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This file contains information about GCC releases up to GCC 2.8.1, and

a tiny bit of information on EGCS.

For details of changes in EGCS releases and GCC 2.95 and later releases,

see the release notes on the GCC web site or the file NEWS which contains

the most relevant parts of those release notes in text form.

Changes in GCC for EGCS (that are not listed in the web release notes)

---------------------------------------------------------------------

The compiler now supports the "ADDRESSOF" optimization which can significantly

reduce the overhead for certain inline calls (and inline calls in general).

Compile time for certain programs using large constant initializers has been

improved (affects glibc significantly).

Various improvements have been made to better support cross compilations.  They

are still not easy, but they are improving.

Target-specific changes:

    M32r: Major improvements to this port.

    Arm: Includes Thumb and super interworking support.

Noteworthy changes in GCC version 2.8.1

---------------------------------------

Numerous bugs have been fixed and some minor performance

improvements (compilation speed) have been made.

Noteworthy changes in GCC version 2.8.0

---------------------------------------

A major change in this release is the addition of a framework for

exception handling, currently used by C++.  Many internal changes and

optimization improvements have been made.  These increase the

maintainability and portability of GCC.  GCC now uses autoconf to

compute many host parameters.

The following lists changes that add new features or targets.

See cp/NEWS for new features of C++ in this release.

New tools and features:

    The Dwarf 2 debugging information format is supported on ELF systems, and

    is the default for -ggdb where available.  It can also be used for C++.

    The Dwarf version 1 debugging format is also permitted for C++, but

    does not work well.

    gcov.c is provided for test coverage analysis and branch profiling

    analysis is also supported; see -fprofile-arcs, -ftest-coverage,

    and -fbranch-probabilities.

    Support for the Checker memory checking tool.

    New switch, -fstack-check, to check for stack overflow on systems that

    don't have such built into their ABI.

    New switches, -Wundef and -Wno-undef to warn if an undefined identifier

    is evaluated in an #if directive.

    Options -Wall and -Wimplicit now cause GCC to warn about implicit int

    in declarations (e.g. `register i;'), since the C Standard committee

    has decided to disallow this in the next revision of the standard;

    -Wimplicit-function-declarations and -Wimplicit-int are subsets of

    this.

    Option -Wsign-compare causes GCC to warn about comparison of signed and

    unsigned values.

    Add -dI option of cccp for cxref.

New features in configuration, installation and specs file handling:

    New option --enable-c-cpplib to configure script.

    You can use --with-cpu on the configure command to specify the default

    CPU that GCC should generate code for.

    The -specs=file switch allows you to override default specs used in

    invoking programs like cc1, as, etc.

    Allow including one specs file from another and renaming a specs

    variable.

    You can now relocate all GCC files with a single environment variable

    or a registry entry under Windows 95 and Windows NT.

Changes in Objective-C:

    The Objective-C Runtime Library has been made thread-safe.

    The Objective-C Runtime Library contains an interface for creating

    mutexes, condition mutexes, and threads; it requires a back-end

    implementation for the specific platform and/or thread package.

    Currently supported are DEC/OSF1, IRIX, Mach, OS/2, POSIX, PCThreads,

    Solaris, and Windows32.  The --enable-threads parameter can be used

    when configuring GCC to enable and select a thread back-end.

    Objective-C is now configured as separate front-end language to GCC,

    making it more convenient to conditionally build it.

    The internal structures of the Objective-C Runtime Library have

    changed sufficiently to warrant a new version number; now version 8.

    Programs compiled with an older version must be recompiled.

    The Objective-C Runtime Library can be built as a DLL on Windows 95

    and Windows NT systems.

    The Objective-C Runtime Library implements +load.

The following new targets are supported (see also list under each

individual CPU below):

    Embedded target m32r-elf.

    Embedded Hitachi Super-H using ELF.

    RTEMS real-time system on various CPU targets.

    ARC processor.

    NEC V850 processor.

    Matsushita MN10200 processor.

    Matsushita MN10300 processor.

    Sparc and PowerPC running on VxWorks.

    Support both glibc versions 1 and 2 on Linux-based GNU systems.

