Using and Porting GNU CC

Richard M. Stallman

last updated 22 May 1992

for version 2.2

(preliminary draft, which will change)

Copyright © 1988, 1989, 1992 Free Software Foundation, Inc.

Permission is granted to make and distribute verbatim copies of this manual provided the copyright notice and this permission notice are preserved on all copies.

Permission is granted to copy and distribute modified versions of this manual under the conditions for verbatim copying, provided also that the sections entitled “GNU General Public License” and “Boycott” are included exactly as in the original, and provided that the entire resulting derived work is distributed under the terms of a permission notice identical to this one.

Permission is granted to copy and distribute translations of this manual into another language, under the above conditions for modified versions, except that the sections entitled “GNU General Public License” and “Boycott”, and this permission notice, may be included in translations approved by the Free Software Foundation instead of in the original English.

GNU GENERAL PUBLIC LICENSE

Version 2, June 1991

Copyright © 1989, 1991 Free Software Foundation, Inc.
675 Mass Ave, Cambridge, MA 02139, USA

Everyone is permitted to copy and distribute verbatim copies
of this license document, but changing it is not allowed.

Preamble

The licenses for most software are designed to take away your freedom to share and change it. By contrast, the GNU General Public License is intended to guarantee your freedom to share and change free software—to make sure the software is free for all its users. This General Public License applies to most of the Free Software Foundation’s software and to any other program whose authors commit to using it. (Some other Free Software Foundation software is covered by the GNU Library General Public License instead.) You can apply it to your programs, too.

When we speak of free software, we are referring to freedom, not price. Our General Public Licenses are designed to make sure that you have the freedom to distribute copies of free software (and charge for this service if you wish), that you receive source code or can get it if you want it, that you can change the software or use pieces of it in new free programs; and that you know you can do these things.

To protect your rights, we need to make restrictions that forbid anyone to deny you these rights or to ask you to surrender the rights. These restrictions translate to certain responsibilities for you if you distribute copies of the software, or if you modify it.

For example, if you distribute copies of such a program, whether gratis or for a fee, you must give the recipients all the rights that you have. You must make sure that they, too, receive or can get the source code. And you must show them these terms so they know their rights.

We protect your rights with two steps: (1) copyright the software, and (2) offer you this license which gives you legal permission to copy, distribute and/or modify the software.

Also, for each author’s protection and ours, we want to make certain that everyone understands that there is no warranty for this free software. If the software is modified by someone else and passed on, we want its recipients to know that what they have is not the original, so that any problems introduced by others will not reflect on the original authors’ reputations.

Finally, any free program is threatened constantly by software patents. We wish to avoid the danger that redistributors of a free program will individually obtain patent licenses, in effect making the program proprietary. To prevent this, we have made it clear that any patent must be licensed for everyone’s free use or not licensed at all.

The precise terms and conditions for copying, distribution and modification follow.

1. This License applies to any program or other work which contains a notice placed by the copyright holder saying it may be distributed under the terms of this General Public License. The “Program”, below, refers to any such program or work, and a “work based on the Program” means either the Program or any derivative work under copyright law: that is to say, a work containing the Program or a portion of it, either verbatim or with modifications and/or translated into another language. (Hereinafter, translation is included without limitation in the term “modification”.) Each licensee is addressed as “you”.

   Activities other than copying, distribution and modification are not covered by this License; they are outside its scope. The act of running the Program is not restricted, and the output from the Program is covered only if its contents constitute a work based on the Program (independent of having been made by running the Program). Whether that is true depends on what the Program does.

2. You may copy and distribute verbatim copies of the Program’s source code as you receive it, in any medium, provided that you conspicuously and appropriately publish on each copy an appropriate copyright notice and disclaimer of warranty; keep intact all the notices that refer to this License and to the absence of any warranty; and give any other recipients of the Program a copy of this License along with the Program.

   You may charge a fee for the physical act of transferring a copy, and you may at your option offer warranty protection in exchange for a fee.

