up: About CNI
2598
 
2599
11.8 Object allocation
2600
======================
2601
 
2602
New Java objects are allocated using a "class instance creation
2603
expression", e.g.:
2604
 
2605
     new TYPE ( ... )
2606
 
2607
   The same syntax is used in C++.  The main difference is that C++
2608
objects have to be explicitly deleted; in Java they are automatically
2609
deleted by the garbage collector.  Using CNI, you can allocate a new
2610
Java object using standard C++ syntax and the C++ compiler will allocate
2611
memory from the garbage collector.  If you have overloaded
2612
constructors, the compiler will choose the correct one using standard
2613
C++ overload resolution rules.
2614
 
2615
For example:
2616
 
2617
     java::util::Hashtable *ht = new java::util::Hashtable(120);
2618
 
2619

2620
File: gcj.info,  Node: Memory allocation,  Next: Arrays,  Prev: Object allocation,  Up: About CNI
2621
 
2622
11.9 Memory allocation
2623
======================
2624
 
2625
When allocating memory in CNI methods it is best to handle
2626
out-of-memory conditions by throwing a Java exception.  These functions
2627
are provided for that purpose:
2628
 
2629
 -- Function: void* JvMalloc (jsize SIZE)
2630
     Calls malloc.  Throws `java.lang.OutOfMemoryError' if allocation
2631
     fails.
2632
 
2633
 -- Function: void* JvRealloc (void* PTR, jsize SIZE)
2634
     Calls realloc.  Throws `java.lang.OutOfMemoryError' if
2635
     reallocation fails.
2636
 
2637
 -- Function: void JvFree (void* PTR)
2638
     Calls free.
2639
 
2640

2641
File: gcj.info,  Node: Arrays,  Next: Methods,  Prev: Memory allocation,  Up: About CNI
2642
 
2643
11.10 Arrays
2644
============
2645
 
2646
While in many ways Java is similar to C and C++, it is quite different
2647
in its treatment of arrays.  C arrays are based on the idea of pointer
2648
arithmetic, which would be incompatible with Java's security
2649
requirements.  Java arrays are true objects (array types inherit from
2650
`java.lang.Object').  An array-valued variable is one that contains a
2651
reference (pointer) to an array object.
2652
 
2653
   Referencing a Java array in C++ code is done using the `JArray'
2654
template, which as defined as follows:
2655
 
2656
     class __JArray : public java::lang::Object
2657
     {
2658
     public:
2659
       int length;
2660
     };
2661
 
2662
     template
2663
     class JArray : public __JArray
2664
     {
2665
       T data[0];
2666
     public:
2667
       T& operator[](jint i) { return data[i]; }
2668
     };
2669
 
2670
   There are a number of `typedef's which correspond to `typedef's from
2671
the JNI.  Each is the type of an array holding objects of the relevant
2672
type:
2673
 
2674
     typedef __JArray *jarray;
2675
     typedef JArray *jobjectArray;
2676
     typedef JArray *jbooleanArray;
2677
     typedef JArray *jbyteArray;
2678
     typedef JArray *jcharArray;
2679
     typedef JArray *jshortArray;
2680
     typedef JArray *jintArray;
2681
     typedef JArray *jlongArray;
2682
     typedef JArray *jfloatArray;
2683
     typedef JArray *jdoubleArray;
2684
 
2685
 -- Method on template: T* elements (JArray ARRAY)
2686
     This template function can be used to get a pointer to the
2687
     elements of the `array'.  For instance, you can fetch a pointer to
2688
     the integers that make up an `int[]' like so:
2689
 
2690
          extern jintArray foo;
2691
          jint *intp = elements (foo);
2692
 
2693
     The name of this function may change in the future.
2694
 
2695
 -- Function: jobjectArray JvNewObjectArray (jsize LENGTH, jclass
2696
          KLASS, jobject INIT)
2697
     This creates a new array whose elements have reference type.
2698
     `klass' is the type of elements of the array and `init' is the
2699
     initial value put into every slot in the array.
2700
 
2701
     using namespace java::lang;
2702
     JArray *array
2703
       = (JArray *) JvNewObjectArray(length, &String::class$, NULL);
2704
 
2705
11.10.1 Creating arrays
2706
-----------------------
2707
 
2708
For each primitive type there is a function which can be used to create
2709
a new array of that type.  The name of the function is of the form:
2710
 
2711
     JvNewTYPEArray
2712
 
2713
For example:
2714
 
2715
     JvNewBooleanArray
2716
 
2717
can be used to create an array of Java primitive boolean types.
2718
 
2719
The following function definition is the template for all such
2720
functions:
2721
 
2722
 -- Function: jbooleanArray JvNewBooleanArray (jint LENGTH)
2723
     Creates an array LENGTH indices long.
2724
 
2725
 -- Function: jsize JvGetArrayLength (jarray ARRAY)
2726
     Returns the length of the ARRAY.
2727
 
