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1 284 jeremybenn
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.rm #[ #] #H #V #F C
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.\" ========================================================================
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.\"
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.IX Title "GCJ 1"
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.TH GCJ 1 "2010-07-31" "gcc-4.5.1" "GNU"
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.\" For nroff, turn off justification.  Always turn off hyphenation; it makes
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.\" way too many mistakes in technical documents.
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.if n .ad l
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.nh
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.SH "NAME"
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gcj \- Ahead\-of\-time compiler for the Java language
142
.SH "SYNOPSIS"
143
.IX Header "SYNOPSIS"
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gcj [\fB\-I\fR\fIdir\fR...] [\fB\-d\fR \fIdir\fR...]
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    [\fB\-\-CLASSPATH\fR=\fIpath\fR] [\fB\-\-classpath\fR=\fIpath\fR]
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    [\fB\-f\fR\fIoption\fR...] [\fB\-\-encoding\fR=\fIname\fR]
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    [\fB\-\-main\fR=\fIclassname\fR] [\fB\-D\fR\fIname\fR[=\fIvalue\fR]...]
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    [\fB\-C\fR] [\fB\-\-resource\fR \fIresource-name\fR] [\fB\-d\fR \fIdirectory\fR]
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    [\fB\-W\fR\fIwarn\fR...]
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    \fIsourcefile\fR...
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.SH "DESCRIPTION"
152
.IX Header "DESCRIPTION"
153
As \fBgcj\fR is just another front end to \fBgcc\fR, it supports many
154
of the same options as gcc.    This manual only documents the
155
options specific to \fBgcj\fR.
156
.SH "OPTIONS"
157
.IX Header "OPTIONS"
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.Sh "Input and output files"
159
.IX Subsection "Input and output files"
160
A \fBgcj\fR command is like a \fBgcc\fR command, in that it
161
consists of a number of options and file names.  The following kinds
162
of input file names are supported:
163
.IP "\fIfile\fR\fB.java\fR" 4
164
.IX Item "file.java"
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Java source files.
166
.IP "\fIfile\fR\fB.class\fR" 4
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.IX Item "file.class"
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Java bytecode files.
169
.IP "\fIfile\fR\fB.zip\fR" 4
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.IX Item "file.zip"
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.PD 0
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.IP "\fIfile\fR\fB.jar\fR" 4
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.IX Item "file.jar"
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.PD
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An archive containing one or more \f(CW\*(C`.class\*(C'\fR files, all of
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which are compiled.  The archive may be compressed.  Files in
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an archive which don't end with \fB.class\fR are treated as
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resource files; they are compiled into the resulting object file
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as \fBcore:\fR URLs.
180
.IP "\fB@\fR\fIfile\fR" 4
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.IX Item "@file"
182
A file containing a whitespace-separated list of input file names.
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(Currently, these must all be \f(CW\*(C`.java\*(C'\fR source files, but that
184
may change.)
185
Each named file is compiled, just as if it had been on the command line.
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.IP "\fIlibrary\fR\fB.a\fR" 4
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.IX Item "library.a"
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.PD 0
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.IP "\fIlibrary\fR\fB.so\fR" 4
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.IX Item "library.so"
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.IP "\fB\-l\fR\fIlibname\fR" 4
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.IX Item "-llibname"
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.PD
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Libraries to use when linking.  See the \fBgcc\fR manual.
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.PP
196
You can specify more than one input file on the \fBgcj\fR command line,
197
in which case they will all be compiled.  If you specify a
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\&\f(CW\*(C`\-o \f(CIFILENAME\f(CW\*(C'\fR
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option, all the input files will be compiled together, producing a
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single output file, named \fI\s-1FILENAME\s0\fR.
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This is allowed even when using \f(CW\*(C`\-S\*(C'\fR or \f(CW\*(C`\-c\*(C'\fR,
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but not when using \f(CW\*(C`\-C\*(C'\fR or \f(CW\*(C`\-\-resource\*(C'\fR.
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(This is an extension beyond the what plain \fBgcc\fR allows.)
204
(If more than one input file is specified, all must currently
205
be \f(CW\*(C`.java\*(C'\fR files, though we hope to fix this.)