3. You may modify your copy or copies of the Program or any portion of it, thus forming a work based on the Program, and copy and distribute such modifications or work under the terms of Section 1 above, provided that you also meet all of these conditions:
   1. You must cause the modified files to carry prominent notices stating that you changed the files and the date of any change.
   2. You must cause any work that you distribute or publish, that in whole or in part contains or is derived from the Program or any part thereof, to be licensed as a whole at no charge to all third parties under the terms of this License.
   3. If the modified program normally reads commands interactively when run, you must cause it, when started running for such interactive use in the most ordinary way, to print or display an announcement including an appropriate copyright notice and a notice that there is no warranty (or else, saying that you provide a warranty) and that users may redistribute the program under these conditions, and telling the user how to view a copy of this License. (Exception: if the Program itself is interactive but does not normally print such an announcement, your work based on the Program is not required to print an announcement.)

   These requirements apply to the modified work as a whole. If identifiable sections of that work are not derived from the Program, and can be reasonably considered independent and separate works in themselves, then this License, and its terms, do not apply to those sections when you distribute them as separate works. But when you distribute the same sections as part of a whole which is a work based on the Program, the distribution of the whole must be on the terms of this License, whose permissions for other licensees extend to the entire whole, and thus to each and every part regardless of who wrote it.

   Thus, it is not the intent of this section to claim rights or contest your rights to work written entirely by you; rather, the intent is to exercise the right to control the distribution of derivative or collective works based on the Program.

   In addition, mere aggregation of another work not based on the Program with the Program (or with a work based on the Program) on a volume of a storage or distribution medium does not bring the other work under the scope of this License.

4. You may copy and distribute the Program (or a work based on it, under Section 2) in object code or executable form under the terms of Sections 1 and 2 above provided that you also do one of the following:
   1. Accompany it with the complete corresponding machine-readable source code, which must be distributed under the terms of Sections 1 and 2 above on a medium customarily used for software interchange; or,
   2. Accompany it with a written offer, valid for at least three years, to give any third party, for a charge no more than your cost of physically performing source distribution, a complete machine-readable copy of the corresponding source code, to be distributed under the terms of Sections 1 and 2 above on a medium customarily used for software interchange; or,
   3. Accompany it with the information you received as to the offer to distribute corresponding source code. (This alternative is allowed only for noncommercial distribution and only if you received the program in object code or executable form with such an offer, in accord with Subsection b above.)

   The source code for a work means the preferred form of the work for making modifications to it. For an executable work, complete source code means all the source code for all modules it contains, plus any associated interface definition files, plus the scripts used to control compilation and installation of the executable. However, as a special exception, the source code distributed need not include anything that is normally distributed (in either source or binary form) with the major components (compiler, kernel, and so on) of the operating system on which the executable runs, unless that component itself accompanies the executable.

   If distribution of executable or object code is made by offering access to copy from a designated place, then offering equivalent access to copy the source code from the same place counts as distribution of the source code, even though third parties are not compelled to copy the source along with the object code.

5. You may not copy, modify, sublicense, or distribute the Program except as expressly provided under this License. Any attempt otherwise to copy, modify, sublicense or distribute the Program is void, and will automatically terminate your rights under this License. However, parties who have received copies, or rights, from you under this License will not have their licenses terminated so long as such parties remain in full compliance.
6. You are not required to accept this License, since you have not signed it. However, nothing else grants you permission to modify or distribute the Program or its derivative works. These actions are prohibited by law if you do not accept this License. Therefore, by modifying or distributing the Program (or any work based on the Program), you indicate your acceptance of this License to do so, and all its terms and conditions for copying, distributing or modifying the Program or works based on it.
7. Each time you redistribute the Program (or any work based on the Program), the recipient automatically receives a license from the original licensor to copy, distribute or modify the Program subject to these terms and conditions. You may not impose any further restrictions on the recipients’ exercise of the rights granted herein. You are not responsible for enforcing compliance by third parties to this License.
8. If, as a consequence of a court judgment or allegation of patent infringement or for any other reason (not limited to patent issues), conditions are imposed on you (whether by court order, agreement or otherwise) that contradict the conditions of this License, they do not excuse you from the conditions of this License. If you cannot distribute so as to satisfy simultaneously your obligations under this License and any other pertinent obligations, then as a consequence you may not distribute the Program at all. For example, if a patent license would not permit royalty-free redistribution of the Program by all those who receive copies directly or indirectly through you, then the only way you could satisfy both it and this License would be to refrain entirely from distribution of the Program.