New features for DEC Alpha systems:

    Allow detailed specification of IEEE fp support:

      -mieee, -mieee-with-inexact, and -mieee-conformant

      -mfp-trap-mode=xxx, -mfp-round-mode=xxx, -mtrap-precision=xxx

    -mcpu=xxx for CPU selection

    Support scheduling parameters for EV5.

    Add support for BWX, CIX, and MAX instruction set extensions.

    Support Linux-based GNU systems.

    Support VMS.

Additional supported processors and systems for MIPS targets:

    MIPS4 instruction set.

    R4100, R4300 and R5000 processors.

    N32 and N64 ABI.

    IRIX 6.2.

    SNI SINIX.

New features for Intel x86 family:

    Add scheduling parameters for Pentium and Pentium Pro.

    Support stabs on Solaris-x86.

    Intel x86 processors running the SCO OpenServer 5 family.

    Intel x86 processors running DG/UX.

    Intel x86 using Cygwin32 or Mingw32 on Windows 95 and Windows NT.

New features for Motorola 68k family:

    Support for 68060 processor.

    More consistent switches to specify processor.

    Motorola 68k family running AUX.

    68040 running pSOS, ELF object files, DBX debugging.

    Coldfire variant of Motorola m68k family.

New features for the HP PA RISC:

    -mspace and -mno-space

    -mlong-load-store and -mno-long-load-store

    -mbig-switch -mno-big-switch

    GCC on the PA requires either gas-2.7 or the HP assembler; for best

    results using GAS is highly recommended.  GAS is required for -g and

    exception handling support.

New features for SPARC-based systems:

    The ultrasparc cpu.

    The sparclet cpu, supporting only a.out file format.

    Sparc running SunOS 4 with the GNU assembler.

    Sparc running the Linux-based GNU system.

    Embedded Sparc processors running the ELF object file format.

    -mcpu=xxx

    -mtune=xxx

    -malign-loops=xxx

    -malign-jumps=xxx

    -malign-functions=xxx

    -mimpure-text and -mno-impure-text

    Options -mno-v8 and -mno-sparclite are no longer supported on SPARC

    targets.  Options -mcypress, -mv8, -msupersparc, -msparclite, -mf930,

    and -mf934 are deprecated and will be deleted in GCC 2.9.  Use

    -mcpu=xxx instead.

New features for rs6000 and PowerPC systems:

    Solaris 2.51 running on PowerPC's.

    The Linux-based GNU system running on PowerPC's.

    -mcpu=604e,602,603e,620,801,823,mpc505,821,860,power2

    -mtune=xxx

    -mrelocatable-lib, -mno-relocatable-lib

    -msim, -mmve, -memb

    -mupdate, -mno-update

    -mfused-madd, -mno-fused-madd

    -mregnames

    -meabi

    -mcall-linux, -mcall-solaris, -mcall-sysv-eabi, -mcall-sysv-noeabi

    -msdata, -msdata=none, -msdata=default, -msdata=sysv, -msdata=eabi

    -memb, -msim, -mmvme

    -myellowknife, -mads

    wchar_t is now of type long as per the ABI, not unsigned short.

    -p/-pg support

    -mcpu=403 now implies -mstrict-align.

    Implement System V profiling.

    Aix 4.1 GCC targets now default to -mcpu=common so that programs

    compiled can be moved between rs6000 and powerpc based systems.  A

    consequence of this is that -static won't work, and that some programs

    may be slightly slower.

    You can select the default value to use for -mcpu=xxx on rs6000 and

    powerpc targets by using the --with-cpu=xxx option when configuring the

    compiler.  In addition, a new options, -mtune=xxx was added that

    selects the machine to schedule for but does not select the

    architecture level.

    Directory names used for storing the multilib libraries on System V

    and embedded PowerPC systems have been shortened to work with commands

    like tar that have fixed limits on pathname size.

New features for the Hitachi H8/300(H):

    -malign-300

    -ms (for the Hitachi H8/S processor)

    -mint32

New features for the ARM:

    -march=xxx, -mtune=xxx, -mcpu=xxx

    Support interworking with Thumb code.