2728

2729
File: gcj.info,  Node: Methods,  Next: Strings,  Prev: Arrays,  Up: About CNI
2730
 
2731
11.11 Methods
2732
=============
2733
 
2734
Java methods are mapped directly into C++ methods.  The header files
2735
generated by `gcjh' include the appropriate method definitions.
2736
Basically, the generated methods have the same names and
2737
_corresponding_ types as the Java methods, and are called in the
2738
natural manner.
2739
 
2740
11.11.1 Overloading
2741
-------------------
2742
 
2743
Both Java and C++ provide method overloading, where multiple methods in
2744
a class have the same name, and the correct one is chosen (at compile
2745
time) depending on the argument types.  The rules for choosing the
2746
correct method are (as expected) more complicated in C++ than in Java,
2747
but given a set of overloaded methods generated by `gcjh' the C++
2748
compiler will choose the expected one.
2749
 
2750
   Common assemblers and linkers are not aware of C++ overloading, so
2751
the standard implementation strategy is to encode the parameter types
2752
of a method into its assembly-level name.  This encoding is called
2753
"mangling", and the encoded name is the "mangled name".  The same
2754
mechanism is used to implement Java overloading.  For C++/Java
2755
interoperability, it is important that both the Java and C++ compilers
2756
use the _same_ encoding scheme.
2757
 
2758
11.11.2 Static methods
2759
----------------------
2760
 
2761
Static Java methods are invoked in CNI using the standard C++ syntax,
2762
using the `::' operator rather than the `.' operator.
2763
 
2764
For example:
2765
 
2766
     jint i = java::lang::Math::round((jfloat) 2.3);
2767
 
2768
C++ method definition syntax is used to define a static native method.
2769
For example:
2770
 
2771
     #include 
2772
     java::lang::Integer*
2773
     java::lang::Integer::getInteger(jstring str)
2774
     {
2775
       ...
2776
     }
2777
 
2778
11.11.3 Object Constructors
2779
---------------------------
2780
 
2781
Constructors are called implicitly as part of object allocation using
2782
the `new' operator.
2783
 
2784
For example:
2785
 
2786
     java::lang::Integer *x = new java::lang::Integer(234);
2787
 
2788
   Java does not allow a constructor to be a native method.  This
2789
limitation can be coded round however because a constructor can _call_
2790
a native method.
2791
 
2792
11.11.4 Instance methods
2793
------------------------
2794
 
2795
Calling a Java instance method from a C++ CNI method is done using the
2796
standard C++ syntax, e.g.:
2797
 
2798
     // First create the Java object.
2799
     java::lang::Integer *x = new java::lang::Integer(234);
2800
     // Now call a method.
2801
     jint prim_value = x->intValue();
2802
     if (x->longValue == 0)
2803
       ...
2804
 
2805
Defining a Java native instance method is also done the natural way:
2806
 
2807
     #include 
2808
 
2809
     jdouble
2810
     java::lang:Integer::doubleValue()
2811
     {
2812
       return (jdouble) value;
2813
     }
2814
 
2815
11.11.5 Interface methods
2816
-------------------------
2817
 
2818
In Java you can call a method using an interface reference.  This is
2819
supported, but not completely.  *Note Interfaces::.
2820
 
2821

2822
File: gcj.info,  Node: Strings,  Next: Mixing with C++,  Prev: Methods,  Up: About CNI
2823
 
2824
11.12 Strings
2825
=============
2826
 
2827
CNI provides a number of utility functions for working with Java Java
2828
`String' objects.  The names and interfaces are analogous to those of
2829
JNI.
2830
 
2831
 -- Function: jstring JvNewString (const jchar* CHARS, jsize LEN)
2832
     Returns a Java `String' object with characters from the array of
2833
     Unicode characters CHARS up to the index LEN in that array.
2834
 
2835
 -- Function: jstring JvNewStringLatin1 (const char* BYTES, jsize LEN)
2836
     Returns a Java `String' made up of LEN bytes from BYTES.
2837
 
2838
 -- Function: jstring JvNewStringLatin1 (const char* BYTES)
2839
     As above but the length of the `String' is `strlen(BYTES)'.
2840
 
2841
 -- Function: jstring JvNewStringUTF (const char* BYTES)
2842
     Returns a `String' which is made up of the UTF encoded characters
2843
     present in the C string BYTES.
2844
 
2845
 -- Function: jchar* JvGetStringChars (jstring STR)
2846
     Returns a pointer to an array of characters making up the `String'
2847
     STR.
2848
 
2849
 -- Function: int JvGetStringUTFLength (jstring STR)
2850
     Returns the number of bytes required to encode the contents of the
2851
     `String' STR in UTF-8.
2852
 
2853
 -- Function: jsize JvGetStringUTFRegion (jstring STR, jsize START,
2854
          jsize LEN, char* BUF)
2855
     Puts the UTF-8 encoding of a region of the `String' STR into the
2856
     buffer `buf'.  The region to fetch is marked by START and LEN.
2857
 
2858
     Note that BUF is a buffer, not a C string.  It is _not_ null
2859
     terminated.
2860
 
2861

2862
File: gcj.info,  Node: Mixing with C++,  Next: Exception Handling,  Prev: Strings,  Up: About CNI
2863
 
2864
11.13 Interoperating with C/C++
2865
===============================
2866
 
2867
Because CNI is designed to represent Java classes and methods it cannot
2868
be mixed readily with C/C++ types.
2869
 