   If any portion of this section is held invalid or unenforceable under any particular circumstance, the balance of the section is intended to apply and the section as a whole is intended to apply in other circumstances.

   It is not the purpose of this section to induce you to infringe any patents or other property right claims or to contest validity of any such claims; this section has the sole purpose of protecting the integrity of the free software distribution system, which is implemented by public license practices. Many people have made generous contributions to the wide range of software distributed through that system in reliance on consistent application of that system; it is up to the author/donor to decide if he or she is willing to distribute software through any other system and a licensee cannot impose that choice.

   This section is intended to make thoroughly clear what is believed to be a consequence of the rest of this License.

9. If the distribution and/or use of the Program is restricted in certain countries either by patents or by copyrighted interfaces, the original copyright holder who places the Program under this License may add an explicit geographical distribution limitation excluding those countries, so that distribution is permitted only in or among countries not thus excluded. In such case, this License incorporates the limitation as if written in the body of this License.
10. The Free Software Foundation may publish revised and/or new versions of the General Public License from time to time. Such new versions will be similar in spirit to the present version, but may differ in detail to address new problems or concerns.

    Each version is given a distinguishing version number. If the Program specifies a version number of this License which applies to it and “any later version”, you have the option of following the terms and conditions either of that version or of any later version published by the Free Software Foundation. If the Program does not specify a version number of this License, you may choose any version ever published by the Free Software Foundation.

11. If you wish to incorporate parts of the Program into other free programs whose distribution conditions are different, write to the author to ask for permission. For software which is copyrighted by the Free Software Foundation, write to the Free Software Foundation; we sometimes make exceptions for this. Our decision will be guided by the two goals of preserving the free status of all derivatives of our free software and of promoting the sharing and reuse of software generally.
12. BECAUSE THE PROGRAM IS LICENSED FREE OF CHARGE, THERE IS NO WARRANTY FOR THE PROGRAM, TO THE EXTENT PERMITTED BY APPLICABLE LAW. EXCEPT WHEN OTHERWISE STATED IN WRITING THE COPYRIGHT HOLDERS AND/OR OTHER PARTIES PROVIDE THE PROGRAM “AS IS” WITHOUT WARRANTY OF ANY KIND, EITHER EXPRESSED OR IMPLIED, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE. THE ENTIRE RISK AS TO THE QUALITY AND PERFORMANCE OF THE PROGRAM IS WITH YOU. SHOULD THE PROGRAM PROVE DEFECTIVE, YOU ASSUME THE COST OF ALL NECESSARY SERVICING, REPAIR OR CORRECTION.
13. IN NO EVENT UNLESS REQUIRED BY APPLICABLE LAW OR AGREED TO IN WRITING WILL ANY COPYRIGHT HOLDER, OR ANY OTHER PARTY WHO MAY MODIFY AND/OR REDISTRIBUTE THE PROGRAM AS PERMITTED ABOVE, BE LIABLE TO YOU FOR DAMAGES, INCLUDING ANY GENERAL, SPECIAL, INCIDENTAL OR CONSEQUENTIAL DAMAGES ARISING OUT OF THE USE OR INABILITY TO USE THE PROGRAM (INCLUDING BUT NOT LIMITED TO LOSS OF DATA OR DATA BEING RENDERED INACCURATE OR LOSSES SUSTAINED BY YOU OR THIRD PARTIES OR A FAILURE OF THE PROGRAM TO OPERATE WITH ANY OTHER PROGRAMS), EVEN IF SUCH HOLDER OR OTHER PARTY HAS BEEN ADVISED OF THE POSSIBILITY OF SUCH DAMAGES.