    ARM processor with a.out object format, COFF, or AOF assembler.

    ARM on "semi-hosted" platform.

    ARM running NetBSD.

    ARM running the Linux-based GNU system.

New feature for Solaris systems:

    GCC installation no longer makes a copy of system include files,

    thus insulating GCC better from updates to the operating system.

Noteworthy changes in GCC version 2.7.2

---------------------------------------

A few bugs have been fixed (most notably the generation of an

invalid assembler opcode on some RS/6000 systems).

Noteworthy changes in GCC version 2.7.1

---------------------------------------

This release fixes numerous bugs (mostly minor) in GCC 2.7.0, but

also contains a few new features, mostly related to specific targets.

Major changes have been made in code to support Windows NT.

The following new targets are supported:

        2.9 BSD on PDP-11

        Linux on m68k

        HP/UX version 10 on HP PA RISC (treated like version 9)

        DEC Alpha running Windows NT

When parsing C, GCC now recognizes C++ style `//' comments unless you

specify `-ansi' or `-traditional'.

The PowerPC System V targets (powerpc-*-sysv, powerpc-*-eabi) now use the

calling sequence specified in the System V Application Binary Interface

Processor Supplement (PowerPC Processor ABI Supplement) rather than the calling

sequence used in GCC version 2.7.0.  That calling sequence was based on the AIX

calling sequence without function descriptors.  To compile code for that older

calling sequence, either configure the compiler for powerpc-*-eabiaix or use

the -mcall-aix switch when compiling and linking.

Noteworthy changes in GCC version 2.7.0

---------------------------------------

GCC now works better on systems that use ".obj" and ".exe" instead of

".o" and no extension.  This involved changes to the driver program,

gcc.c, to convert ".o" names to ".obj" and to GCC's Makefile to use

".obj" and ".exe" in filenames that are not targets.  In order to

build GCC on such systems, you may need versions of GNU make and/or

compatible shells.  At this point, this support is preliminary.

Object file extensions of ".obj" and executable file extensions of

".exe" are allowed when using appropriate version of GNU Make.

Numerous enhancements were made to the __attribute__ facility including

more attributes and more places that support it.  We now support the

"packed", "nocommon", "noreturn", "volatile", "const", "unused",

"transparent_union", "constructor", "destructor", "mode", "section",

"align", "format", "weak", and "alias" attributes.  Each of these

names may also be specified with added underscores, e.g., "__packed__".

__attribute__ may now be applied to parameter definitions, function

definitions, and structure, enum, and union definitions.

GCC now supports returning more structures in registers, as specified by

many calling sequences (ABIs), such as on the HP PA RISC.

A new option '-fpack-struct' was added to automatically pack all structure

members together without holes.

There is a new library (cpplib) and program (cppmain) that at some

point will replace cpp (aka cccp).  To use cppmain as cpp now, pass

the option CCCP=cppmain to make.  The library is already used by the

fix-header program, which should speed up the fixproto script.

New options for supported targets:

    GNU on many targets.

    NetBSD on MIPS, m68k, VAX, and x86.

    LynxOS on x86, m68k, Sparc, and RS/6000.

    VxWorks on many targets.

    Windows/NT on x86 architecture.  Initial support for Windows/NT on Alpha

    (not fully working).

    Many embedded targets, specifically UDI on a29k, aout, coff, elf,

    and vsta "operating systems" on m68k, m88k, mips, sparc, and x86.

Additional support for x86 (i386, i486, and Pentium):

    Work with old and new linkers for Linux-based GNU systems,

        supporting both a.out and ELF.

    FreeBSD on x86.

    Stdcall convention.

    -malign-double, -mregparm=, -malign-loops= and -malign-jumps=  switches.

    On ISC systems, support -Xp like -posix.

Additions for RS/6000:

    Instruction scheduling information for PowerPC 403.

    AIX 4.1 on PowerPC.

    -mstring and -mno-string.

    -msoft-float and floating-point emulation included.

    Preliminary support for PowerPC System V.4 with or without the GNU as.

    Preliminary support for EABI.

