1 Noteworthy changes in GCC after EGCS 1.1.
2 -----------------------------------------
6 RS6000/PowerPC: -mcpu=401 was added as an alias for -mcpu=403. -mcpu=e603e
7 was added to do -mcpu=603e and -msoft-float.
9 Noteworthy changes in GCC for EGCS 1.1.
10 ---------------------------------------
12 The compiler now implements global common subexpression elimination (gcse) as
13 well as global constant/copy propagation. (link to gcse page).
15 More major improvements have been made to the alias analysis code. A new
16 option to allow front-ends to provide alias information to the optimizers
17 has also been added (-fstrict-aliasing). -fstrict-aliasing is off by default
18 now, but will be enabled by default in the future. (link to alias page)
20 Major changes continue in the exception handling support. This release
21 includes some changes to reduce static overhead for exception handling. It
22 also includes some major changes to the setjmp/longjmp based EH mechanism to
23 make it less pessimistic. And finally, major infrastructure improvements
24 to the dwarf2 EH mechanism have been made to make our EH support extensible.
26 We have fixed the infamous security problems with temporary files.
28 The "regmove" optimization pass has been nearly completely rewritten. It now
29 uses much more information about the target to determine profitability of
32 The compiler now recomputes register usage information immediately before
33 register allocation. Previously such information was only not kept up to
34 date after instruction combination which led to poor register allocation
35 choices by our priority based register allocator.
37 The register reloading phase of the compiler has been improved to better
38 optimize spill code. This primarily helps targets which generate lots of
39 spills (like the x86 ports and many register poor embedded ports).
41 A few changes in the heuristics used by the register allocator and scheduler
42 have been made which can significantly improve performance for certain
45 The compiler's branch shortening algorithms have been significantly improved
46 to work better on targets which align jump targets.
48 The compiler now supports the "ADDRESSOF" optimization which can significantly
49 reduce the overhead for certain inline calls (and inline calls in general).
51 The compiler now supports a code size optimization switch (-Os). When enabled
52 the compiler will prefer optimizations which improve code size over those
53 which improve code speed.
55 The compiler has been improved to completely eliminate library calls which
56 compute constant values. This is particularly useful on machines which
57 do not have integer mul/div or floating point support on-chip.
59 GCC now supports a "--help" option to print detailed help information.
61 cpplib has been greatly improved. It is probably useable for some sites now
62 (major missing feature is trigraphs).
64 Memory footprint for the compiler has been significantly reduced for certain
67 Build time improvements for targets which support lots of sched parameters
68 (alpha and mips primarily).
70 Compile time for certain programs using large constant initializers has been
71 improved (effects glibc significantly).
73 Plus an incredible number of infrastructure changes, warning fixes, bugfixes
74 and local optimizations.
76 Various improvements have been made to better support cross compilations. They
77 are still not easy, but they are improving.
81 Sparc: Now includes V8 plus and V9 support, lots of tuning for Ultrasparcs
82 and uses the Haifa scheduler by default.
84 Alpha: EV6 tuned, optimized expansion of memcpy/bzero.
86 x86: Data in the static store is aligned per Intel recommendations. Jump
87 targets are aligned per Intel recommendations. Improved epilogue
88 sequences for Pentium chips. Backend improvements which should help
89 register allocation on all x86 variants. Support for PPro conditional
90 move instructions has been fixed and enabled. Random changes
91 throughout the port to make generated code more Pentium friendly.
92 Improved support for 64bit integer operations.
93 Unixware 7, a System V Release 5 target is now supported.
94 SCO OpenServer targets can support GAS. See gcc/INSTALL for details.
96 RS6000/PowerPC: Includes AIX4.3 support as well as PowerPC64 support.
97 Haifa instruction scheduling is enabled by default now.
99 MIPS: Multiply/Multiply-Add support has been largely rewritten to generate
100 more efficient code. Includes mips16 support.
102 M68K: Various micro-optimizations and Coldfire fixes.
104 M32r: Major improvements to this port.
106 Arm: Includes Thumb and super interworking support.
108 EGCS includes all gcc2 changes up to and including the June 9, 1998 snapshot.
111 Noteworthy changes in GCC version 2.8.1
112 ---------------------------------------
114 Numerous bugs have been fixed and some minor performance
115 improvements (compilation speed) have been made.
117 Noteworthy changes in GCC version 2.8.0
118 ---------------------------------------
120 A major change in this release is the addition of a framework for
121 exception handling, currently used by C++. Many internal changes and
122 optimization improvements have been made. These increase the
123 maintainability and portability of GCC. GCC now uses autoconf to
124 compute many host parameters.
126 The following lists changes that add new features or targets.
128 See cp/NEWS for new features of C++ in this release.
130 New tools and features:
132 The Dwarf 2 debugging information format is supported on ELF systems, and
133 is the default for -ggdb where available. It can also be used for C++.