Appendix: How to Apply These Terms to Your New Programs

If you develop a new program, and you want it to be of the greatest possible use to the public, the best way to achieve this is to make it free software which everyone can redistribute and change under these terms.

To do so, attach the following notices to the program. It is safest to attach them to the start of each source file to most effectively convey the exclusion of warranty; and each file should have at least the “copyright” line and a pointer to where the full notice is found.

one line to give the program's name and a brief idea of what it does.
Copyright (C) 19yy  name of author

This program is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; either version 2 of the License, or
(at your option) any later version.

This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
GNU General Public License for more details.

You should have received a copy of the GNU General Public License
along with this program; if not, write to the Free Software
Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.

Also add information on how to contact you by electronic and paper mail.

If the program is interactive, make it output a short notice like this when it starts in an interactive mode:

Gnomovision version 69, Copyright (C) 19yy name of author
Gnomovision comes with ABSOLUTELY NO WARRANTY; for details type `show w'.
This is free software, and you are welcome to redistribute it
under certain conditions; type `show c' for details.

The hypothetical commands ‘show w’ and ‘show c’ should show the appropriate parts of the General Public License. Of course, the commands you use may be called something other than ‘show w’ and ‘show c’; they could even be mouse-clicks or menu items—whatever suits your program.

You should also get your employer (if you work as a programmer) or your school, if any, to sign a “copyright disclaimer” for the program, if necessary. Here is a sample; alter the names:

Yoyodyne, Inc., hereby disclaims all copyright interest in the program
`Gnomovision' (which makes passes at compilers) written by James Hacker.

signature of Ty Coon, 1 April 1989
Ty Coon, President of Vice

This General Public License does not permit incorporating your program into proprietary programs. If your program is a subroutine library, you may consider it more useful to permit linking proprietary applications with the library. If this is what you want to do, use the GNU Library General Public License instead of this License.

Contributors to GNU CC

In addition to Richard Stallman, several people have written parts of GNU CC.