    Preliminary support for 64-bit systems.

    Both big and little endian systems.

New features for MIPS-based systems:

    r4650.

    mips4 and R8000.

    Irix 6.0.

    64-bit ABI.

    Allow dollar signs in labels on SGI/Irix 5.x.

New support for HP PA RISC:

    Generation of PIC (requires binutils-2.5.2.u6 or later).

    HP-UX version 9 on HP PA RISC (dynamically links even with -g).

    Processor variants for HP PA RISC: 700, 7100, and 7100LC.

    Automatic generation of long calls when needed.

    -mfast-indirect-calls for kernels and static binaries.

    The called routine now copies arguments passed by invisible reference,

    as required by the calling standard.

Other new miscellaneous target-specific support:

    -mno-multm on a29k.

    -mold-align for i960.

    Configuration for "semi-hosted" ARM.

    -momit-leaf-frame-pointer for M88k.

    SH3 variant of Hitachi Super-H and support both big and little endian.

Changes to Objective-C:

    Bare-bones implementation of NXConstantString has been added,

    which is invoked by the @"string" directive.

    Class * has been changed to Class to conform to the NextSTEP and

    OpenStep runtime.

    Enhancements to make dynamic loading easier.

    The module version number has been updated to Version 7, thus existing

    code will need to be recompiled to use the current run-time library.

GCC now supports the ISO Normative Addendum 1 to the C Standard.

As a result:

    The header  defines macros for C programs written

    in national variants of ISO 646.

    The following digraph tokens are supported:

        <:	:>        <%	%>        %:      %:%:

    These behave like the following, respectively:

        [       ]       {       }       #       ##

    Digraph tokens are supported unless you specify the `-traditional'

    option; you do not need to specify `-ansi' or `-trigraphs'.  Except

    for contrived and unlikely examples involving preprocessor

    stringizing, digraph interpretation doesn't change the meaning of

    programs; this is unlike trigraph interpretation, which changes the

    meanings of relatively common strings.

    The macro __STDC_VERSION__ has the value 199409L.

  As usual, for full conformance to the standard, you also need a

  C library that conforms.

The following lists changes that have been made to g++.  If some

features mentioned below sound unfamiliar, you will probably want to

look at the recently-released public review copy of the C++ Working

Paper.  For PostScript and PDF (Adobe Acrobat) versions, see the

archive at ftp://research.att.com/dist/stdc++/WP.  For HTML and ASCII

versions, see ftp://ftp.cygnus.com/pub/g++.  On the web, see

http://www.cygnus.com/~mrs/wp-draft.

The scope of variables declared in the for-init-statement has been changed

to conform to http://www.cygnus.com/~mrs/wp-draft/stmt.html#stmt.for; as a

result, packages such as groff 1.09 will not compile unless you specify the

-fno-for-scope flag.  PLEASE DO NOT REPORT THIS AS A BUG; this is a change

mandated by the C++ standardization committee.

Binary incompatibilities:

    The builtin 'bool' type is now the size of a machine word on RISC targets,

    for code efficiency; it remains one byte long on CISC targets.

    Code that does not use #pragma interface/implementation will most

    likely shrink dramatically, as g++ now only emits the vtable for a

    class in the translation unit where its first non-inline, non-abstract

    virtual function is defined.

    Classes that do not define the copy constructor will sometimes be

    passed and returned in registers.  This may illuminate latent bugs in

    your code.

Support for automatic template instantiation has *NOT* been added, due

to a disagreement over design philosophies.

Support for exception handling has been improved; more targets are now

supported, and throws will use the RTTI mechanism to match against the

catch parameter type.  Optimization is NOT SUPPORTED with

-fhandle-exceptions; no need to report this as a bug.

Support for Run-Time Type Identification has been added with -frtti.

This support is still in alpha; one major restriction is that any file

compiled with -frtti must include .

Preliminary support for namespaces has been added.  This support is far

from complete, and probably not useful.

Synthesis of compiler-generated constructors, destructors and

assignment operators is now deferred until the functions are used.