206
.Sh "Input Options"
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.IX Subsection "Input Options"
208
\&\fBgcj\fR has options to control where it looks to find files it needs.
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For instance, \fBgcj\fR might need to load a class that is referenced
210
by the file it has been asked to compile.  Like other compilers for the
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Java language, \fBgcj\fR has a notion of a \fIclass path\fR.  There are
212
several options and environment variables which can be used to
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manipulate the class path.  When \fBgcj\fR looks for a given class, it
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searches the class path looking for matching \fI.class\fR or
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\&\fI.java\fR file.  \fBgcj\fR comes with a built-in class path which
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points at the installed \fIlibgcj.jar\fR, a file which contains all the
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standard classes.
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.PP
219
In the text below, a directory or path component can refer either to an
220
actual directory on the filesystem, or to a \fI.zip\fR or \fI.jar\fR
221
file, which \fBgcj\fR will search as if it is a directory.
222
.IP "\fB\-I\fR\fIdir\fR" 4
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.IX Item "-Idir"
224
All directories specified by \f(CW\*(C`\-I\*(C'\fR are kept in order and prepended
225
to the class path constructed from all the other options.  Unless
226
compatibility with tools like \f(CW\*(C`javac\*(C'\fR is important, we recommend
227
always using \f(CW\*(C`\-I\*(C'\fR instead of the other options for manipulating the
228
class path.
229
.IP "\fB\-\-classpath=\fR\fIpath\fR" 4
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.IX Item "--classpath=path"
231
This sets the class path to \fIpath\fR, a colon-separated list of paths
232
(on Windows-based systems, a semicolon-separate list of paths).
233
This does not override the builtin (\*(L"boot\*(R") search path.
234
.IP "\fB\-\-CLASSPATH=\fR\fIpath\fR" 4
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.IX Item "--CLASSPATH=path"
236
Deprecated synonym for \f(CW\*(C`\-\-classpath\*(C'\fR.
237
.IP "\fB\-\-bootclasspath=\fR\fIpath\fR" 4
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.IX Item "--bootclasspath=path"
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Where to find the standard builtin classes, such as \f(CW\*(C`java.lang.String\*(C'\fR.
240
.IP "\fB\-\-extdirs=\fR\fIpath\fR" 4
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.IX Item "--extdirs=path"
242
For each directory in the \fIpath\fR, place the contents of that
243
directory at the end of the class path.
244
.IP "\fB\s-1CLASSPATH\s0\fR" 4
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.IX Item "CLASSPATH"
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This is an environment variable which holds a list of paths.
247
.PP
248
The final class path is constructed like so:
249
.IP "\(bu" 4
250
First come all directories specified via \f(CW\*(C`\-I\*(C'\fR.
251
.IP "\(bu" 4
252
If \fB\-\-classpath\fR is specified, its value is appended.
253
Otherwise, if the \f(CW\*(C`CLASSPATH\*(C'\fR environment variable is specified,
254
then its value is appended.
255
Otherwise, the current directory (\f(CW"."\fR) is appended.
256
.IP "\(bu" 4
257
If \f(CW\*(C`\-\-bootclasspath\*(C'\fR was specified, append its value.
258
Otherwise, append the built-in system directory, \fIlibgcj.jar\fR.
259
.IP "\(bu" 4
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Finally, if \f(CW\*(C`\-\-extdirs\*(C'\fR was specified, append the contents of the
261
specified directories at the end of the class path.  Otherwise, append
262
the contents of the built-in extdirs at \f(CW\*(C`$(prefix)/share/java/ext\*(C'\fR.
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.PP
264
The classfile built by \fBgcj\fR for the class \f(CW\*(C`java.lang.Object\*(C'\fR
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(and placed in \f(CW\*(C`libgcj.jar\*(C'\fR) contains a special zero length
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attribute \f(CW\*(C`gnu.gcj.gcj\-compiled\*(C'\fR. The compiler looks for this
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attribute when loading \f(CW\*(C`java.lang.Object\*(C'\fR and will report an error
268
if it isn't found, unless it compiles to bytecode (the option
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\&\f(CW\*(C`\-fforce\-classes\-archive\-check\*(C'\fR can be used to override this
270
behavior in this particular case.)