• The idea of using RTL and some of the optimization ideas came from the program PO written at the University of Arizona by Jack Davidson and Christopher Fraser. See “Register Allocation and Exhaustive Peephole Optimization”, Software Practice and Experience 14 (9), Sept. 1984, 857-866.
• Paul Rubin wrote most of the preprocessor.
• Leonard Tower wrote parts of the parser, RTL generator, and RTL definitions, and of the Vax machine description.
• Ted Lemon wrote parts of the RTL reader and printer.
• Jim Wilson implemented loop strength reduction and some other loop optimizations.
• Nobuyuki Hikichi of Software Research Associates, Tokyo, contributed the support for the Sony NEWS machine.
• Charles LaBrec contributed the support for the Integrated Solutions 68020 system.
• Michael Tiemann of Cygnus Support wrote the front end for C++, as well as the support for inline functions and instruction scheduling. Also the descriptions of the National Semiconductor 32000 series cpu, the SPARC cpu and part of the Motorola 88000 cpu.
• Jan Stein of the Chalmers Computer Society provided support for Genix, as well as part of the 32000 machine description.
• Randy Smith finished the Sun FPA support.
• Robert Brown implemented the support for Encore 32000 systems.
• David Kashtan of SRI adapted GNU CC to the Vomit-Making System (VMS).
• Alex Crain provided changes for the 3b1.
• Greg Satz and Chris Hanson assisted in making GNU CC work on HP-UX for the 9000 series 300.
• William Schelter did most of the work on the Intel 80386 support.
• Christopher Smith did the port for Convex machines.
• Paul Petersen wrote the machine description for the Alliant FX/8.
• Alain Lichnewsky ported GNU CC to the Mips cpu.
• Devon Bowen, Dale Wiles and Kevin Zachmann ported GNU CC to the Tahoe.
• Jonathan Stone wrote the machine description for the Pyramid computer.
• Gary Miller ported GNU CC to Charles River Data Systems machines.
• Richard Kenner of New York University wrote the machine descriptions for the AMD 29000, the IBM RT PC, and the IBM RS/6000 as well as the support for instruction attributes. He also made changes to better support RISC processors including changes to common subexpression elimination, strength reduction, function calling sequence handling, and condition code support, in addition to generalizing the code for frame pointer elimination.
• Richard Kenner and Michael Tiemann jointly developed reorg.c, the delay slot scheduler.
• Mike Meissner and Tom Wood of Data General finished the port to the Motorola 88000.
• Masanobu Yuhara of Fujitsu Laboratories implemented the machine description for the Tron architecture (specifically, the Gmicro).
• NeXT, Inc. donated the front end that supports the Objective C language.
• James van Artsdalen wrote the code that makes efficient use of the Intel 80387 register stack.
• Mike Meissner at the Open Software Foundation finished the port to the MIPS cpu, including adding ECOFF debug support.
• Ron Guilmette implemented the protoize and unprotoize tools, the support for Dwarf symbolic debugging information, and much of the support for System V Release 4. He has also worked heavily on the Intel 386 and 860 support.
• Torbjorn Granlund of the Swedish Institute of Computer Science implemented multiply-by-constant optimization and better long long support, and improved leaf function register allocation.

1 Protect Your Freedom—Fight “Look And Feel”

This section is a political message from the League for Programming Freedom to the users of GNU CC. It is included here as an expression of support for the League on the part of the Free Software Foundation.

Apple and Lotus are trying to create a new form of legal monopoly: a copyright on a class of user interfaces. These monopolies would cause serious problems for users and developers of computer software and systems. Xerox, too, has tried to make a monopoly for itself on window systems; their suit against Apple was thrown out on a technicality, but Xerox has not said anything to indicate it wouldn’t try again.

Until a few years ago, the law seemed clear: no one could restrict others from using a user interface; programmers were free to implement any interface they chose. Imitating interfaces, sometimes with changes, was standard practice in the computer field. The interfaces we know evolved gradually in this way; for example, the Macintosh user interface drew ideas from the Xerox interface, which in turn drew on work done at Stanford and SRI. 1-2-3 imitated VisiCalc, and dBase imitated a database program from JPL.

Most computer companies, and nearly all computer users, were happy with this state of affairs. The companies that are suing say it does not offer “enough incentive” to develop their products, but they must have considered it “enough” when they made their decision to do so. It seems they are not satisfied with the opportunity to continue to compete in the marketplace—not even with a head start.

If companies like Xerox, Lotus, and Apple are permitted to make law through the courts, the precedent will hobble the software industry:

• Gratuitous incompatibilities will burden users. Imagine if each car manufacturer had to arrange the pedals in a different order.
• Software will become and remain more expensive. Users will be “locked in” to proprietary interfaces, for which there is no real competition.
• Large companies have an unfair advantage wherever lawsuits become commonplace. Since they can easily afford to sue, they can intimidate small companies with threats even when they don’t really have a case.
• User interface improvements will come slower, since incremental evolution through creative imitation will no longer be permitted.
• Even Apple, etc., will find it harder to make improvements if they can no longer adapt the good ideas that others introduce, for fear of weakening their own legal positions. Some users suggest that this stagnation may already have started.
• If you use GNU software, you might find it of some concern that user interface copyright will make it hard for the Free Software Foundation to develop programs compatible with the interfaces that you already know.

To protect our freedom from lawsuits like these, a group of programmers and users have formed a new grass-roots political organization, the League for Programming Freedom.