The parsing of expressions such as `a ? b : c = 1' has changed from

`(a ? b : c) = 1' to `a : b ? (c = 1)'.

The code generated for testing conditions, especially those using ||

and &&, is now more efficient.

The operator keywords and, and_eq, bitand, bitor, compl, not, not_eq,

or, or_eq, xor and xor_eq are now supported.  Use -ansi or

-foperator-names to enable them.

The 'explicit' keyword is now supported.  'explicit' is used to mark

constructors and type conversion operators that should not be used

implicitly.

g++ now accepts the typename keyword, though it currently has no

semantics; it can be a no-op in the current template implementation.

You may want to start using it in your code, however, since the

pending rewrite of the template implementation to compile STL properly

(perhaps for 2.8.0, perhaps not) will require you to use it as

indicated by the current draft.

Handling of user-defined type conversion has been overhauled so that

type conversion operators are now found and used properly in

expressions and function calls.

-fno-strict-prototype now only applies to function declarations with

"C" linkage.

g++ now warns about 'if (x=0)' with -Wparentheses or -Wall.

#pragma weak and #pragma pack are supported on System V R4 targets, as

are various other target-specific #pragmas supported by gcc.

new and delete of const types is now allowed (with no additional

semantics).

Explicit instantiation of template methods is now supported.  Also,

'inline template class foo;' can be used to emit only the vtable

for a template class.

With -fcheck-new, g++ will check the return value of all calls to

operator new, and not attempt to modify a returned null pointer.

The template instantiation code now handles more conversions when

passing to a parameter that does not depend on template arguments.

This means that code like 'string s; cout << s;' now works.

Invalid jumps in a switch statement past declarations that require

initializations are now caught.

Functions declared 'extern inline' now have the same linkage semantics

as inline member functions.  On supported targets, where previously

these functions (and vtables, and template instantiations) would have

been defined statically, they will now be defined as weak symbols so

that only one out-of-line definition is used.

collect2 now demangles linker output, and c++filt has become part of

the gcc distribution.

Noteworthy changes in GCC version 2.6.3:

A few more bugs have been fixed.

Noteworthy changes in GCC version 2.6.2:

A few bugs have been fixed.

Names of attributes can now be preceded and followed by double underscores.

Noteworthy changes in GCC version 2.6.1:

Numerous (mostly minor) bugs have been fixed.

The following new configurations are supported:

        GNU on x86 (instead of treating it like MACH)

        NetBSD on Sparc and Motorola 68k

        AIX 4.1 on RS/6000 and PowerPC systems

        Sequent DYNIX/ptx 1.x and 2.x.

        Both COFF and ELF configurations on AViiON without using /bin/gcc

        Windows/NT on x86 architecture; preliminary

        AT&T DSP1610 digital signal processor chips

        i960 systems on bare boards using COFF

        PDP11; target only and not extensively tested

The -pg option is now supported for Alpha under OSF/1 V3.0 or later.

Files with an extension of ".c++" are treated as C++ code.

The -Xlinker and -Wl arguments are now passed to the linker in the

position they were specified on the command line.  This makes it

possible, for example, to pass flags to the linker about specific

object files.

The use of positional arguments to the configure script is no longer

recommended.  Use --target= to specify the target; see the GCC manual.

The 386 now supports two new switches: -mreg-alloc= changes

the default register allocation order used by the compiler, and

-mno-wide-multiply disables the use of the mul/imul instructions that

produce 64 bit results in EAX:EDX from 32 bit operands to do long long

multiplies and 32-bit division by constants.

Noteworthy changes in GCC version 2.6.0:

Numerous bugs have been fixed, in the C and C++ front-ends, as

well as in the common compiler code.

This release includes the C, Objective-C, and C++ compilers.  However,

we have moved the files for the C++ compiler (G++) files to a

subdirectory, cp.  Subsequent releases of GCC will split these files

to a separate TAR file.

The G++ team has been tracking the development of the ANSI standard for C++.

Here are some new features added from the latest working paper:

        * built-in boolean type 'bool', with constants 'true' and 'false'.

        * array new and delete (operator new [] and delete []).

        * WP-conforming lifetime of temporaries.