134 The Dwarf version 1 debugging format is also permitted for C++, but
137 gcov.c is provided for test coverage analysis and branch profiling
138 analysis is also supported; see -fprofile-arcs, -ftest-coverage,
139 and -fbranch-probabilities.
141 Support for the Checker memory checking tool.
143 New switch, -fstack-check, to check for stack overflow on systems that
144 don't have such built into their ABI.
146 New switches, -Wundef and -Wno-undef to warn if an undefined identifier
147 is evaluated in an #if directive.
149 Options -Wall and -Wimplicit now cause GCC to warn about implicit int
150 in declarations (e.g. `register i;'), since the C Standard committee
151 has decided to disallow this in the next revision of the standard;
152 -Wimplicit-function-declarations and -Wimplicit-int are subsets of
155 Option -Wsign-compare causes GCC to warn about comparison of signed and
158 Add -dI option of cccp for cxref.
160 New features in configuration, installation and specs file handling:
162 New option --enable-c-cpplib to configure script.
164 You can use --with-cpu on the configure command to specify the default
165 CPU that GCC should generate code for.
167 The -specs=file switch allows you to override default specs used in
168 invoking programs like cc1, as, etc.
170 Allow including one specs file from another and renaming a specs
173 You can now relocate all GCC files with a single environment variable
174 or a registry entry under Windows 95 and Windows NT.
176 Changes in Objective-C:
178 The Objective-C Runtime Library has been made thread-safe.
180 The Objective-C Runtime Library contains an interface for creating
181 mutexes, condition mutexes, and threads; it requires a back-end
182 implementation for the specific platform and/or thread package.
183 Currently supported are DEC/OSF1, IRIX, Mach, OS/2, POSIX, PCThreads,
184 Solaris, and Windows32. The --enable-threads parameter can be used
185 when configuring GCC to enable and select a thread back-end.
187 Objective-C is now configured as separate front-end language to GCC,
188 making it more convenient to conditionally build it.
190 The internal structures of the Objective-C Runtime Library have
191 changed sufficiently to warrant a new version number; now version 8.
192 Programs compiled with an older version must be recompiled.
194 The Objective-C Runtime Library can be built as a DLL on Windows 95
195 and Windows NT systems.
197 The Objective-C Runtime Library implements +load.
199 The following new targets are supported (see also list under each
200 individual CPU below):
202 Embedded target m32r-elf.
203 Embedded Hitachi Super-H using ELF.
204 RTEMS real-time system on various CPU targets.
207 Matsushita MN10200 processor.
208 Matsushita MN10300 processor.
209 Sparc and PowerPC running on VxWorks.
210 Support both glibc versions 1 and 2 on Linux-based GNU systems.
212 New features for DEC Alpha systems:
214 Allow detailed specification of IEEE fp support:
215 -mieee, -mieee-with-inexact, and -mieee-conformant
216 -mfp-trap-mode=xxx, -mfp-round-mode=xxx, -mtrap-precision=xxx
217 -mcpu=xxx for CPU selection
218 Support scheduling parameters for EV5.
219 Add support for BWX, CIX, and MAX instruction set extensions.
220 Support Linux-based GNU systems.
223 Additional supported processors and systems for MIPS targets:
225 MIPS4 instruction set.
226 R4100, R4300 and R5000 processors.
231 New features for Intel x86 family:
233 Add scheduling parameters for Pentium and Pentium Pro.
234 Support stabs on Solaris-x86.
235 Intel x86 processors running the SCO OpenServer 5 family.
236 Intel x86 processors running DG/UX.
237 Intel x86 using Cygwin32 or Mingw32 on Windows 95 and Windows NT.
239 New features for Motorola 68k family:
241 Support for 68060 processor.
242 More consistent switches to specify processor.
243 Motorola 68k family running AUX.
244 68040 running pSOS, ELF object files, DBX debugging.
245 Coldfire variant of Motorola m68k family.
247 New features for the HP PA RISC:
249 -mspace and -mno-space
250 -mlong-load-store and -mno-long-load-store
251 -mbig-switch -mno-big-switch
253 GCC on the PA requires either gas-2.7 or the HP assembler; for best
254 results using GAS is highly recommended. GAS is required for -g and
255 exception handling support.