271
.IP "\fB\-fforce\-classes\-archive\-check\fR" 4
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.IX Item "-fforce-classes-archive-check"
273
This forces the compiler to always check for the special zero length
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attribute \f(CW\*(C`gnu.gcj.gcj\-compiled\*(C'\fR in \f(CW\*(C`java.lang.Object\*(C'\fR and
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issue an error if it isn't found.
276
.IP "\fB\-fsource=\fR\fI\s-1VERSION\s0\fR" 4
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.IX Item "-fsource=VERSION"
278
This option is used to choose the source version accepted by
279
\&\fBgcj\fR.  The default is \fB1.5\fR.
280
.Sh "Encodings"
281
.IX Subsection "Encodings"
282
The Java programming language uses Unicode throughout.  In an effort to
283
integrate well with other locales, \fBgcj\fR allows \fI.java\fR files
284
to be written using almost any encoding.  \fBgcj\fR knows how to
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convert these encodings into its internal encoding at compile time.
286
.PP
287
You can use the \f(CW\*(C`\-\-encoding=\f(CINAME\f(CW\*(C'\fR option to specify an
288
encoding (of a particular character set) to use for source files.  If
289
this is not specified, the default encoding comes from your current
290
locale.  If your host system has insufficient locale support, then
291
\&\fBgcj\fR assumes the default encoding to be the \fB\s-1UTF\-8\s0\fR encoding
292
of Unicode.
293
.PP
294
To implement \f(CW\*(C`\-\-encoding\*(C'\fR, \fBgcj\fR simply uses the host
295
platform's \f(CW\*(C`iconv\*(C'\fR conversion routine.  This means that in practice
296
\&\fBgcj\fR is limited by the capabilities of the host platform.
297
.PP
298
The names allowed for the argument \f(CW\*(C`\-\-encoding\*(C'\fR vary from platform
299
to platform (since they are not standardized anywhere).  However,
300
\&\fBgcj\fR implements the encoding named \fB\s-1UTF\-8\s0\fR internally, so if
301
you choose to use this for your source files you can be assured that it
302
will work on every host.
303
.Sh "Warnings"
304
.IX Subsection "Warnings"
305
\&\fBgcj\fR implements several warnings.  As with other generic
306
\&\fBgcc\fR warnings, if an option of the form \f(CW\*(C`\-Wfoo\*(C'\fR enables a
307
warning, then \f(CW\*(C`\-Wno\-foo\*(C'\fR will disable it.  Here we've chosen to
308
document the form of the warning which will have an effect \*(-- the
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default being the opposite of what is listed.
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.IP "\fB\-Wredundant\-modifiers\fR" 4
311
.IX Item "-Wredundant-modifiers"
312
With this flag, \fBgcj\fR will warn about redundant modifiers.  For
313
instance, it will warn if an interface method is declared \f(CW\*(C`public\*(C'\fR.
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.IP "\fB\-Wextraneous\-semicolon\fR" 4
315
.IX Item "-Wextraneous-semicolon"
316
This causes \fBgcj\fR to warn about empty statements.  Empty statements
317
have been deprecated.
318
.IP "\fB\-Wno\-out\-of\-date\fR" 4
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.IX Item "-Wno-out-of-date"
320
This option will cause \fBgcj\fR not to warn when a source file is
321
newer than its matching class file.  By default \fBgcj\fR will warn
322
about this.
323
.IP "\fB\-Wno\-deprecated\fR" 4
324
.IX Item "-Wno-deprecated"
325
Warn if a deprecated class, method, or field is referred to.
326
.IP "\fB\-Wunused\fR" 4
327
.IX Item "-Wunused"
328
This is the same as \fBgcc\fR's \f(CW\*(C`\-Wunused\*(C'\fR.
329
.IP "\fB\-Wall\fR" 4
330
.IX Item "-Wall"
331
This is the same as \f(CW\*(C`\-Wredundant\-modifiers \-Wextraneous\-semicolon
332
\&\-Wunused\*(C'\fR.