2870
   One important restriction is that Java classes cannot have non-Java
2871
type instance or static variables and cannot have methods which take
2872
non-Java types as arguments or return non-Java types.
2873
 
2874
None of the following is possible with CNI:
2875
 
2876
 
2877
     class ::MyClass : public java::lang::Object
2878
     {
2879
        char* variable;  // char* is not a valid Java type.
2880
     }
2881
 
2882
 
2883
     uint
2884
     ::SomeClass::someMethod (char *arg)
2885
     {
2886
       .
2887
       .
2888
       .
2889
     }   // `uint' is not a valid Java type, neither is `char*'
2890
 
2891
Of course, it is ok to use C/C++ types within the scope of a method:
2892
 
2893
     jint
2894
     ::SomeClass::otherMethod (jstring str)
2895
     {
2896
        char *arg = ...
2897
        .
2898
        .
2899
        .
2900
     }
2901
 
2902
11.13.1 RawData
2903
---------------
2904
 
2905
The above restriction can be problematic, so CNI includes the
2906
`gnu.gcj.RawData' class.  The `RawData' class is a "non-scanned
2907
reference" type.  In other words variables declared of type `RawData'
2908
can contain any data and are not checked by the compiler or memory
2909
manager in any way.
2910
 
2911
   This means that you can put C/C++ data structures (including classes)
2912
in your CNI classes, as long as you use the appropriate cast.
2913
 
2914
Here are some examples:
2915
 
2916
 
2917
     class ::MyClass : public java::lang::Object
2918
     {
2919
        gnu.gcj.RawData string;
2920
 
2921
        MyClass ();
2922
        gnu.gcj.RawData getText ();
2923
        void printText ();
2924
     }
2925
 
2926
     ::MyClass::MyClass ()
2927
     {
2928
        char* text = ...
2929
        string = text;
2930
     }
2931
 
2932
     gnu.gcj.RawData
2933
     ::MyClass::getText ()
2934
     {
2935
        return string;
2936
     }
2937
 
2938
     void
2939
     ::MyClass::printText ()
2940
     {
2941
       printf("%s\n", (char*) string);
2942
     }
2943
 
2944
11.13.2 RawDataManaged
2945
----------------------
2946
 
2947
`gnu.gcj.RawDataManaged' is another type used to indicate special data
2948
used by native code. Unlike the `RawData' type, fields declared as
2949
`RawDataManaged' will be "marked" by the memory manager and considered
2950
for garbage collection.
2951
 
2952
   Native data which is allocated using CNI's `JvAllocBytes()' function
2953
and stored in a `RawDataManaged' will be automatically freed when the
2954
Java object it is associated with becomes unreachable.
2955
 
2956
11.13.3 Native memory allocation
2957
--------------------------------
2958
 
2959
 -- Function: void* JvAllocBytes (jsize SIZE)
2960
     Allocates SIZE bytes from the heap.  The memory returned is zeroed.
2961
     This memory is not scanned for pointers by the garbage collector,
2962
     but will be freed if no references to it are discovered.
2963
 
2964
     This function can be useful if you need to associate some native
2965
     data with a Java object. Using a CNI's special `RawDataManaged'
2966
     type, native data allocated with `JvAllocBytes' will be
2967
     automatically freed when the Java object itself becomes
2968
     unreachable.
2969
 
2970
11.13.4 Posix signals
2971
---------------------
2972
 
2973
On Posix based systems the `libgcj' library uses several signals
2974
internally.  CNI code should not attempt to use the same signals as
2975
doing so may cause `libgcj' and/or the CNI code to fail.
2976
 
2977
   SIGSEGV is used on many systems to generate `NullPointerExceptions'.
2978
SIGCHLD is used internally by `Runtime.exec()'.  Several other signals
2979
(that vary from platform to platform) can be used by the memory manager
2980
and by `Thread.interrupt()'.
2981
 
2982

2983
File: gcj.info,  Node: Exception Handling,  Next: Synchronization,  Prev: Mixing with C++,  Up: About CNI
2984
 
2985
11.14 Exception Handling
2986
========================
2987
 
2988
While C++ and Java share a common exception handling framework, things
2989
are not yet perfectly integrated.  The main issue is that the run-time
2990
type information facilities of the two languages are not integrated.
2991
 
2992
   Still, things work fairly well.  You can throw a Java exception from
2993
C++ using the ordinary `throw' construct, and this exception can be
2994
caught by Java code.  Similarly, you can catch an exception thrown from
2995
Java using the C++ `catch' construct.
2996
 
2997
Here is an example:
2998
 
2999
     if (i >= count)
3000
        throw new java::lang::IndexOutOfBoundsException();
3001
 
3002
   Normally, G++ will automatically detect when you are writing C++
3003
code that uses Java exceptions, and handle them appropriately.
3004
However, if C++ code only needs to execute destructors when Java
3005
exceptions are thrown through it, GCC will guess incorrectly.  Sample
3006
problematic code:
3007
 