        * explicit instantiation of templates (template class A;),

          along with an option (-fno-implicit-templates) to disable emission

          of implicitly instantiated templates, obsoletes -fexternal-templates.

        * static member constants (static const int foo = 4; within the

          class declaration).

Many error messages have been improved to tell the user more about the

problem.  Conformance checking with -pedantic-errors has been

improved.  G++ now compiles Fresco.

There is now an experimental implementation of virtual functions using

thunks instead of Cfront-style vtables, enabled with -fvtable-thunks.

This option also enables a heuristic which causes the compiler to only

emit the vtable in the translation unit where its first non-inline

virtual function is defined; using this option and

-fno-implicit-templates, users should be able to avoid #pragma

interface/implementation altogether.

Signatures have been added as a GNU C++ extension.  Using the option

-fhandle-signatures, users are able to turn on recognition of

signatures.  A short introduction on signatures is in the section

`Extension to the C++ Language' in the manual.

The `g++' program is now a C program, rather than a shell script.

Lots and lots and lots of bugs fixes, in nested types, access control,

pointers to member functions, the parser, templates, overload

resolution, etc, etc.

There have been two major enhancements to the Objective-C compiler:

1) Added portability.  It now runs on Alpha, and some problems with

   message forwarding have been addressed on other platforms.

2) Selectors have been redefined to be pointers to structs like:

   { void *sel_id, char *sel_types }, where the sel_id is the unique

   identifier, the selector itself is no longer unique.

   Programmers should use the new function sel_eq to test selector

   equivalence.

The following major changes have been made to the base compiler and

machine-specific files.

- The MIL-STD-1750A is a new port, but still preliminary.

- The h8/300h is now supported; both the h8/300 and h8/300h ports come

  with 32 bit IEEE 754 software floating point support.

- The 64-bit Sparc (v9) and 64-bit MIPS chips are supported.

- NetBSD is supported on m68k, Intel x86, and pc523 systems and FreeBSD

  on x86.

- COFF is supported on x86, m68k, and Sparc systems running LynxOS.

- 68K systems from Bull and Concurrent are supported and System V

  Release 4 is supported on the Atari.

- GCC supports GAS on the Motorola 3300 (sysV68) and debugging

  (assuming GAS) on the Plexus 68K system.  (However, GAS does not yet

  work on those systems).

- System V Release 4 is supported on MIPS (Tandem).

- For DG/UX, an ELF configuration is now supported, and both the ELF

  and BCS configurations support ELF and COFF object file formats.

- OSF/1 V2.0 is supported on Alpha.

- Function profiling is also supported on Alpha.

- GAS and GDB is supported for Irix 5 (MIPS).

- "common mode" (code that will run on both POWER and PowerPC

  architectures) is now supported for the RS/6000 family; the

  compiler knows about more PPC chips.

- Both NeXTStep 2.1 and 3 are supported on 68k-based architectures.

- On the AMD 29k, the -msoft-float is now supported, as well as

  -mno-sum-in-toc for RS/6000, -mapp-regs and -mflat for Sparc, and

  -membedded-pic for MIPS.

- GCC can now convert division by integer constants into the equivalent

  multiplication and shift operations when that is faster than the

  division.

- Two new warning options, -Wbad-function-cast and

  -Wmissing-declarations have been added.

- Configurations may now add machine-specific __attribute__ options on

  type; many machines support the `section' attribute.

- The -ffast-math flag permits some optimization that violate strict

  IEEE rules, such as converting X * 0.0 to 0.0.

Noteworthy changes in GCC version 2.5.8:

This release only fixes a few serious bugs.  These include fixes for a

bug that prevented most programs from working on the RS/6000, a bug

that caused invalid assembler code for programs with a `switch'

statement on the NS32K, a G++ problem that caused undefined names in

some configurations, and several less serious problems, some of which

can affect most configuration.

Noteworthy change in GCC version 2.5.7:

This release only fixes a few bugs, one of which was causing bootstrap

compare errors on some systems.

Noteworthy change in GCC version 2.5.6:

A few backend bugs have been fixed, some of which only occur on one

machine.