333
.Sh "Linking"
334
.IX Subsection "Linking"
335
To turn a Java application into an executable program,
336
you need to link it with the needed libraries, just as for C or \*(C+.
337
The linker by default looks for a global function named \f(CW\*(C`main\*(C'\fR.
338
Since Java does not have global functions, and a
339
collection of Java classes may have more than one class with a
340
\&\f(CW\*(C`main\*(C'\fR method, you need to let the linker know which of those
341
\&\f(CW\*(C`main\*(C'\fR methods it should invoke when starting the application.
342
You can do that in any of these ways:
343
.IP "\(bu" 4
344
Specify the class containing the desired \f(CW\*(C`main\*(C'\fR method
345
when you link the application, using the \f(CW\*(C`\-\-main\*(C'\fR flag,
346
described below.
347
.IP "\(bu" 4
348
Link the Java package(s) into a shared library (dll) rather than an
349
executable.  Then invoke the application using the \f(CW\*(C`gij\*(C'\fR program,
350
making sure that \f(CW\*(C`gij\*(C'\fR can find the libraries it needs.
351
.IP "\(bu" 4
352
Link the Java packages(s) with the flag \f(CW\*(C`\-lgij\*(C'\fR, which links
353
in the \f(CW\*(C`main\*(C'\fR routine from the \f(CW\*(C`gij\*(C'\fR command.
354
This allows you to select the class whose \f(CW\*(C`main\*(C'\fR method you
355
want to run when you run the application.  You can also use
356
other \f(CW\*(C`gij\*(C'\fR flags, such as \f(CW\*(C`\-D\*(C'\fR flags to set properties.
357
Using the \f(CW\*(C`\-lgij\*(C'\fR library (rather than the \f(CW\*(C`gij\*(C'\fR program
358
of the previous mechanism) has some advantages: it is compatible with
359
static linking, and does not require configuring or installing libraries.
360
.PP
361
These \f(CW\*(C`gij\*(C'\fR options relate to linking an executable:
362
.IP "\fB\-\-main=\fR\fI\s-1CLASSNAME\s0\fR" 4
363
.IX Item "--main=CLASSNAME"
364
This option is used when linking to specify the name of the class whose
365
\&\f(CW\*(C`main\*(C'\fR method should be invoked when the resulting executable is
366
run.
367
.IP "\fB\-D\fR\fIname\fR\fB[=\fR\fIvalue\fR\fB]\fR" 4
368
.IX Item "-Dname[=value]"
369
This option can only be used with \f(CW\*(C`\-\-main\*(C'\fR.  It defines a system
370
property named \fIname\fR with value \fIvalue\fR.  If \fIvalue\fR is not
371
specified then it defaults to the empty string.  These system properties
372
are initialized at the program's startup and can be retrieved at runtime
373
using the \f(CW\*(C`java.lang.System.getProperty\*(C'\fR method.
374
.IP "\fB\-lgij\fR" 4
375
.IX Item "-lgij"
376
Create an application whose command-line processing is that
377
of the \f(CW\*(C`gij\*(C'\fR command.
378
.Sp
379
This option is an alternative to using \f(CW\*(C`\-\-main\*(C'\fR; you cannot use both.
380
.IP "\fB\-static\-libgcj\fR" 4
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.IX Item "-static-libgcj"
382
This option causes linking to be done against a static version of the
383
libgcj runtime library.  This option is only available if
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corresponding linker support exists.
385
.Sp
386
\&\fBCaution:\fR Static linking of libgcj may cause essential parts
387
of libgcj to be omitted.  Some parts of libgcj use reflection to load
388
classes at runtime.  Since the linker does not see these references at
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link time, it can omit the referred to classes.  The result is usually
390
(but not always) a \f(CW\*(C`ClassNotFoundException\*(C'\fR being thrown at
391
runtime. Caution must be used when using this option.  For more
392
details see:
393
<\fBhttp://gcc.gnu.org/wiki/Statically%20linking%20libgcj\fR>
394
.Sh "Code Generation"
395
.IX Subsection "Code Generation"
396
In addition to the many \fBgcc\fR options controlling code generation,
397
\&\fBgcj\fR has several options specific to itself.
