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This file contains invisible Unicode characters
This file contains invisible Unicode characters that are indistinguishable to humans but may be processed differently by a computer. If you think that this is intentional, you can safely ignore this warning. Use the Escape button to reveal them.
This is Info file gcc.info, produced by Makeinfo-1.47 from the input
file gcc.texi.
This file documents the use and the internals of the GNU compiler.
Copyright (C) 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.

File: gcc.info, Node: Top, Next: Copying, Up: (DIR)
Introduction
************
This manual documents how to run, install and port the GNU C
compiler, as well as its new features and incompatibilities, and how to
report bugs. It corresponds to GNU CC version 2.2.
* Menu:
* Copying:: GNU General Public License says
how you can copy and share GNU CC.
* Contributors:: People who have contributed to GNU CC.
* Boycott:: Protect your freedom--fight "look and feel".
* Invoking GCC:: Command options supported by `gcc'.
* Installation:: How to configure, compile and install GNU CC.
* Extensions:: GNU extensions to the C language.
* Trouble:: If you have trouble installing GNU CC.
* Bugs:: How, why and where to report bugs.
* Service:: How to find suppliers of support for GNU CC.
* VMS:: Using GNU CC on VMS.
* Portability:: Goals of GNU CC's portability features.
* Interface:: Function-call interface of GNU CC output.
* Passes:: Order of passes, what they do, and what each file is for.
* RTL:: The intermediate representation that most passes work on.
* Machine Desc:: How to write machine description instruction patterns.
* Target Macros:: How to write the machine description C macros.
* Config:: Writing the `xm-MACHINE.h' file.
* Index:: Index of concepts and symbol names.

File: gcc.info, Node: Copying, Next: Contributors, Prev: Top, Up: Top
GNU GENERAL PUBLIC LICENSE
**************************
Version 2, June 1991
Copyright (C) 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.
TERMS AND CONDITIONS FOR COPYING, DISTRIBUTION AND MODIFICATION
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:
a. You must cause the modified files to carry prominent notices
stating that you changed the files and the date of any change.
b. 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.
c. 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:
a. 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,
b. 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,
c. 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.
NO WARRANTY
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.
END OF TERMS AND CONDITIONS
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.

File: gcc.info, Node: Contributors, Next: Boycott, Prev: Copying, Up: Top
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.

File: gcc.info, Node: Boycott, Next: Invoking GCC, Prev: Contributors, Up: Top
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.