The C++ compiler in 2.5.6 includes:

 * fixes for some common crashes

 * correct handling of nested types that are referenced as `foo::bar'

 * spurious warnings about friends being declared static and never

   defined should no longer appear

 * enums that are local to a method in a class, or a class that's

   local to a function, are now handled correctly.  For example:

       class foo { void bar () { enum { x, y } E; x; } };

       void bar () { class foo { enum { x, y } E; E baz; }; }

Noteworthy change in GCC version 2.5.5:

A large number of C++ bugs have been fixed.

The fixproto script adds prototypes conditionally on __cplusplus.

Noteworthy change in GCC version 2.5.4:

A bug fix in passing of structure arguments for the HP-PA architecture

makes code compiled with GCC 2.5.4 incompatible with code compiled

with earlier versions (if it passes struct arguments of 33 to 64 bits,

interspersed with other types of arguments).

Noteworthy change in gcc version 2.5.3:

The method of "mangling" C++ function names has been changed.  So you

must recompile all C++ programs completely when you start using GCC

2.5.  Also, GCC 2.5 requires libg++ version 2.5.  Earlier libg++

versions won't work with GCC 2.5.  (This is generally true--GCC

version M.N requires libg++ version M.N.)

Noteworthy GCC changes in version 2.5:

* There is now support for the IBM 370 architecture as a target.

Currently the only operating system supported is MVS; GCC does not run

on MVS, so you must produce .s files using GCC as a cross compiler,

then transfer them to MVS to assemble them.  This port is not reliable

yet.

* The Power PC is now supported.

* The i860-based Paragon machine is now supported.

* The Hitachi 3050 (an HP-PA machine) is now supported.

* The variable __GNUC_MINOR__ holds the minor version number of GCC, as

an integer.  For version 2.5.X, the value is 5.

* In C, initializers for static and global variables are now processed

an element at a time, so that they don't need a lot of storage.

* The C syntax for specifying which structure field comes next in an

initializer is now `.FIELDNAME='.  The corresponding syntax for

array initializers is now `[INDEX]='.  For example,

  char whitespace[256]

    = { [' '] = 1, ['\t'] = 1, ['\n'] = 1 };

This was changed to accord with the syntax proposed by the Numerical

C Extensions Group (NCEG).

* Complex numbers are now supported in C.  Use the keyword __complex__

to declare complex data types.  See the manual for details.

* GCC now supports `long double' meaningfully on the Sparc (128-bit

floating point) and on the 386 (96-bit floating point).  The Sparc

support is enabled on Solaris 2.x because earlier system versions

(SunOS 4) have bugs in the emulation.

* All targets now have assertions for cpu, machine and system.  So you

can now use assertions to distinguish among all supported targets.

* Nested functions in C may now be inline.  Just declare them inline

in the usual way.

* Packed structure members are now supported fully; it should be possible

to access them on any supported target, no matter how little alignment

they have.

* To declare that a function does not return, you must now write

something like this (works only in 2.5):

    void fatal () __attribute__ ((noreturn));

or like this (works in older versions too):

    typedef void voidfn ();

    volatile voidfn fatal;

It used to be possible to do so by writing this:

    volatile void fatal ();

but it turns out that ANSI C requires that to mean something

else (which is useless).

Likewise, to declare that a function is side-effect-free

so that calls may be deleted or combined, write

something like this (works only in 2.5):

    int computation () __attribute__ ((const));

or like this (works in older versions too):

    typedef int intfn ();

    const intfn computation;

* The new option -iwithprefixbefore specifies a directory to add to

the search path for include files in the same position where -I would

put it, but uses the specified prefix just like -iwithprefix.

* Basic block profiling has been enhanced to record the function the

basic block comes from, and if the module was compiled for debugging,

the line number and filename.  A default version of the basic block

support module has been added to libgcc2 that appends the basic block

information to a text file 'bb.out'.  Machine descriptions can now

override the basic block support module in the target macro file.