257 New features for SPARC-based systems:
260 The sparclet cpu, supporting only a.out file format.
261 Sparc running SunOS 4 with the GNU assembler.
262 Sparc running the Linux-based GNU system.
263 Embedded Sparc processors running the ELF object file format.
268 -malign-functions=xxx
269 -mimpure-text and -mno-impure-text
271 Options -mno-v8 and -mno-sparclite are no longer supported on SPARC
272 targets. Options -mcypress, -mv8, -msupersparc, -msparclite, -mf930,
273 and -mf934 are deprecated and will be deleted in GCC 2.9. Use
276 New features for rs6000 and PowerPC systems:
278 Solaris 2.51 running on PowerPC's.
279 The Linux-based GNU system running on PowerPC's.
280 -mcpu=604e,602,603e,620,801,823,mpc505,821,860,power2
282 -mrelocatable-lib, -mno-relocatable-lib
284 -mupdate, -mno-update
285 -mfused-madd, -mno-fused-madd
289 -mcall-linux, -mcall-solaris, -mcall-sysv-eabi, -mcall-sysv-noeabi
290 -msdata, -msdata=none, -msdata=default, -msdata=sysv, -msdata=eabi
293 wchar_t is now of type long as per the ABI, not unsigned short.
295 -mcpu=403 now implies -mstrict-align.
296 Implement System V profiling.
298 Aix 4.1 GCC targets now default to -mcpu=common so that programs
299 compiled can be moved between rs6000 and powerpc based systems. A
300 consequence of this is that -static won't work, and that some programs
301 may be slightly slower.
303 You can select the default value to use for -mcpu=xxx on rs6000 and
304 powerpc targets by using the --with-cpu=xxx option when configuring the
305 compiler. In addition, a new options, -mtune=xxx was added that
306 selects the machine to schedule for but does not select the
309 Directory names used for storing the multilib libraries on System V
310 and embedded PowerPC systems have been shortened to work with commands
311 like tar that have fixed limits on pathname size.
313 New features for the Hitachi H8/300(H):
316 -ms (for the Hitachi H8/S processor)
319 New features for the ARM:
321 -march=xxx, -mtune=xxx, -mcpu=xxx
322 Support interworking with Thumb code.
323 ARM processor with a.out object format, COFF, or AOF assembler.
324 ARM on "semi-hosted" platform.
326 ARM running the Linux-based GNU system.
328 New feature for Solaris systems:
330 GCC installation no longer makes a copy of system include files,
331 thus insulating GCC better from updates to the operating system.
334 Noteworthy changes in GCC version 2.7.2
335 ---------------------------------------
337 A few bugs have been fixed (most notably the generation of an
338 invalid assembler opcode on some RS/6000 systems).
340 Noteworthy changes in GCC version 2.7.1
341 ---------------------------------------
343 This release fixes numerous bugs (mostly minor) in GCC 2.7.0, but
344 also contains a few new features, mostly related to specific targets.
346 Major changes have been made in code to support Windows NT.
348 The following new targets are supported:
352 HP/UX version 10 on HP PA RISC (treated like version 9)
353 DEC Alpha running Windows NT
355 When parsing C, GCC now recognizes C++ style `//' comments unless you
356 specify `-ansi' or `-traditional'.
358 The PowerPC System V targets (powerpc-*-sysv, powerpc-*-eabi) now use the
359 calling sequence specified in the System V Application Binary Interface
360 Processor Supplement (PowerPC Processor ABI Supplement) rather than the calling
361 sequence used in GCC version 2.7.0. That calling sequence was based on the AIX
362 calling sequence without function descriptors. To compile code for that older
363 calling sequence, either configure the compiler for powerpc-*-eabiaix or use
364 the -mcall-aix switch when compiling and linking.
366 Noteworthy changes in GCC version 2.7.0
367 ---------------------------------------
369 GCC now works better on systems that use ".obj" and ".exe" instead of
370 ".o" and no extension. This involved changes to the driver program,
371 gcc.c, to convert ".o" names to ".obj" and to GCC's Makefile to use
372 ".obj" and ".exe" in filenames that are not targets. In order to
373 build GCC on such systems, you may need versions of GNU make and/or
374 compatible shells. At this point, this support is preliminary.
376 Object file extensions of ".obj" and executable file extensions of
377 ".exe" are allowed when using appropriate version of GNU Make.
379 Numerous enhancements were made to the __attribute__ facility including
380 more attributes and more places that support it. We now support the
381 "packed", "nocommon", "noreturn", "volatile", "const", "unused",
382 "transparent_union", "constructor", "destructor", "mode", "section",
383 "align", "format", "weak", and "alias" attributes. Each of these
384 names may also be specified with added underscores, e.g., "__packed__".
385 __attribute__ may now be applied to parameter definitions, function
386 definitions, and structure, enum, and union definitions.
388 GCC now supports returning more structures in registers, as specified by
389 many calling sequences (ABIs), such as on the HP PA RISC.
391 A new option '-fpack-struct' was added to automatically pack all structure
392 members together without holes.
394 There is a new library (cpplib) and program (cppmain) that at some
395 point will replace cpp (aka cccp). To use cppmain as cpp now, pass
396 the option CCCP=cppmain to make. The library is already used by the
397 fix-header program, which should speed up the fixproto script.