3008
     struct S { ~S(); };
3009
 
3010
     extern void bar();    // Is implemented in Java and may throw exceptions.
3011
 
3012
     void foo()
3013
     {
3014
       S s;
3015
       bar();
3016
     }
3017
 
3018
   The usual effect of an incorrect guess is a link failure,
3019
complaining of a missing routine called `__gxx_personality_v0'.
3020
 
3021
   You can inform the compiler that Java exceptions are to be used in a
3022
translation unit, irrespective of what it might think, by writing
3023
`#pragma GCC java_exceptions' at the head of the file.  This `#pragma'
3024
must appear before any functions that throw or catch exceptions, or run
3025
destructors when exceptions are thrown through them.
3026
 
3027

3028
File: gcj.info,  Node: Synchronization,  Next: Invocation,  Prev: Exception Handling,  Up: About CNI
3029
 
3030
11.15 Synchronization
3031
=====================
3032
 
3033
Each Java object has an implicit monitor.  The Java VM uses the
3034
instruction `monitorenter' to acquire and lock a monitor, and
3035
`monitorexit' to release it.
3036
 
3037
   The corresponding CNI macros are `JvMonitorEnter' and
3038
`JvMonitorExit' (JNI has similar  methods `MonitorEnter' and
3039
`MonitorExit').
3040
 
3041
   The Java source language does not provide direct access to these
3042
primitives.  Instead, there is a `synchronized' statement that does an
3043
implicit `monitorenter' before entry to the block, and does a
3044
`monitorexit' on exit from the block.  Note that the lock has to be
3045
released even when the block is abnormally terminated by an exception,
3046
which means there is an implicit `try finally' surrounding
3047
synchronization locks.
3048
 
3049
   From C++, it makes sense to use a destructor to release a lock.  CNI
3050
defines the following utility class:
3051
 
3052
     class JvSynchronize() {
3053
       jobject obj;
3054
       JvSynchronize(jobject o) { obj = o; JvMonitorEnter(o); }
3055
       ~JvSynchronize() { JvMonitorExit(obj); }
3056
     };
3057
 
3058
   So this Java code:
3059
 
3060
     synchronized (OBJ)
3061
     {
3062
        CODE
3063
     }
3064
 
3065
might become this C++ code:
3066
 
3067
     {
3068
        JvSynchronize dummy (OBJ);
3069
        CODE;
3070
     }
3071
 
3072
   Java also has methods with the `synchronized' attribute.  This is
3073
equivalent to wrapping the entire method body in a `synchronized'
3074
statement.  (Alternatively, an implementation could require the caller
3075
to do the synchronization.  This is not practical for a compiler,
3076
because each virtual method call would have to test at run-time if
3077
synchronization is needed.)  Since in `gcj' the `synchronized'
3078
attribute is handled by the method implementation, it is up to the
3079
programmer of a synchronized native method to handle the synchronization
3080
(in the C++ implementation of the method).  In other words, you need to
3081
manually add `JvSynchronize' in a `native synchronized' method.
3082
 
3083

3084
File: gcj.info,  Node: Invocation,  Next: Reflection,  Prev: Synchronization,  Up: About CNI
3085
 
3086
11.16 Invocation
3087
================
3088
 
3089
CNI permits C++ applications to make calls into Java classes, in
3090
addition to allowing Java code to call into C++. Several functions,
3091
known as the "invocation API", are provided to support this.
3092
 
3093
 -- Function: jint JvCreateJavaVM (JvVMInitArgs* VM_ARGS)
3094
     Initializes the Java runtime. This function performs essential
3095
     initialization of the threads interface, garbage collector,
3096
     exception handling and other key aspects of the runtime. It must
3097
     be called once by an application with a non-Java `main()'
3098
     function, before any other Java or CNI calls are made.  It is
3099
     safe, but not recommended, to call `JvCreateJavaVM()' more than
3100
     once provided it is only called from a single thread.  The VMARGS
3101
     parameter can be used to specify initialization parameters for the
3102
     Java runtime. It may be `NULL'.
3103
 
3104
     JvVMInitArgs represents a list of virtual machine initialization
3105
     arguments. `JvCreateJavaVM()' ignores the version field.
3106
 
3107
          typedef struct JvVMOption
3108
          {
3109
            // a VM initialization option
3110
            char* optionString;
3111
            // extra information associated with this option
3112
            void* extraInfo;
3113
          } JvVMOption;
3114
 
3115
          typedef struct JvVMInitArgs
3116
          {
3117
            // for compatibility with JavaVMInitArgs
3118
            jint version;
3119
 
3120
            // number of VM initialization options
3121
            jint nOptions;
3122
 
3123
            // an array of VM initialization options
3124
            JvVMOption* options;
3125
 
3126
            // true if the option parser should ignore unrecognized options
3127
            jboolean ignoreUnrecognized;
3128
          } JvVMInitArgs;
3129
 
3130
     `JvCreateJavaVM()' returns `0' upon success, or `-1' if the
3131
     runtime is already initialized.
3132
 