File: gcc.info, Node: Invoking GCC, Next: Installation, Prev: Boycott, Up: Top
GNU CC Command Options
**********************
When you invoke GNU CC, it normally does preprocessing, compilation,
assembly and linking. The "overall options" allow you to stop this
process at an intermediate stage. For example, the `-c' option says
not to run the linker. Then the output consists of object files output
by the assembler.
Other options are passed on to one stage of processing. Some options
control the preprocessor and others the compiler itself. Yet other
options control the assembler and linker; most of these are not
documented here, since you rarely need to use any of them.
The GNU C compiler uses a command syntax much like the Unix C
compiler. The `gcc' program accepts options and file names as operands.
Multiple single-letter options may *not* be grouped: `-dr' is very
different from `-d -r'.
You can mix options and other arguments. For the most part, the
order you use doesn't matter; `gcc' reorders the command-line options so
that the choices specified by option flags are applied to all input
files. Order does matter when you use several options of the same kind;
for example, if you specify `-L' more than once, the directories are
searched in the order specified.
Many options have long names starting with `-f' or with `-W'--for
example, `-fforce-mem', `-fstrength-reduce', `-Wformat' and so on.
Most of these have both positive and negative forms; the negative form
of `-ffoo' would be `-fno-foo'. This manual documents only one of
these two forms, whichever one is not the default.
Here is a summary of all the options, grouped by type. Explanations
are in the following sections.
*Overall Options*
*Note Options Controlling the Kind of Output: Overall Options.
-c -S -E -o FILE -pipe -v -x LANGUAGE
*Language Options*
*Note Options Controlling Dialect: Dialect Options.
-ansi -fbuiltin -fcond-mismatch -fno-asm
-fsigned-bitfields -fsigned-char
-funsigned-bitfields -funsigned-char -fwritable-strings
-traditional -traditional-cpp -trigraphs
*Warning Options*
*Note Options to Request or Suppress Warnings: Warning Options.
-fsyntax-only -pedantic -pedantic-errors
-w -W -Wall -Waggregate-return
-Wcast-align -Wcast-qual -Wcomment -Wconversion -Werror
-Wformat -Wid-clash-LEN -Wimplicit -Wimport
-Winline -Wmissing-prototypes
-Wparentheses -Wpointer-arith -Wreturn-type -Wshadow
-Wstrict-prototypes -Wswitch -Wtraditional -Wtrigraphs
-Wuninitialized -Wunused -Wwrite-strings -Wchar-subscripts
*Debugging Options*
*Note Options for Debugging Your Program or GCC: Debugging Options.
-a -dLETTERS -fpretend-float
-g -gLEVEL -ggdb -gdwarf
-gstabs -gstabs+ -gcoff -gxcoff
-p -pg -save-temps
*Optimization Options*
*Note Options that Control Optimization: Optimize Options.
-fcaller-saves -fcse-follow-jumps -fcse-skip-blocks
-fdelayed-branch -fexpensive-optimizations -ffast-math
-ffloat-store -fforce-addr -fforce-mem -finline
-finline-functions -fkeep-inline-functions
-fno-defer-pop -fno-function-cse -fomit-frame-pointer
-frerun-cse-after-loop -fschedule-insns -fschedule-insns2
-fstrength-reduce -fthread-jumps
-funroll-all-loops -funroll-loops
-O -O2
*Preprocessor Options*
*Note Options Controlling the Preprocessor: Preprocessor Options.
-C -dD -dM -dN
-DMACRO[=DEFN] -E -H
-include FILE -imacros FILE
-M -MD -MM -MMD -nostdinc -P -trigraphs -UMACRO
*Linker Options*
*Note Options for Linking: Link Options.
OBJECT-FILE-NAME
-lLIBRARY -nostdlib -static
*Directory Options*
*Note Options for Directory Search: Directory Options.
-BPREFIX -IDIR -I- -LDIR
*Target Options*
*Note Target Machine and Compiler Version: Target Options.
-b MACHINE -V VERSION
*Machine Dependent Options*
*Note Hardware Models and Configurations: Submodel Options.
*M680x0 Options*
-m68000 -m68020 -m68881 -mbitfield -mc68000 -mc68020 -mfpa
-mnobitfield -mrtd -mshort -msoft-float
*VAX Options*
-mg -mgnu -munix
*SPARC Options*
-mforce-align -mfpu -mno-epilogue
*Convex Options*
-margcount -mc1 -mc2 -mnoargcount
*AMD29K Options*
-m29000 -m29050 -mbw -mdw -mkernel-registers -mlarge
-mnbw -mnodw -msmall -mstack-check -muser-registers
*M88K Options*
-m88000 -m88100 -m88110 -mbig-pic -mcheck-zero-division
-mhandle-large-shift -midentify-revision
-mno-check-zero-division -mno-ocs-debug-info
-mno-ocs-frame-position -mno-optimize-arg-area -mno-underscores
-mocs-debug-info -mocs-frame-position -moptimize-arg-area
-mshort-data-NUM -msvr3 -msvr4 -mtrap-large-shift
-muse-div-instruction -mversion-03.00 -mwarn-passed-structs
*RS/6000 Options*
-mfp-in-toc -mno-fop-in-toc
*RT Options*
-mcall-lib-mul -mfp-arg-in-fpregs -mfp-arg-in-gregs
-mfull-fp-blocks -mhc-struct-return -min-line-mul
-mminimum-fp-blocks -mnohc-struct-return
*MIPS Options*
-mcpu=CPU TYPE -mips2 -mips3 -mint64 -mlong64 -mlonglong128
-mmips-as -mgas -mrnames -mno-rnames -mgpopt -mno-gpopt -mstats
-mno-stats -mmemcpy -mno-memcpy -mno-mips-tfile -mmips-tfile
-msoft-float -mhard-float -mabicalls -mno-abicalls -mhalf-pic
-mno-half-pic -G NUM -nocpp
*i386 Options*
-m486 -msoft-float
*Code Generation Options*
*Note Options for Code Generation Conventions: Code Gen Options.
-fcall-saved-REG -fcall-used-REG -ffixed-REG
-fno-common -fpcc-struct-return -fpic -fPIC -fshared-data
-fshort-enums -fshort-double -fvolatile
* Menu:
* Overall Options:: Controlling the kind of output:
an executable, object files, assembler files,
or preprocessed source.
* Dialect Options:: Controlling the variant of C language compiled.
* Warning Options:: How picky should the compiler be?
* Debugging Options:: Symbol tables, measurements, and debugging dumps.
* Optimize Options:: How much optimization?
* Preprocessor Options:: Controlling header files and macro definitions.
Also, getting dependency information for Make.
* Link Options:: Specifying libraries and so on.
* Directory Options:: Where to find header files and libraries.
Where to find the compiler executable files.
* Target Options:: Running a cross-compiler, or an old version of GNU CC.
* Submodel Options:: Specifying minor hardware or convention variations,
such as 68010 vs 68020.
* Code Gen Options:: Specifying conventions for function calls, data layout
and register usage.
* Environment Variables:: Env vars that affect GNU CC.