399 New options for supported targets:
402 NetBSD on MIPS, m68k, VAX, and x86.
403 LynxOS on x86, m68k, Sparc, and RS/6000.
404 VxWorks on many targets.
406 Windows/NT on x86 architecture. Initial support for Windows/NT on Alpha
409 Many embedded targets, specifically UDI on a29k, aout, coff, elf,
410 and vsta "operating systems" on m68k, m88k, mips, sparc, and x86.
412 Additional support for x86 (i386, i486, and Pentium):
414 Work with old and new linkers for Linux-based GNU systems,
415 supporting both a.out and ELF.
418 -malign-double, -mregparm=, -malign-loops= and -malign-jumps= switches.
419 On ISC systems, support -Xp like -posix.
421 Additions for RS/6000:
423 Instruction scheduling information for PowerPC 403.
425 -mstring and -mno-string.
426 -msoft-float and floating-point emulation included.
427 Preliminary support for PowerPC System V.4 with or without the GNU as.
428 Preliminary support for EABI.
429 Preliminary support for 64-bit systems.
430 Both big and little endian systems.
432 New features for MIPS-based systems:
438 Allow dollar signs in labels on SGI/Irix 5.x.
440 New support for HP PA RISC:
442 Generation of PIC (requires binutils-2.5.2.u6 or later).
443 HP-UX version 9 on HP PA RISC (dynamically links even with -g).
444 Processor variants for HP PA RISC: 700, 7100, and 7100LC.
445 Automatic generation of long calls when needed.
446 -mfast-indirect-calls for kernels and static binaries.
448 The called routine now copies arguments passed by invisible reference,
449 as required by the calling standard.
451 Other new miscellaneous target-specific support:
454 -mold-align for i960.
455 Configuration for "semi-hosted" ARM.
456 -momit-leaf-frame-pointer for M88k.
457 SH3 variant of Hitachi Super-H and support both big and little endian.
459 Changes to Objective-C:
461 Bare-bones implementation of NXConstantString has been added,
462 which is invoked by the @"string" directive.
464 Class * has been changed to Class to conform to the NextSTEP and
467 Enhancements to make dynamic loading easier.
469 The module version number has been updated to Version 7, thus existing
470 code will need to be recompiled to use the current run-time library.
472 GCC now supports the ISO Normative Addendum 1 to the C Standard.
475 The header <iso646.h> defines macros for C programs written
476 in national variants of ISO 646.
478 The following digraph tokens are supported:
480 These behave like the following, respectively:
483 Digraph tokens are supported unless you specify the `-traditional'
484 option; you do not need to specify `-ansi' or `-trigraphs'. Except
485 for contrived and unlikely examples involving preprocessor
486 stringizing, digraph interpretation doesn't change the meaning of
487 programs; this is unlike trigraph interpretation, which changes the
488 meanings of relatively common strings.
490 The macro __STDC_VERSION__ has the value 199409L.
492 As usual, for full conformance to the standard, you also need a
493 C library that conforms.
495 The following lists changes that have been made to g++. If some
496 features mentioned below sound unfamiliar, you will probably want to
497 look at the recently-released public review copy of the C++ Working
498 Paper. For PostScript and PDF (Adobe Acrobat) versions, see the
499 archive at ftp://research.att.com/dist/stdc++/WP. For HTML and ASCII
500 versions, see ftp://ftp.cygnus.com/pub/g++. On the web, see
501 http://www.cygnus.com/~mrs/wp-draft.
503 The scope of variables declared in the for-init-statement has been changed
504 to conform to http://www.cygnus.com/~mrs/wp-draft/stmt.html#stmt.for; as a
505 result, packages such as groff 1.09 will not compile unless you specify the
506 -fno-for-scope flag. PLEASE DO NOT REPORT THIS AS A BUG; this is a change
507 mandated by the C++ standardization committee.
509 Binary incompatibilities:
511 The builtin 'bool' type is now the size of a machine word on RISC targets,
512 for code efficiency; it remains one byte long on CISC targets.
514 Code that does not use #pragma interface/implementation will most
515 likely shrink dramatically, as g++ now only emits the vtable for a
516 class in the translation unit where its first non-inline, non-abstract
517 virtual function is defined.
519 Classes that do not define the copy constructor will sometimes be
520 passed and returned in registers. This may illuminate latent bugs in
523 Support for automatic template instantiation has *NOT* been added, due
524 to a disagreement over design philosophies.
526 Support for exception handling has been improved; more targets are now
527 supported, and throws will use the RTTI mechanism to match against the
528 catch parameter type. Optimization is NOT SUPPORTED with
529 -fhandle-exceptions; no need to report this as a bug.