3133
     _Note:_ In GCJ 3.1, the `vm_args' parameter is ignored. It is
3134
     recognized and used as of release 4.0.
3135
 
3136
 -- Function: java::lang::Thread* JvAttachCurrentThread (jstring NAME,
3137
          java::lang::ThreadGroup* GROUP)
3138
     Registers an existing thread with the Java runtime.  This must be
3139
     called once from each thread, before that thread makes any other
3140
     Java or CNI calls. It must be called after `JvCreateJavaVM'.  NAME
3141
     specifies a name for the thread. It may be `NULL', in which case a
3142
     name will be generated.  GROUP is the ThreadGroup in which this
3143
     thread will be a member. If it is `NULL', the thread will be a
3144
     member of the main thread group.  The return value is the Java
3145
     `Thread' object that represents the thread.  It is safe to call
3146
     `JvAttachCurrentThread()' more than once from the same thread. If
3147
     the thread is already attached, the call is ignored and the current
3148
     thread object is returned.
3149
 
3150
 -- Function: jint JvDetachCurrentThread ()
3151
     Unregisters a thread from the Java runtime. This should be called
3152
     by threads that were attached using `JvAttachCurrentThread()',
3153
     after they have finished making calls to Java code. This ensures
3154
     that any resources associated with the thread become eligible for
3155
     garbage collection.  This function returns `0' upon success, or
3156
     `-1' if the current thread is not attached.
3157
 
3158
11.16.1 Handling uncaught exceptions
3159
------------------------------------
3160
 
3161
If an exception is thrown from Java code called using the invocation
3162
API, and no handler for the exception can be found, the runtime will
3163
abort the application. In order to make the application more robust, it
3164
is recommended that code which uses the invocation API be wrapped by a
3165
top-level try/catch block that catches all Java exceptions.
3166
 
3167
11.16.2 Example
3168
---------------
3169
 
3170
The following code demonstrates the use of the invocation API. In this
3171
example, the C++ application initializes the Java runtime and attaches
3172
itself. The `java.lang.System' class is initialized in order to access
3173
its `out' field, and a Java string is printed. Finally, the thread is
3174
detached from the runtime once it has finished making Java calls.
3175
Everything is wrapped with a try/catch block to provide a default
3176
handler for any uncaught exceptions.
3177
 
3178
   The example can be compiled with `c++ -c test.cc; gcj test.o'.
3179
 
3180
     // test.cc
3181
     #include 
3182
     #include 
3183
     #include 
3184
     #include 
3185
 
3186
     int main(int argc, char *argv[])
3187
     {
3188
       using namespace java::lang;
3189
 
3190
       try
3191
       {
3192
         JvCreateJavaVM(NULL);
3193
         JvAttachCurrentThread(NULL, NULL);
3194
 
3195
         String *message = JvNewStringLatin1("Hello from C++");
3196
         JvInitClass(&System::class$);
3197
         System::out->println(message);
3198
 
3199
         JvDetachCurrentThread();
3200
       }
3201
       catch (Throwable *t)
3202
       {
3203
         System::err->println(JvNewStringLatin1("Unhandled Java exception:"));
3204
         t->printStackTrace();
3205
       }
3206
     }
3207
 
3208

3209
File: gcj.info,  Node: Reflection,  Prev: Invocation,  Up: About CNI
3210
 
3211
11.17 Reflection
3212
================
3213
 
3214
Reflection is possible with CNI code, it functions similarly to how it
3215
functions with JNI.
3216
 
3217
   The types `jfieldID' and `jmethodID' are as in JNI.
3218
 
3219
The functions:
3220
 
3221
   * `JvFromReflectedField',
3222
 
3223
   * `JvFromReflectedMethod',
3224
 
3225
   * `JvToReflectedField'
3226
 
3227
   * `JvToFromReflectedMethod'
3228
 
3229
will be added shortly, as will other functions corresponding to JNI.
3230
 
3231

3232
File: gcj.info,  Node: System properties,  Next: Resources,  Prev: About CNI,  Up: Top
3233
 
3234
12 System properties
3235
********************
3236
 
3237
The runtime behavior of the `libgcj' library can be modified by setting
3238
certain system properties.  These properties can be compiled into the
3239
program using the `-DNAME[=VALUE]' option to `gcj' or by setting them
3240
explicitly in the program by calling the
3241
`java.lang.System.setProperty()' method.  Some system properties are
3242
only used for informational purposes (like giving a version number or a
3243
user name).  A program can inspect the current value of a property by
3244
calling the `java.lang.System.getProperty()' method.
3245
 
3246
* Menu:
3247
 
3248
* Standard Properties::         Standard properties supported by `libgcj'
3249
* GNU Classpath Properties::    Properties found in Classpath based libraries
3250
* libgcj Runtime Properties::   Properties specific to `libgcj'
3251
 
3252

3253
File: gcj.info,  Node: Standard Properties,  Next: GNU Classpath Properties,  Up: System properties
3254
 
3255
12.1 Standard Properties
3256
========================
3257
 
3258
The following properties are normally found in all implementations of
3259
the core libraries for the Java language.
3260
 