File: gcc.info, Node: Overall Options, Next: Dialect Options, Prev: Invoking GCC, Up: Invoking GCC
Options Controlling the Kind of Output
======================================
Compilation can involve up to four stages: preprocessing, compilation
proper, assembly and linking, always in that order. The first three
stages apply to an individual source file, and end by producing an
object file; linking combines all the object files (those newly
compiled, and those specified as input) into an executable file.
For any given input file, the file name suffix determines what kind
of compilation is done:
`FILE.c'
C source code which must be preprocessed.
`FILE.i'
C source code which should not be preprocessed.
`FILE.m'
Objective-C source code
`FILE.h'
C header file (not to be compiled or linked).
`FILE.cc'
`FILE.cxx'
`FILE.C'
C++ source code which must be preprocessed.
`FILE.s'
Assembler code.
`FILE.S'
Assembler code which must be preprocessed.
`OTHER'
An object file to be fed straight into linking. Any file name with
no recognized suffix is treated this way.
You can specify the input language explicitly with the `-x' option:
`-x LANGUAGE'
Specify explicitly the LANGUAGE for the following input files
(rather than choosing a default based on the file name suffix).
This option applies to all following input files until the next
`-x' option. Possible values of LANGUAGE are `c', `objective-c',
`c-header', `c++', `cpp-output', `assembler', and
`assembler-with-cpp'.
`-x none'
Turn off any specification of a language, so that subsequent files
are handled according to their file name suffixes (as they are if
`-x' has not been used at all).
If you only want some of the stages of compilation, you can use `-x'
(or filename suffixes) to tell `gcc' where to start, and one of the
options `-c', `-S', or `-E' to say where `gcc' is to stop. Note that
some combinations (for example, `-x cpp-output -E' instruct `gcc' to do
nothing at all.
`-c'
Compile or assemble the source files, but do not link. The linking
stage simply is not done. The ultimate output is in the form of an
object file for each source file.
By default, the object file name for a source file is made by
replacing the suffix `.c', `.i', `.s', etc., with `.o'.
Unrecognized input files, not requiring compilation or assembly,
are ignored.
`-S'
Stop after the stage of compilation proper; do not assemble. The
output is in the form of an assembler code file for each
non-assembler input file specified.
By default, the assembler file name for a source file is made by
replacing the suffix `.c', `.i', etc., with `.s'.
Input files that don't require compilation are ignored.
`-E'
Stop after the preprocessing stage; do not run the compiler
proper. The output is in the form of preprocessed source code,
which is sent to the standard output.
Input files which don't require preprocessing are ignored.
`-o FILE'
Place output in file FILE. This applies regardless to whatever
sort of output is being produced, whether it be an executable file,
an object file, an assembler file or preprocessed C code.
Since only one output file can be specified, it does not make
sense to use `-o' when compiling more than one input file, unless
you are producing an executable file as output.
If `-o' is not specified, the default is to put an executable file
in `a.out', the object file for `SOURCE.SUFFIX' in `SOURCE.o', its
assembler file in `SOURCE.s', and all preprocessed C source on
standard output.
`-v'
Print (on standard error output) the commands executed to run the
stages of compilation. Also print the version number of the
compiler driver program and of the preprocessor and the compiler
proper.
`-pipe'
Use pipes rather than temporary files for communication between the
various stages of compilation. This fails to work on some systems
where the assembler is unable to read from a pipe; but the GNU
assembler has no trouble.