398
.IP "\fB\-C\fR" 4
399
.IX Item "-C"
400
This option is used to tell \fBgcj\fR to generate bytecode
401
(\fI.class\fR files) rather than object code.
402
.IP "\fB\-\-resource\fR \fIresource-name\fR" 4
403
.IX Item "--resource resource-name"
404
This option is used to tell \fBgcj\fR to compile the contents of a
405
given file to object code so it may be accessed at runtime with the core
406
protocol handler as \fBcore:/\fR\fIresource-name\fR.  Note that
407
\&\fIresource-name\fR is the name of the resource as found at runtime; for
408
instance, it could be used in a call to \f(CW\*(C`ResourceBundle.getBundle\*(C'\fR.
409
The actual file name to be compiled this way must be specified
410
separately.
411
.IP "\fB\-ftarget=\fR\fI\s-1VERSION\s0\fR" 4
412
.IX Item "-ftarget=VERSION"
413
This can be used with \fB\-C\fR to choose the version of bytecode
414
emitted by \fBgcj\fR.  The default is \fB1.5\fR.  When not
415
generating bytecode, this option has no effect.
416
.IP "\fB\-d\fR \fIdirectory\fR" 4
417
.IX Item "-d directory"
418
When used with \f(CW\*(C`\-C\*(C'\fR, this causes all generated \fI.class\fR files
419
to be put in the appropriate subdirectory of \fIdirectory\fR.  By
420
default they will be put in subdirectories of the current working
421
directory.
422
.IP "\fB\-fno\-bounds\-check\fR" 4
423
.IX Item "-fno-bounds-check"
424
By default, \fBgcj\fR generates code which checks the bounds of all
425
array indexing operations.  With this option, these checks are omitted, which
426
can improve performance for code that uses arrays extensively.  Note that this
427
can result in unpredictable behavior if the code in question actually does
428
violate array bounds constraints.  It is safe to use this option if you are
429
sure that your code will never throw an \f(CW\*(C`ArrayIndexOutOfBoundsException\*(C'\fR.
430
.IP "\fB\-fno\-store\-check\fR" 4
431
.IX Item "-fno-store-check"
432
Don't generate array store checks.  When storing objects into arrays, a runtime
433
check is normally generated in order to ensure that the object is assignment
434
compatible with the component type of the array (which may not be known
435
at compile-time).  With this option, these checks are omitted.  This can
436
improve performance for code which stores objects into arrays frequently.
437
It is safe to use this option if you are sure your code will never throw an
438
\&\f(CW\*(C`ArrayStoreException\*(C'\fR.
439
.IP "\fB\-fjni\fR" 4
440
.IX Item "-fjni"
441
With \fBgcj\fR there are two options for writing native methods: \s-1CNI\s0
442
and \s-1JNI\s0.  By default \fBgcj\fR assumes you are using \s-1CNI\s0.  If you are
443
compiling a class with native methods, and these methods are implemented
444
using \s-1JNI\s0, then you must use \f(CW\*(C`\-fjni\*(C'\fR.  This option causes
445
\&\fBgcj\fR to generate stubs which will invoke the underlying \s-1JNI\s0
446
methods.
447
.IP "\fB\-fno\-assert\fR" 4
448
.IX Item "-fno-assert"
449
Don't recognize the \f(CW\*(C`assert\*(C'\fR keyword.  This is for compatibility
450
with older versions of the language specification.
451
.IP "\fB\-fno\-optimize\-static\-class\-initialization\fR" 4
452
.IX Item "-fno-optimize-static-class-initialization"
453
When the optimization level is greater or equal to \f(CW\*(C`\-O2\*(C'\fR,
454
\&\fBgcj\fR will try to optimize the way calls into the runtime are made
455
to initialize static classes upon their first use (this optimization
456
isn't carried out if \f(CW\*(C`\-C\*(C'\fR was specified.) When compiling to native
457
code, \f(CW\*(C`\-fno\-optimize\-static\-class\-initialization\*(C'\fR will turn this
458
optimization off, regardless of the optimization level in use.