531 Support for Run-Time Type Identification has been added with -frtti.
532 This support is still in alpha; one major restriction is that any file
533 compiled with -frtti must include <typeinfo.h>.
535 Preliminary support for namespaces has been added. This support is far
536 from complete, and probably not useful.
538 Synthesis of compiler-generated constructors, destructors and
539 assignment operators is now deferred until the functions are used.
541 The parsing of expressions such as `a ? b : c = 1' has changed from
542 `(a ? b : c) = 1' to `a : b ? (c = 1)'.
544 The code generated for testing conditions, especially those using ||
545 and &&, is now more efficient.
547 The operator keywords and, and_eq, bitand, bitor, compl, not, not_eq,
548 or, or_eq, xor and xor_eq are now supported. Use -ansi or
549 -foperator-names to enable them.
551 The 'explicit' keyword is now supported. 'explicit' is used to mark
552 constructors and type conversion operators that should not be used
555 g++ now accepts the typename keyword, though it currently has no
556 semantics; it can be a no-op in the current template implementation.
557 You may want to start using it in your code, however, since the
558 pending rewrite of the template implementation to compile STL properly
559 (perhaps for 2.8.0, perhaps not) will require you to use it as
560 indicated by the current draft.
562 Handling of user-defined type conversion has been overhauled so that
563 type conversion operators are now found and used properly in
564 expressions and function calls.
566 -fno-strict-prototype now only applies to function declarations with
569 g++ now warns about 'if (x=0)' with -Wparentheses or -Wall.
571 #pragma weak and #pragma pack are supported on System V R4 targets, as
572 are various other target-specific #pragmas supported by gcc.
574 new and delete of const types is now allowed (with no additional
577 Explicit instantiation of template methods is now supported. Also,
578 'inline template class foo<int>;' can be used to emit only the vtable
579 for a template class.
581 With -fcheck-new, g++ will check the return value of all calls to
582 operator new, and not attempt to modify a returned null pointer.
584 The template instantiation code now handles more conversions when
585 passing to a parameter that does not depend on template arguments.
586 This means that code like 'string s; cout << s;' now works.
588 Invalid jumps in a switch statement past declarations that require
589 initializations are now caught.
591 Functions declared 'extern inline' now have the same linkage semantics
592 as inline member functions. On supported targets, where previously
593 these functions (and vtables, and template instantiations) would have
594 been defined statically, they will now be defined as weak symbols so
595 that only one out-of-line definition is used.
597 collect2 now demangles linker output, and c++filt has become part of
598 the gcc distribution.
600 Noteworthy changes in GCC version 2.6.3:
602 A few more bugs have been fixed.
604 Noteworthy changes in GCC version 2.6.2:
606 A few bugs have been fixed.
608 Names of attributes can now be preceded and followed by double underscores.
610 Noteworthy changes in GCC version 2.6.1:
612 Numerous (mostly minor) bugs have been fixed.
614 The following new configurations are supported:
616 GNU on x86 (instead of treating it like MACH)
617 NetBSD on Sparc and Motorola 68k
618 AIX 4.1 on RS/6000 and PowerPC systems
619 Sequent DYNIX/ptx 1.x and 2.x.
620 Both COFF and ELF configurations on AViiON without using /bin/gcc
621 Windows/NT on x86 architecture; preliminary
622 AT&T DSP1610 digital signal processor chips
623 i960 systems on bare boards using COFF
624 PDP11; target only and not extensively tested
626 The -pg option is now supported for Alpha under OSF/1 V3.0 or later.
628 Files with an extension of ".c++" are treated as C++ code.
630 The -Xlinker and -Wl arguments are now passed to the linker in the
631 position they were specified on the command line. This makes it
632 possible, for example, to pass flags to the linker about specific
635 The use of positional arguments to the configure script is no longer
636 recommended. Use --target= to specify the target; see the GCC manual.
638 The 386 now supports two new switches: -mreg-alloc=<string> changes
639 the default register allocation order used by the compiler, and
640 -mno-wide-multiply disables the use of the mul/imul instructions that
641 produce 64 bit results in EAX:EDX from 32 bit operands to do long long
642 multiplies and 32-bit division by constants.
644 Noteworthy changes in GCC version 2.6.0:
646 Numerous bugs have been fixed, in the C and C++ front-ends, as
647 well as in the common compiler code.
649 This release includes the C, Objective-C, and C++ compilers. However,
650 we have moved the files for the C++ compiler (G++) files to a
651 subdirectory, cp. Subsequent releases of GCC will split these files
652 to a separate TAR file.
654 The G++ team has been tracking the development of the ANSI standard for C++.
655 Here are some new features added from the latest working paper:
657 * built-in boolean type 'bool', with constants 'true' and 'false'.
658 * array new and delete (operator new [] and delete []).