3261
`java.version'
3262
     The `libgcj' version number.
3263
 
3264
`java.vendor'
3265
     Set to `The Free Software Foundation, Inc.'
3266
 
3267
`java.vendor.url'
3268
     Set to `http://gcc.gnu.org/java/'.
3269
 
3270
`java.home'
3271
     The directory where `gcj' was installed.  Taken from the `--prefix'
3272
     option given to `configure'.
3273
 
3274
`java.class.version'
3275
     The class format version number supported by the libgcj byte code
3276
     interpreter.  (Currently `46.0')
3277
 
3278
`java.vm.specification.version'
3279
     The Virtual Machine Specification version implemented by `libgcj'.
3280
     (Currently `1.0')
3281
 
3282
`java.vm.specification.vendor'
3283
     The name of the Virtual Machine specification designer.
3284
 
3285
`java.vm.specification.name'
3286
     The name of the Virtual Machine specification (Set to `Java
3287
     Virtual Machine Specification').
3288
 
3289
`java.vm.version'
3290
     The `gcj' version number.
3291
 
3292
`java.vm.vendor'
3293
     Set to `The Free Software Foundation, Inc.'
3294
 
3295
`java.vm.name'
3296
     Set to `GNU libgcj'.
3297
 
3298
`java.specification.version'
3299
     The Runtime Environment specification version implemented by
3300
     `libgcj'.  (Currently set to `1.3')
3301
 
3302
`java.specification.vendor'
3303
     The Runtime Environment specification designer.
3304
 
3305
`java.specification.name'
3306
     The name of the Runtime Environment specification (Set to `Java
3307
     Platform API Specification').
3308
 
3309
`java.class.path'
3310
     The paths (jar files, zip files and directories) used for finding
3311
     class files.
3312
 
3313
`java.library.path'
3314
     Directory path used for finding native libraries.
3315
 
3316
`java.io.tmpdir'
3317
     The directory used to put temporary files in.
3318
 
3319
`java.compiler'
3320
     Name of the Just In Time compiler to use by the byte code
3321
     interpreter.  Currently not used in `libgcj'.
3322
 
3323
`java.ext.dirs'
3324
     Directories containing jar files with extra libraries.  Will be
3325
     used when resolving classes.
3326
 
3327
`java.protocol.handler.pkgs'
3328
     A `|' separated list of package names that is used to find classes
3329
     that implement handlers for `java.net.URL'.
3330
 
3331
`java.rmi.server.codebase'
3332
     A list of URLs that is used by the `java.rmi.server.RMIClassLoader'
3333
     to load classes from.
3334
 
3335
`jdbc.drivers'
3336
     A list of class names that will be loaded by the
3337
     `java.sql.DriverManager' when it starts up.
3338
 
3339
`file.separator'
3340
     The separator used in when directories are included in a filename
3341
     (normally `/' or `\' ).
3342
 
3343
`file.encoding'
3344
     The default character encoding used when converting platform
3345
     native files to Unicode (usually set to `8859_1').
3346
 
3347
`path.separator'
3348
     The standard separator used when a string contains multiple paths
3349
     (normally `:' or `;'), the string is usually not a valid character
3350
     to use in normal directory names.)
3351
 
3352
`line.separator'
3353
     The default line separator used on the platform (normally `\n',
3354
     `\r' or a combination of those two characters).
3355
 
3356
`policy.provider'
3357
     The class name used for the default policy provider returned by
3358
     `java.security.Policy.getPolicy'.
3359
 
3360
`user.name'
3361
     The name of the user running the program.  Can be the full name,
3362
     the login name or empty if unknown.
3363
 
3364
`user.home'
3365
     The default directory to put user specific files in.
3366
 
3367
`user.dir'
3368
     The current working directory from which the program was started.
3369
 
3370
`user.language'
3371
     The default language as used by the `java.util.Locale' class.
3372
 
3373
`user.region'
3374
     The default region as used by the `java.util.Local' class.
3375
 
3376
`user.variant'
3377
     The default variant of the language and region local used.
3378
 
3379
`user.timezone'
3380
     The default timezone as used by the `java.util.TimeZone' class.
3381
 
3382
`os.name'
3383
     The operating system/kernel name that the program runs on.
3384
 
3385
`os.arch'
3386
     The hardware that we are running on.
3387
 
3388
`os.version'
3389
     The version number of the operating system/kernel.
3390
 
3391
`awt.appletWarning'
3392
     The string to display when an untrusted applet is displayed.
3393
     Returned by `java.awt.Window.getWarningString()' when the window is
3394
     "insecure".
3395
 
3396
`awt.toolkit'
3397
     The class name used for initializing the default
3398
     `java.awt.Toolkit'.  Defaults to `gnu.awt.gtk.GtkToolkit'.
3399
 
3400
`http.proxyHost'
3401
     Name of proxy host for http connections.
3402
 
3403
`http.proxyPort'
3404
     Port number to use when a proxy host is in use.
3405
 
3406
 
3407

3408
File: gcj.info,  Node: GNU Classpath Properties,  Next: libgcj Runtime Properties,  Prev: Standard Properties,  Up: System properties
3409
 