459
.IP "\fB\-\-disable\-assertions[=\fR\fIclass-or-package\fR\fB]\fR" 4
460
.IX Item "--disable-assertions[=class-or-package]"
461
Don't include code for checking assertions in the compiled code.
462
If \f(CW\*(C`=\f(CIclass\-or\-package\f(CW\*(C'\fR is missing disables assertion code
463
generation for all classes, unless overridden by a more
464
specific \f(CW\*(C`\-\-enable\-assertions\*(C'\fR flag.
465
If \fIclass-or-package\fR is a class name, only disables generating
466
assertion checks within the named class or its inner classes.
467
If \fIclass-or-package\fR is a package name, disables generating
468
assertion checks within the named package or a subpackage.
469
.Sp
470
By default, assertions are enabled when generating class files
471
or when not optimizing, and disabled when generating optimized binaries.
472
.IP "\fB\-\-enable\-assertions[=\fR\fIclass-or-package\fR\fB]\fR" 4
473
.IX Item "--enable-assertions[=class-or-package]"
474
Generates code to check assertions.  The option is perhaps misnamed,
475
as you still need to turn on assertion checking at run-time,
476
and we don't support any easy way to do that.
477
So this flag isn't very useful yet, except to partially override
478
\&\f(CW\*(C`\-\-disable\-assertions\*(C'\fR.
479
.IP "\fB\-findirect\-dispatch\fR" 4
480
.IX Item "-findirect-dispatch"
481
\&\fBgcj\fR has a special binary compatibility \s-1ABI\s0, which is enabled
482
by the \f(CW\*(C`\-findirect\-dispatch\*(C'\fR option.  In this mode, the code
483
generated by \fBgcj\fR honors the binary compatibility guarantees
484
in the Java Language Specification, and the resulting object files do
485
not need to be directly linked against their dependencies.  Instead,
486
all dependencies are looked up at runtime.  This allows free mixing of
487
interpreted and compiled code.
488
.Sp
489
Note that, at present, \f(CW\*(C`\-findirect\-dispatch\*(C'\fR can only be used
490
when compiling \fI.class\fR files.  It will not work when compiling
491
from source.  \s-1CNI\s0 also does not yet work with the binary compatibility
492
\&\s-1ABI\s0.  These restrictions will be lifted in some future release.
493
.Sp
494
However, if you compile \s-1CNI\s0 code with the standard \s-1ABI\s0, you can call
495
it from code built with the binary compatibility \s-1ABI\s0.
496
.IP "\fB\-fbootstrap\-classes\fR" 4
497
.IX Item "-fbootstrap-classes"
498
This option can be use to tell \f(CW\*(C`libgcj\*(C'\fR that the compiled classes
499
should be loaded by the bootstrap loader, not the system class loader.
500
By default, if you compile a class and link it into an executable, it
501
will be treated as if it was loaded using the system class loader.
502
This is convenient, as it means that things like
503
\&\f(CW\*(C`Class.forName()\*(C'\fR will search \fB\s-1CLASSPATH\s0\fR to find the
504
desired class.
505
.IP "\fB\-freduced\-reflection\fR" 4
506
.IX Item "-freduced-reflection"
507
This option causes the code generated by \fBgcj\fR to contain a
508
reduced amount of the class meta-data used to support runtime
509
reflection. The cost of this savings is the loss of
510
the ability to use certain reflection capabilities of the standard
511
Java runtime environment. When set all meta-data except for that
512
which is needed to obtain correct runtime semantics is eliminated.
513
.Sp
514
For code that does not use reflection (i.e. serialization, \s-1RMI\s0, \s-1CORBA\s0
515
or call methods in the \f(CW\*(C`java.lang.reflect\*(C'\fR package),
516
\&\f(CW\*(C`\-freduced\-reflection\*(C'\fR will result in proper operation with a
517
savings in executable code size.
518
.Sp
519
\&\s-1JNI\s0 (\f(CW\*(C`\-fjni\*(C'\fR) and the binary compatibility \s-1ABI\s0
520
(\f(CW\*(C`\-findirect\-dispatch\*(C'\fR) do not work properly without full
521
reflection meta-data.  Because of this, it is an error to use these options
522
with \f(CW\*(C`\-freduced\-reflection\*(C'\fR.