The purpose of the League is to oppose new monopolistic practices such as user-interface copyright and software patents; it calls for a return to the legal policies of the recent past, in which these practices were not allowed. The League is not concerned with free software as an issue, and not affiliated with the Free Software Foundation.

The League’s membership rolls include John McCarthy, inventor of Lisp, Marvin Minsky, founder of the Artificial Intelligence lab, Guy L. Steele, Jr., author of well-known books on Lisp and C, as well as Richard Stallman, the developer of GNU CC. Please join and add your name to the list. Membership dues in the League are $42 per year for programmers, managers and professionals; $10.50 for students; $21 for others.

The League needs both activist members and members who only pay their dues.

To join, or for more information, phone (617) 492-0023 or write to:

League for Programming Freedom
1 Kendall Square #143
P.O. Box 9171
Cambridge, MA 02139

You can also send electronic mail to league@prep.ai.mit.edu.

Here are some suggestions from the League for things you can do to protect your freedom to write programs:

• Don’t buy from Xerox, Lotus or Apple. Buy from their competitors or from the defendants they are suing.
• Don’t develop software to work with the systems made by these companies.
• Port your existing software to competing systems, so that you encourage users to switch.
• Write letters to company presidents to let them know their conduct is unacceptable.
• Tell your friends and colleagues about this issue and how it threatens to ruin the computer industry.
• Above all, don’t work for the look-and-feel plaintiffs, and don’t accept contracts from them.
• Write to Congress to explain the importance of this issue.

  House Subcommittee on Intellectual Property
  2137 Rayburn Bldg
  Washington, DC 20515
  
  Senate Subcommittee on Patents, Trademarks and Copyrights
  United States Senate
  Washington, DC 20510
  

  (These committees have received lots of mail already; let’s give them even more.)

Express your opinion! You can make a difference.

2 Known Causes of Trouble with GNU CC

This section describes known problems that affect users of GNU CC. Most of these are not GNU CC bugs per se—if they were, we would fix them. But the result for a user may be like the result of a bug.

Some of these problems are due to bugs in other software, some are missing features that are too much work to add, and some are places where people’s opinions differ as to what is best.

2.1 Actual Bugs We Haven’t Fixed Yet

• Loop unrolling doesn’t work properly for certain programs. This is because of difficulty in updating the debugging information within the loop being unrolled. We plan to revamp the representation of debugging information so that this will work properly, but we have not done this in version 2.2 because we don’t want to delay it any further.
• There is a bug in producing DBX output which outputs a structure tag even when a structure doesn’t have a tag. The reason we aren’t fixing this now is that a clean fix requires reorganizations that seem risky. We will do them after 2.2 is released.

2.2 Installation Problems

This is a list of problems (and some apparent problems which don’t really mean anything is wrong) that show up during installation of GNU CC.

• On certain systems, defining certain environment variables such as CC can interfere with the functioning of make.
• If you encounter seemingly strange errors when trying to build the compiler in a directory other than the source directory, it could be because you have previously configured the compiler in the source directory. Make sure you have done all the necessary preparations. @xref{Other Dir}.
• In previous versions of GNU CC, the gcc driver program looked for as and ld in various places such as files beginning with ‘/usr/local/lib/gcc-’. GNU CC version 2 looks for them in the directory ‘/usr/local/lib/gcc-lib/target/version’.

  Thus, to use a version of as or ld that is not the system default, for example gas or GNU ld, you must put them in that directory (or make links to them from that directory).