3410
12.2 GNU Classpath Properties
3411
=============================
3412
 
3413
`libgcj' is based on the GNU Classpath (Essential Libraries for Java) a
3414
GNU project to create free core class libraries for use with virtual
3415
machines and compilers for the Java language.  The following properties
3416
are common to libraries based on GNU Classpath.
3417
 
3418
`gcj.dumpobject'
3419
     Enables printing serialization debugging by the
3420
     `java.io.ObjectInput' and `java.io.ObjectOutput' classes when set
3421
     to something else then the empty string.  Only used when running a
3422
     debug build of the library.
3423
 
3424
`gnu.classpath.vm.shortname'
3425
     This is a succinct name of the virtual machine.  For `libgcj',
3426
     this will always be `libgcj'.
3427
 
3428
`gnu.classpath.home.url'
3429
     A base URL used for finding system property files (e.g.,
3430
     `classpath.security').  By default this is a `file:' URL pointing
3431
     to the `lib' directory under `java.home'.
3432
 
3433
 
3434

3435
File: gcj.info,  Node: libgcj Runtime Properties,  Prev: GNU Classpath Properties,  Up: System properties
3436
 
3437
12.3 libgcj Runtime Properties
3438
==============================
3439
 
3440
The following properties are specific to the `libgcj' runtime and will
3441
normally not be found in other core libraries for the java language.
3442
 
3443
`java.fullversion'
3444
     The combination of `java.vm.name' and `java.vm.version'.
3445
 
3446
`java.vm.info'
3447
     Same as `java.fullversion'.
3448
 
3449
`impl.prefix'
3450
     Used by the `java.net.DatagramSocket' class when set to something
3451
     else then the empty string.  When set all newly created
3452
     `DatagramSocket's will try to load a class
3453
     `java.net.[impl.prefix]DatagramSocketImpl' instead of the normal
3454
     `java.net.PlainDatagramSocketImpl'.
3455
 
3456
`gnu.gcj.progname'
3457
     The class or binary name that was used to invoke the program. This
3458
     will be the name of the "main" class in the case where the `gij'
3459
     front end is used, or the program binary name in the case where an
3460
     application is compiled to a native binary.
3461
 
3462
`gnu.gcj.user.realname'
3463
     The real name of the user, as taken from the password file.  This
3464
     may not always hold only the user's name (as some sites put extra
3465
     information in this field).  Also, this property is not available
3466
     on all platforms.
3467
 
3468
`gnu.gcj.runtime.NameFinder.use_addr2line'
3469
     Whether an external process, `addr2line', should be used to
3470
     determine line number information when tracing the stack. Setting
3471
     this to `false' may suppress line numbers when printing stack
3472
     traces and when using the java.util.logging infrastructure.
3473
     However, performance may improve significantly for applications
3474
     that print stack traces or make logging calls frequently.
3475
 
3476
`gnu.gcj.runtime.NameFinder.show_raw'
3477
     Whether the address of a stack frame should be printed when the
3478
     line number is unavailable. Setting this to `true' will cause the
3479
     name of the object and the offset within that object to be printed
3480
     when no line number is available.  This allows for off-line
3481
     decoding of stack traces if necessary debug information is
3482
     available.  The default is `false', no raw addresses are printed.
3483
 
3484
`gnu.gcj.runtime.NameFinder.remove_unknown'
3485
     Whether stack frames for non-java code should be included in a
3486
     stack trace.  The default value is `true', stack frames for
3487
     non-java code are suppressed.  Setting this to `false' will cause
3488
     any non-java stack frames to be printed in addition to frames for
3489
     the java code.
3490
 
3491
`gnu.gcj.runtime.VMClassLoader.library_control'
3492
     This controls how shared libraries are automatically loaded by the
3493
     built-in class loader.  If this property is set to `full', a full
3494
     search is done for each requested class.  If this property is set
3495
     to `cache', then any failed lookups are cached and not tried again.
3496
     If this property is set to `never' (the default), then lookups are
3497
     never done.  For more information, *Note Extensions::.
3498
 
3499
`gnu.gcj.runtime.endorsed.dirs'
3500
     This is like the standard `java.endorsed.dirs', property, but
3501
     specifies some extra directories which are searched after the
3502
     standard endorsed directories.  This is primarily useful for
3503
     telling `libgcj' about additional libraries which are ordinarily
3504
     incorporated into the JDK, and which should be loaded by the
3505
     bootstrap class loader, but which are not yet part of `libgcj'
3506
     itself for some reason.
3507
 
3508
`gnu.gcj.jit.compiler'
3509
     This is the full path to `gcj' executable which should be used to
3510
     compile classes just-in-time when `ClassLoader.defineClass' is
3511
     called.  If not set, `gcj' will not be invoked by the runtime;
3512
     this can also be controlled via `Compiler.disable'.
3513
 
3514
`gnu.gcj.jit.options'
3515
     This is a space-separated string of options which should be passed
3516
     to `gcj' when in JIT mode.  If not set, a sensible default is
3517
     chosen.
3518
 