659 * WP-conforming lifetime of temporaries.
660 * explicit instantiation of templates (template class A<int>;),
661 along with an option (-fno-implicit-templates) to disable emission
662 of implicitly instantiated templates, obsoletes -fexternal-templates.
663 * static member constants (static const int foo = 4; within the
666 Many error messages have been improved to tell the user more about the
667 problem. Conformance checking with -pedantic-errors has been
668 improved. G++ now compiles Fresco.
670 There is now an experimental implementation of virtual functions using
671 thunks instead of Cfront-style vtables, enabled with -fvtable-thunks.
672 This option also enables a heuristic which causes the compiler to only
673 emit the vtable in the translation unit where its first non-inline
674 virtual function is defined; using this option and
675 -fno-implicit-templates, users should be able to avoid #pragma
676 interface/implementation altogether.
678 Signatures have been added as a GNU C++ extension. Using the option
679 -fhandle-signatures, users are able to turn on recognition of
680 signatures. A short introduction on signatures is in the section
681 `Extension to the C++ Language' in the manual.
683 The `g++' program is now a C program, rather than a shell script.
685 Lots and lots and lots of bugs fixes, in nested types, access control,
686 pointers to member functions, the parser, templates, overload
687 resolution, etc, etc.
689 There have been two major enhancements to the Objective-C compiler:
691 1) Added portability. It now runs on Alpha, and some problems with
692 message forwarding have been addressed on other platforms.
694 2) Selectors have been redefined to be pointers to structs like:
695 { void *sel_id, char *sel_types }, where the sel_id is the unique
696 identifier, the selector itself is no longer unique.
698 Programmers should use the new function sel_eq to test selector
701 The following major changes have been made to the base compiler and
702 machine-specific files.
704 - The MIL-STD-1750A is a new port, but still preliminary.
706 - The h8/300h is now supported; both the h8/300 and h8/300h ports come
707 with 32 bit IEEE 754 software floating point support.
709 - The 64-bit Sparc (v9) and 64-bit MIPS chips are supported.
711 - NetBSD is supported on m68k, Intel x86, and pc523 systems and FreeBSD
714 - COFF is supported on x86, m68k, and Sparc systems running LynxOS.
716 - 68K systems from Bull and Concurrent are supported and System V
717 Release 4 is supported on the Atari.
719 - GCC supports GAS on the Motorola 3300 (sysV68) and debugging
720 (assuming GAS) on the Plexus 68K system. (However, GAS does not yet
721 work on those systems).
723 - System V Release 4 is supported on MIPS (Tandem).
725 - For DG/UX, an ELF configuration is now supported, and both the ELF
726 and BCS configurations support ELF and COFF object file formats.
728 - OSF/1 V2.0 is supported on Alpha.
730 - Function profiling is also supported on Alpha.
732 - GAS and GDB is supported for Irix 5 (MIPS).
734 - "common mode" (code that will run on both POWER and PowerPC
735 architectures) is now supported for the RS/6000 family; the
736 compiler knows about more PPC chips.
738 - Both NeXTStep 2.1 and 3 are supported on 68k-based architectures.
740 - On the AMD 29k, the -msoft-float is now supported, as well as
741 -mno-sum-in-toc for RS/6000, -mapp-regs and -mflat for Sparc, and
742 -membedded-pic for MIPS.
744 - GCC can now convert division by integer constants into the equivalent
745 multiplication and shift operations when that is faster than the
748 - Two new warning options, -Wbad-function-cast and
749 -Wmissing-declarations have been added.
751 - Configurations may now add machine-specific __attribute__ options on
752 type; many machines support the `section' attribute.
754 - The -ffast-math flag permits some optimization that violate strict
755 IEEE rules, such as converting X * 0.0 to 0.0.
757 Noteworthy changes in GCC version 2.5.8:
759 This release only fixes a few serious bugs. These include fixes for a
760 bug that prevented most programs from working on the RS/6000, a bug
761 that caused invalid assembler code for programs with a `switch'
762 statement on the NS32K, a G++ problem that caused undefined names in
763 some configurations, and several less serious problems, some of which
764 can affect most configuration.
766 Noteworthy change in GCC version 2.5.7:
768 This release only fixes a few bugs, one of which was causing bootstrap
769 compare errors on some systems.