• Some commands executed when making the compiler may fail (return a non-zero status) and be ignored by make. These failures, which are often due to files that were not found, are expected, and can safely be ignored.
• It is normal to have warnings in compiling certain files about unreachable code and about enumeration type clashes. These files’ names begin with ‘insn-’.
• Sometimes make recompiles parts of the compiler when installing the compiler. In one case, this was traced down to a bug in make. Either ignore the problem or switch to GNU Make.
• Sometimes on a Sun 4 you may observe a crash in the program genflags or genoutput while building GCC. This is said to be due to a bug in sh. You can probably get around it by running genflags or genoutput manually and then retrying the make.
• On some versions of Ultrix, the system supplied compiler cannot compile ‘cp-parse.c’ because it cannot handle so many cases in a switch statement. You can avoid this problem by specifying ‘LANGUAGES=c’ when you compile GNU CC with the Ultrix compiler. Then you can compile the entire GNU compiler with GNU CC.
• If you use the 1.31 version of the MIPS assembler (such as was shipped with Ultrix 3.1), you will need to use the -fno-delayed-branch switch when optimizing floating point code. Otherwise, the assembler will complain when the GCC compiler fills a branch delay slot with a floating point instruction, such as add.d.
• Users have reported some problems with version 2.0 of the MIPS compiler tools that were shipped with Ultrix 4.1. Version 2.10 which came with Ultrix 4.2 seems to work fine.
• On HP 9000 series 300 or 400 running HP-UX release 8.0, there is a bug in the assembler that must be fixed before GNU CC can be built. This bug manifests itself during the first stage of compilation, while building ‘libgcc2.a’:

  _floatdisf
  cc1: warning: `-g' option not supported on this version of GCC
  cc1: warning: `-g1' option not supported on this version of GCC
  ./gcc: Internal compiler error: program as got fatal signal 11
  

  A patched version of the assembler is available by anonymous ftp from altdorf.ai.mit.edu as the file ‘archive/cph/hpux-8.0-assembler’. If you have HP software support, the patch can also be obtained directly from HP, as described in the following note:

  This is the patched assembler, to patch SR#1653-010439, where the assembler aborts on floating point constants.

  The bug is not really in the assembler, but in the shared library version of the function “cvtnum(3c)”. The bug on “cvtnum(3c)” is SR#4701-078451. Anyway, the attached assembler uses the archive library version of “cvtnum(3c)” and thus does not exhibit the bug.

  This patch is also known as PHCO_0800.

• Another assembler problem on the HP PA results in an error message like this while compiling part of ‘libgcc2.a’:

  as: /usr/tmp/cca08196.s @line#30 [err#1060]
    Argument 1 or 3 in FARG upper
           - lookahead = RTNVAL=GR
  

  This happens because HP changed the assembler syntax after system release 8.02. GNU CC assumes the newer syntax; if your assembler wants the older syntax, comment out this line in the file ‘pa1-hpux.h’:

  #define HP_FP_ARG_DESCRIPTOR_REVERSED
  

• Some versions of the Pyramid C compiler are reported to be unable to compile GNU CC. You must use an older version of GNU CC for bootstrapping. One indication of this problem is if you get a crash when GNU CC compiles the function muldi3 in file ‘libgcc2.c’.

  You may be able to succeed by getting GNU CC version 1, installing it, and using it to compile GNU CC version 2. The bug in the Pyramid C compiler does not seem to affect GNU CC version 1.

• On the Tower models 4n0 and 6n0, by default a process is not allowed to have more than one megabyte of memory. GNU CC cannot compile itself (or many other programs) with ‘-O’ in that much memory.

  To solve this problem, reconfigure the kernel adding the following line to the configuration file:

  MAXUMEM = 4096
  

• On the Altos 3068, programs compiled with GNU CC won’t work unless you fix a kernel bug. This happens using system versions V.2.2 1.0gT1 and V.2.2 1.0e and perhaps later versions as well. See the file ‘README.ALTOS’.

2.3 Cross-Compiler Problems

• Cross compilation can run into trouble for certain machines because some target machines’ assemblers require floating point numbers to be written as integer constants in certain contexts.

  The compiler writes these integer constants by examining the floating point value as an integer and printing that integer, because this is simple to write and independent of the details of the floating point representation. But this does not work if the compiler is running on a different machine with an incompatible floating point format, or even a different byte-ordering.