3519
`gnu.gcj.jit.cachedir'
3520
     This is the directory where cached shared library files are
3521
     stored.  If not set, JIT compilation is disabled.  This should
3522
     never be set to a directory that is writable by any other user.
3523
 
3524
`gnu.gcj.precompiled.db.path'
3525
     This is a sequence of file names, each referring to a file created
3526
     by `gcj-dbtool'.  These files will be used by `libgcj' to find
3527
     shared libraries corresponding to classes that are loaded from
3528
     bytecode.  `libgcj' often has a built-in default database; it can
3529
     be queried using `gcj-dbtool -p'.
3530
 
3531
 
3532

3533
File: gcj.info,  Node: Resources,  Next: Index,  Prev: System properties,  Up: Top
3534
 
3535
13 Resources
3536
************
3537
 
3538
While writing `gcj' and `libgcj' we have, of course, relied heavily on
3539
documentation from Sun Microsystems.  In particular we have used The
3540
Java Language Specification (both first and second editions), the Java
3541
Class Libraries (volumes one and two), and the Java Virtual Machine
3542
Specification.  In addition we've used the online documentation at
3543
`http://java.sun.com/'.
3544
 
3545
   The current `gcj' home page is `http://gcc.gnu.org/java/'.
3546
 
3547
   For more information on gcc, see `http://gcc.gnu.org/'.
3548
 
3549
   Some `libgcj' testing is done using the Mauve test suite.  This is a
3550
free software Java class library test suite which is being written
3551
because the JCK is not free.  See `http://sources.redhat.com/mauve/'
3552
for more information.
3553
 
3554

3555
File: gcj.info,  Node: Index,  Prev: Resources,  Up: Top
3556
 
3557
Index
3558
*****
3559
 
3560
 
3561
* Menu:
3562
3563
* class path:                            Input Options.        (line  6)
3564
* class$:                                Reference types.      (line 20)
3565
* elements on template:         Arrays.               (line 46)
3566
* FDL, GNU Free Documentation License:   GNU Free Documentation License.
3567
                                                               (line  6)
3568
* GCJ_PROPERTIES:                        Extensions.           (line 56)
3569
* jclass:                                Reference types.      (line 16)
3570
* jobject:                               Reference types.      (line 16)
3571
* jstring:                               Reference types.      (line 16)
3572
* JvAllocBytes:                          Mixing with C++.      (line 99)
3573
* JvAttachCurrentThread:                 Invocation.           (line 55)
3574
* JvCreateJavaVM:                        Invocation.           (line 11)
3575
* JvDetachCurrentThread:                 Invocation.           (line 68)
3576
* JvFree:                                Memory allocation.    (line 19)
3577
* JvGetArrayLength:                      Arrays.               (line 86)
3578
* JvGetStringChars:                      Strings.              (line 25)
3579
* JvGetStringUTFLength:                  Strings.              (line 29)
3580
* JvGetStringUTFRegion:                  Strings.              (line 34)
3581
* JvMalloc:                              Memory allocation.    (line 11)
3582
* JvNewBooleanArray:                     Arrays.               (line 83)
3583
* JvNewObjectArray:                      Arrays.               (line 57)
3584
* JvNewString:                           Strings.              (line 11)
3585
* JvNewStringLatin1:                     Strings.              (line 15)
3586
 
3587
 
3588
* JvRealloc:                             Memory allocation.    (line 15)
3589
3590
3591

3592
Tag Table:
3593
Node: Top2803
3594
Node: Copying4222
3595
Node: GNU Free Documentation License41772
3596
Node: Invoking gcj64184
3597
Node: Input and output files64947
3598
Node: Input Options66473
3599
Node: Encodings69747
3600
Node: Warnings70953
3601
Node: Linking72066
3602
Node: Code Generation75005
3603
Node: Configure-time Options81785
3604
Node: Compatibility83525
3605
Node: Limitations84009
3606
Node: Extensions85591
3607
Node: Invoking jcf-dump88685
3608
Node: Invoking gij89630
3609
Node: Invoking gcj-dbtool92881
3610
Node: Invoking jv-convert95347
3611
Node: Invoking grmic96426
3612
Node: Invoking gc-analyze97812
3613
Node: Invoking aot-compile99253
3614
Node: Invoking rebuild-gcj-db100202
3615
Node: About CNI100512
3616
Node: Basic concepts101971
3617
Node: Packages104867
3618
Node: Primitive types107195
3619
Node: Reference types108873
3620
Node: Interfaces109962
3621
Node: Objects and Classes110873
3622
Node: Class Initialization113068
3623
Node: Object allocation115410
3624
Node: Memory allocation116200
3625
Node: Arrays116832
3626
Node: Methods119642
3627
Node: Strings122463
3628
Node: Mixing with C++123967
3629
Node: Exception Handling127438
3630
Node: Synchronization129072
3631
Node: Invocation131062
3632
Node: Reflection135998
3633
Node: System properties136459
3634
Node: Standard Properties137336
3635
Node: GNU Classpath Properties141768
3636
Node: libgcj Runtime Properties142815
3637
Node: Resources147317

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