771 Noteworthy change in GCC version 2.5.6:
773 A few backend bugs have been fixed, some of which only occur on one
776 The C++ compiler in 2.5.6 includes:
778 * fixes for some common crashes
779 * correct handling of nested types that are referenced as `foo::bar'
780 * spurious warnings about friends being declared static and never
781 defined should no longer appear
782 * enums that are local to a method in a class, or a class that's
783 local to a function, are now handled correctly. For example:
784 class foo { void bar () { enum { x, y } E; x; } };
785 void bar () { class foo { enum { x, y } E; E baz; }; }
787 Noteworthy change in GCC version 2.5.5:
789 A large number of C++ bugs have been fixed.
791 The fixproto script adds prototypes conditionally on __cplusplus.
793 Noteworthy change in GCC version 2.5.4:
795 A bug fix in passing of structure arguments for the HP-PA architecture
796 makes code compiled with GCC 2.5.4 incompatible with code compiled
797 with earlier versions (if it passes struct arguments of 33 to 64 bits,
798 interspersed with other types of arguments).
800 Noteworthy change in gcc version 2.5.3:
802 The method of "mangling" C++ function names has been changed. So you
803 must recompile all C++ programs completely when you start using GCC
804 2.5. Also, GCC 2.5 requires libg++ version 2.5. Earlier libg++
805 versions won't work with GCC 2.5. (This is generally true--GCC
806 version M.N requires libg++ version M.N.)
808 Noteworthy GCC changes in version 2.5:
810 * There is now support for the IBM 370 architecture as a target.
811 Currently the only operating system supported is MVS; GCC does not run
812 on MVS, so you must produce .s files using GCC as a cross compiler,
813 then transfer them to MVS to assemble them. This port is not reliable
816 * The Power PC is now supported.
818 * The i860-based Paragon machine is now supported.
820 * The Hitachi 3050 (an HP-PA machine) is now supported.
822 * The variable __GNUC_MINOR__ holds the minor version number of GCC, as
823 an integer. For version 2.5.X, the value is 5.
825 * In C, initializers for static and global variables are now processed
826 an element at a time, so that they don't need a lot of storage.
828 * The C syntax for specifying which structure field comes next in an
829 initializer is now `.FIELDNAME='. The corresponding syntax for
830 array initializers is now `[INDEX]='. For example,
833 = { [' '] = 1, ['\t'] = 1, ['\n'] = 1 };
835 This was changed to accord with the syntax proposed by the Numerical
836 C Extensions Group (NCEG).
838 * Complex numbers are now supported in C. Use the keyword __complex__
839 to declare complex data types. See the manual for details.
841 * GCC now supports `long double' meaningfully on the Sparc (128-bit
842 floating point) and on the 386 (96-bit floating point). The Sparc
843 support is enabled on Solaris 2.x because earlier system versions
844 (SunOS 4) have bugs in the emulation.
846 * All targets now have assertions for cpu, machine and system. So you
847 can now use assertions to distinguish among all supported targets.
849 * Nested functions in C may now be inline. Just declare them inline
852 * Packed structure members are now supported fully; it should be possible
853 to access them on any supported target, no matter how little alignment
856 * To declare that a function does not return, you must now write
857 something like this (works only in 2.5):
859 void fatal () __attribute__ ((noreturn));
861 or like this (works in older versions too):
863 typedef void voidfn ();
865 volatile voidfn fatal;
867 It used to be possible to do so by writing this:
869 volatile void fatal ();
871 but it turns out that ANSI C requires that to mean something
872 else (which is useless).
874 Likewise, to declare that a function is side-effect-free
875 so that calls may be deleted or combined, write
876 something like this (works only in 2.5):
878 int computation () __attribute__ ((const));
880 or like this (works in older versions too):
882 typedef int intfn ();
884 const intfn computation;
886 * The new option -iwithprefixbefore specifies a directory to add to
887 the search path for include files in the same position where -I would
888 put it, but uses the specified prefix just like -iwithprefix.
890 * Basic block profiling has been enhanced to record the function the
891 basic block comes from, and if the module was compiled for debugging,
892 the line number and filename. A default version of the basic block
893 support module has been added to libgcc2 that appends the basic block
894 information to a text file 'bb.out'. Machine descriptions can now
895 override the basic block support module in the target macro file.
899 * The new flag `-fansi-overloading' for C++. Use a newly implemented
900 scheme of argument matching for C++. It makes g++ more accurately
901 obey the rules set down in Chapter 13 of the Annotated C++ Reference
902 Manual (the ARM). This option will be turned on by default in a
905 * The -finline-debug flag is now gone (it was never really used by the
908 * Recognizing the syntax for pointers to members, e.g., "foo::*bar", has been
909 dramatically improved. You should not get any syntax errors or incorrect
910 runtime results while using pointers to members correctly; if you do, it's
913 * Forward declaration of an enum is now flagged as an error.
915 * Class-local typedefs are now working properly.
917 * Nested class support has been significantly improved. The compiler
918 will now (in theory) support up to 240 nested classes before hitting
919 other system limits (like memory size).
921 * There is a new C version of the `g++' driver, to replace the old
922 shell script. This should significantly improve the performance of
923 executing g++ on a system where a user's PATH environment variable
924 references many NFS-mounted filesystems. This driver also works
925 under MS-DOS and OS/2.