  In addition, correct constant folding of floating point values requires representing them in the target machine’s format. (The C standard does not quite require this, but in practice it is the only way to win.)

  It is now possible to overcome these problems by defining macros such as REAL_VALUE_TYPE. But doing so is a substantial amount of work for each target machine. @xref{Cross-compilation}.

• At present, the program ‘mips-tfile’ which adds debug support to object files on MIPS systems does not work in a cross compile environment.

2.4 Interoperation

This section lists various difficulties encountered in using GNU C or GNU C++ together with other compilers or with the assemblers, linkers and debuggers on certain systems.

• GNU C normally compiles functions to return small structures and unions in registers. Most other compilers arrange to return them just like larger structures and unions. This can lead to trouble when you link together code compiled by different compilers. To avoid the problem, you can use the option ‘-fpcc-struct-value’ when compiling with GNU CC.
• GNU C++ does not do name mangling in the same way as other C++ compilers. This means that object files compiled with one compiler cannot be used with another.

  GNU C++ also uses different techniques for arranging virtual function tables and the layout of class instances. In general, therefore, linking code compiled with different C++ compilers does not work.

• Older GDB versions sometimes fail to read the output of GNU CC version 2. If you have trouble, get GDB version 4.4 or later.
• DBX rejects some files produced by GNU CC, though it accepts similar constructs in output from PCC. Until someone can supply a coherent description of what is valid DBX input and what is not, there is nothing I can do about these problems. You are on your own.
• The GNU assembler (GAS) does not support PIC. To generate PIC code, you must use some other assembler, such as ‘/bin/as’.
• On some BSD systems including some versions of Ultrix, use of profiling causes static variable destructors (currently used only in C++) not to be run.
• On a Sun, linking using GNU CC fails to find a shared library and reports that the library doesn’t exist at all.

  This happens if you are using the GNU linker, because it does only static linking and looks only for unshared libraries. If you have a shared library with no unshared counterpart, the GNU linker won’t find anything.

  We hope to make a linker which supports Sun shared libraries, but please don’t ask when it will be finished—we don’t know.

• Sun forgot to include a static version of ‘libdl.a’ with some versions of SunOS (mainly 4.1). This results in undefined symbols when linking static binaries (that is, if you use ‘-static’). If you see undefined symbols _dlclose, _dlsym or _dlopen when linking, compile and link against the file ‘mit/util/misc/dlsym.c’ from the MIT version of X windows.
• On the HP PA machine, ADB sometimes fails to work on functions compiled with GNU CC. Specifically, it fails to work on functions that use alloca or variable-size arrays. This is because GNU CC doesn’t generate HPUX unwind descriptors for such functions. It may even be impossible to generate them.
• Profiling is not supported on the HP PA machine. Neither is debugging (‘-g’), unless you use the preliminary GNU tools (@pxref{Installation}).
• GNU CC on the HP PA handles variadic function arguments using a calling convention incompatible with the HP compiler. This is only a problem for routines that take va_list as parameters, such as vprintf. This may be fixed eventually.
• The current version of the assembler (‘/bin/as’) for the RS/6000 has certain problems that prevent the ‘-g’ option in GCC from working.

  IBM has produced a fixed version of the assembler. The replacement assembler is not a standard component of either AIX 3.1.5 or AIX 3.2, but is expected to become standard in a future distribution. This assembler is available from IBM as APAR IX22829. Yet more bugs have been fixed in a newer assembler, which will shortly be available as APAR IX26107. See the file ‘README.RS6000’ for more details on these assemblers.

• On the IBM RS/6000, compiling code of the form

  extern int foo;
  
  … foo …
  
  static int foo;
  

  will cause the linker to report an undefined symbol foo. Although this behavior differs from most other systems, it is not a bug because redefining an extern variable as static is undefined in ANSI C.

• On VMS, GAS versions 1.38.1 and earlier may cause spurious warning messages from the linker. These warning mess

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