523
.Sp
524
\&\fBCaution:\fR If there is no reflection meta-data, code that uses
525
a \f(CW\*(C`SecurityManager\*(C'\fR may not work properly.  Also calling
526
\&\f(CW\*(C`Class.forName()\*(C'\fR may fail if the calling method has no
527
reflection meta-data.
528
.Sh "Configure-time Options"
529
.IX Subsection "Configure-time Options"
530
Some \fBgcj\fR code generations options affect the resulting \s-1ABI\s0, and
531
so can only be meaningfully given when \f(CW\*(C`libgcj\*(C'\fR, the runtime
532
package, is configured.  \f(CW\*(C`libgcj\*(C'\fR puts the appropriate options from
533
this group into a \fBspec\fR file which is read by \fBgcj\fR.  These
534
options are listed here for completeness; if you are using \f(CW\*(C`libgcj\*(C'\fR
535
then you won't want to touch these options.
536
.IP "\fB\-fuse\-boehm\-gc\fR" 4
537
.IX Item "-fuse-boehm-gc"
538
This enables the use of the Boehm \s-1GC\s0 bitmap marking code.  In particular
539
this causes \fBgcj\fR to put an object marking descriptor into each
540
vtable.
541
.IP "\fB\-fhash\-synchronization\fR" 4
542
.IX Item "-fhash-synchronization"
543
By default, synchronization data (the data used for \f(CW\*(C`synchronize\*(C'\fR,
544
\&\f(CW\*(C`wait\*(C'\fR, and \f(CW\*(C`notify\*(C'\fR) is pointed to by a word in each object.
545
With this option \fBgcj\fR assumes that this information is stored in a
546
hash table and not in the object itself.
547
.IP "\fB\-fuse\-divide\-subroutine\fR" 4
548
.IX Item "-fuse-divide-subroutine"
549
On some systems, a library routine is called to perform integer
550
division.  This is required to get exception handling correct when
551
dividing by zero.
552
.IP "\fB\-fcheck\-references\fR" 4
553
.IX Item "-fcheck-references"
554
On some systems it's necessary to insert inline checks whenever
555
accessing an object via a reference.  On other systems you won't need
556
this because null pointer accesses are caught automatically by the
557
processor.
558
.IP "\fB\-fuse\-atomic\-builtins\fR" 4
559
.IX Item "-fuse-atomic-builtins"
560
On some systems, gcc can generate code for built-in atomic operations.
561
Use this option to force gcj to use these builtins when compiling Java
562
code.  Where this capability is present it should be automatically
563
detected, so you won't usually need to use this option.
564
.SH "SEE ALSO"
565
.IX Header "SEE ALSO"
566
\&\fIgcc\fR\|(1), \fIgcjh\fR\|(1), \fIgjnih\fR\|(1), \fIgij\fR\|(1), \fIjcf\-dump\fR\|(1), \fIgfdl\fR\|(7),
567
and the Info entries for \fIgcj\fR and \fIgcc\fR.
568
.SH "COPYRIGHT"
569
.IX Header "COPYRIGHT"
570
Copyright (c) 2001, 2002, 2003, 2004, 2005, 2006, 2007, 2008 Free Software Foundation, Inc.
571
.PP
572
Permission is granted to copy, distribute and/or modify this document
573
under the terms of the \s-1GNU\s0 Free Documentation License, Version 1.2 or
574
any later version published by the Free Software Foundation; with no
575
Invariant Sections, the Front-Cover Texts being (a) (see below), and
576
with the Back-Cover Texts being (b) (see below).
577
A copy of the license is included in the
578
man page \fIgfdl\fR\|(7).
579
.PP
580
(a) The \s-1FSF\s0's Front-Cover Text is:
581
.PP
582
.Vb 1
583
\&     A GNU Manual
584
.Ve
585
.PP
586
(b) The \s-1FSF\s0's Back-Cover Text is:
587
.PP
588
.Vb 3
589
\&     You have freedom to copy and modify this GNU Manual, like GNU
590
\&     software.  Copies published by the Free Software Foundation raise
591
\&     funds for GNU development.
592
.Ve

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