927 * The ANSI committee working on the C++ standard has adopted a new
928 keyword `mutable'. This will allow you to make a specific member be
929 modifiable in an otherwise const class.
931 Noteworthy GCC changes in version 2.4.4:
933 A crash building g++ on various hosts (including m68k) has been
934 fixed. Also the g++ compiler no longer reports incorrect
935 ambiguities in some situations where they do not exist, and
936 const template member functions are now being found properly.
938 Noteworthy GCC changes in version 2.4:
940 * On each target, the default is now to return short structures
941 compatibly with the "usual" compiler on that target.
943 For most targets, this means the default is to return all structures
944 in memory, like long structures, in whatever way is used on that
945 target. Use -freg-struct-return to enable returning short structures
946 (and unions) in registers.
948 This change means that newly compiled binaries are incompatible with
949 binaries compiled with previous versions of GCC.
951 On some targets, GCC is itself the usual compiler. On these targets,
952 the default way to return short structures is still in registers.
953 Use -fpcc-struct-return to tell GCC to return them in memory.
955 * There is now a floating point emulator which can imitate the way all
956 supported target machines do floating point arithmetic.
958 This makes it possible to have cross compilation to and from the VAX,
959 and between machines of different endianness. However, this works
960 only when the target machine description is updated to use the new
961 facilities, and not all have been updated.
963 This also makes possible support for longer floating point types.
964 GCC 2.4 supports extended format on the 68K if you use `long double',
965 for targets that have a 68881. (When we have run time library
966 routines for extended floating point, then `long double' will use
967 extended format on all 68K targets.)
969 We expect to support extended floating point on the i386 and Sparc in
972 * Building GCC now automatically fixes the system's header files.
973 This should require no attention.
975 * GCC now installs an unsigned data type as size_t when it fixes the
976 header files (on all but a handful of old target machines).
977 Therefore, the bug that size_t failed to be unsigned is fixed.
979 * Building and installation are now completely separate.
980 All new files are constructed during the build process;
981 installation just copies them.
983 * New targets supported: Clipper, Hitachi SH, Hitachi 8300, and Sparc
986 * A totally new and much better Objective C run time system is included.
988 * Objective C supports many new features. Alas, I can't describe them
989 since I don't use that language; however, they are the same ones
990 supported in recent versions of the NeXT operating system.
992 * The builtin functions __builtin_apply_args, __builtin_apply and
993 __builtin_return let you record the arguments and returned
994 value of a function without knowing their number or type.
996 * The builtin string variables __FUNCTION__ and __PRETTY_FUNCTION__
997 give the name of the function in the source, and a pretty-printed
998 version of the name. The two are the same in C, but differ in C++.
1000 * Casts to union types do not yield lvalues.
1002 * ## before an empty rest argument discards the preceding sequence
1003 of non-whitespace characters from the macro definition.
1004 (This feature is subject to change.)
1007 New features specific to C++:
1009 * The manual contains a new section ``Common Misunderstandings with
1010 GNU C++'' that C++ users should read.
1012 * #pragma interface and #pragma implementation let you use the same
1013 C++ source file for both interface and implementation.
1014 However, this mechanism is still in transition.
1016 * Named returned values let you avoid an extra constructor call
1017 when a function result has a class type.
1019 * The C++ operators <? and >? yield min and max, respectively.
1021 * C++ gotos can exit a block safely even if the block has
1022 aggregates that require destructors.
1024 * gcc defines the macro __GNUG__ when compiling C++ programs.
1026 * GNU C++ now correctly distinguishes between the prefix and postfix
1027 forms of overloaded operator ++ and --. To avoid breaking old
1028 code, if a class defines only the prefix form, the compiler
1029 accepts either ++obj or obj++, unless -pedantic is used.
1031 * If you are using version 2.3 of libg++, you need to rebuild it with
1032 `make CC=gcc' to avoid mismatches in the definition of `size_t'.
1034 Newly documented compiler options:
1037 Omit the standard system startup files when linking.
1040 Consider memory references to extern and global data items to
1044 Add DIR to the second include path.
1047 Specify PREFIX for later -iwithprefix options.
1050 Add PREFIX/DIR to the second include path.
1053 Emit Sparc v8 code (with integer multiply and divide).
1055 Emit Sparclite code (roughly v7.5).
1057 -print-libgcc-file-name
1058 Search for the libgcc.a file, print its absolute file name, and exit.
1060 -Woverloaded-virtual
1061 Warn when a derived class function declaration may be an error
1062 in defining a C++ virtual function.
1064 -Wtemplate-debugging
1065 When using templates in a C++ program, warn if debugging is
1066 not yet fully available.
1069 Control how C++ virtual function definitions are used
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