New features in g++:

* The new flag `-fansi-overloading' for C++.  Use a newly implemented

scheme of argument matching for C++.  It makes g++ more accurately

obey the rules set down in Chapter 13 of the Annotated C++ Reference

Manual (the ARM).  This option will be turned on by default in a

future release.

* The -finline-debug flag is now gone (it was never really used by the

  compiler).

* Recognizing the syntax for pointers to members, e.g., "foo::*bar", has been

  dramatically improved.  You should not get any syntax errors or incorrect

  runtime results while using pointers to members correctly; if you do, it's

  a definite bug.

* Forward declaration of an enum is now flagged as an error.

* Class-local typedefs are now working properly.

* Nested class support has been significantly improved.  The compiler

  will now (in theory) support up to 240 nested classes before hitting

  other system limits (like memory size).

* There is a new C version of the `g++' driver, to replace the old

  shell script.  This should significantly improve the performance of

  executing g++ on a system where a user's PATH environment variable

  references many NFS-mounted filesystems.  This driver also works

  under MS-DOS and OS/2.

* The ANSI committee working on the C++ standard has adopted a new

  keyword `mutable'.  This will allow you to make a specific member be

  modifiable in an otherwise const class.

Noteworthy GCC changes in version 2.4.4:

  A crash building g++ on various hosts (including m68k) has been

  fixed.  Also the g++ compiler no longer reports incorrect

  ambiguities in some situations where they do not exist, and

  const template member functions are now being found properly.

Noteworthy GCC changes in version 2.4:

* On each target, the default is now to return short structures

compatibly with the "usual" compiler on that target.

For most targets, this means the default is to return all structures

in memory, like long structures, in whatever way is used on that

target.  Use -freg-struct-return to enable returning short structures

(and unions) in registers.

This change means that newly compiled binaries are incompatible with

binaries compiled with previous versions of GCC.

On some targets, GCC is itself the usual compiler.  On these targets,

the default way to return short structures is still in registers.

Use -fpcc-struct-return to tell GCC to return them in memory.

* There is now a floating point emulator which can imitate the way all

supported target machines do floating point arithmetic.

This makes it possible to have cross compilation to and from the VAX,

and between machines of different endianness.  However, this works

only when the target machine description is updated to use the new

facilities, and not all have been updated.

This also makes possible support for longer floating point types.

GCC 2.4 supports extended format on the 68K if you use `long double',

for targets that have a 68881.  (When we have run time library

routines for extended floating point, then `long double' will use

extended format on all 68K targets.)

We expect to support extended floating point on the i386 and Sparc in

future versions.

* Building GCC now automatically fixes the system's header files.

This should require no attention.

* GCC now installs an unsigned data type as size_t when it fixes the

header files (on all but a handful of old target machines).

Therefore, the bug that size_t failed to be unsigned is fixed.

* Building and installation are now completely separate.

All new files are constructed during the build process;

installation just copies them.

* New targets supported: Clipper, Hitachi SH, Hitachi 8300, and Sparc

Lite.

* A totally new and much better Objective C run time system is included.

* Objective C supports many new features.  Alas, I can't describe them

since I don't use that language; however, they are the same ones

supported in recent versions of the NeXT operating system.

* The builtin functions __builtin_apply_args, __builtin_apply and

__builtin_return let you record the arguments and returned

value of a function without knowing their number or type.

* The builtin string variables __FUNCTION__ and __PRETTY_FUNCTION__

give the name of the function in the source, and a pretty-printed

version of the name.  The two are the same in C, but differ in C++.

* Casts to union types do not yield lvalues.

* ## before an empty rest argument discards the preceding sequence

of non-whitespace characters from the macro definition.

(This feature is subject to change.)

New features specific to C++:

* The manual contains a new section ``Common Misunderstandings with

GNU C++'' that C++ users should read.

* #pragma interface and #pragma implementation let you use the same

C++ source file for both interface and implementation.

However, this mechanism is still in transition.

* Named returned values let you avoid an extra constructor call

when a function result has a class type.

* The C++ operators ? yield min and max, respectively.

* C++ gotos can exit a block safely even if the block has

aggregates that require destructors.

* gcc defines the macro __GNUG__ when compiling C++ programs.