File: gcc.info, Node: Dialect Options, Next: Warning Options, Prev: Overall Options, Up: Invoking GCC
Options Controlling Dialect
===========================
The following options control the dialect of C that the compiler
accepts:
`-ansi'
Support all ANSI standard C programs.
This turns off certain features of GNU C that are incompatible
with ANSI C, such as the `asm', `inline' and `typeof' keywords, and
predefined macros such as `unix' and `vax' that identify the type
of system you are using. It also enables the undesirable and
rarely used ANSI trigraph feature, and disallows `$' as part of
identifiers.
The alternate keywords `__asm__', `__extension__', `__inline__'
and `__typeof__' continue to work despite `-ansi'. You would not
want to use them in an ANSI C program, of course, but it useful to
put them in header files that might be included in compilations
done with `-ansi'. Alternate predefined macros such as `__unix__'
and `__vax__' are also available, with or without `-ansi'.
The `-ansi' option does not cause non-ANSI programs to be rejected
gratuitously. For that, `-pedantic' is required in addition to
`-ansi'. *Note Warning Options::.
The macro `__STRICT_ANSI__' is predefined when the `-ansi' option
is used. Some header files may notice this macro and refrain from
declaring certain functions or defining certain macros that the
ANSI standard doesn't call for; this is to avoid interfering with
any programs that might use these names for other things.
The functions `alloca', `abort', `exit', and `_exit' are not
builtin functions when `-ansi' is used.
`-fno-asm'
Do not recognize `asm', `inline' or `typeof' as a keyword. These
words may then be used as identifiers. You can use `__asm__',
`__inline__' and `__typeof__' instead. `-ansi' implies `-fno-asm'.
`-fno-builtin'
Don't recognize built-in functions that do not begin with two
leading underscores. Currently, the functions affected include
`alloca', `abort', `exit', `_exit', `abs', `fabs', `labs',
`memcpy', `memcmp', `strcmp', `strcpy', `strlen', and `sqrt'.
The `-ansi' option prevents `alloca' and `_exit' from being
builtin functions.
`-trigraphs'
Support ANSI C trigraphs. You don't want to know about this
brain-damage. The `-ansi' option implies `-trigraphs'.
`-traditional'
Attempt to support some aspects of traditional C compilers.
Specifically:
* All `extern' declarations take effect globally even if they
are written inside of a function definition. This includes
implicit declarations of functions.
* The keywords `typeof', `inline', `signed', `const' and
`volatile' are not recognized. (You can still use the
alternative keywords such as `__typeof__', `__inline__', and
so on.)
* Comparisons between pointers and integers are always allowed.
* Integer types `unsigned short' and `unsigned char' promote to
`unsigned int'.
* Out-of-range floating point literals are not an error.
* String "constants" are not necessarily constant; they are
stored in writable space, and identical looking constants are
allocated separately. (This is the same as the effect of
`-fwritable-strings'.)
* All automatic variables not declared `register' are preserved
by `longjmp'. Ordinarily, GNU C follows ANSI C: automatic
variables not declared `volatile' may be clobbered.
* In the preprocessor, comments convert to nothing at all,
rather than to a space. This allows traditional token
concatenation.
* In the preprocessor, macro arguments are recognized within
string constants in a macro definition (and their values are
stringified, though without additional quote marks, when they
appear in such a context). The preprocessor always considers
a string constant to end at a newline.
* The predefined macro `__STDC__' is not defined when you use
`-traditional', but `__GNUC__' is (since the GNU extensions
which `__GNUC__' indicates are not affected by
`-traditional'). If you need to write header files that work
differently depending on whether `-traditional' is in use, by
testing both of these predefined macros you can distinguish
four situations: GNU C, traditional GNU C, other ANSI C
compilers, and other old C compilers.
You may wish to use `-fno-builtin' as well as `-traditional' if
your program uses names that are normally GNU C builtin functions
for other purposes of its own.
`-traditional-cpp'
Attempt to support some aspects of traditional C preprocessors.
This includes the last three items in the table immediately above,
but none of the other effects of `-traditional'.
`-fcond-mismatch'
Allow conditional expressions with mismatched types in the second
and third arguments. The value of such an expression is void.
`-funsigned-char'
Let the type `char' be unsigned, like `unsigned char'.
Each kind of machine has a default for what `char' should be. It
is either like `unsigned char' by default or like `signed char' by
default.
Ideally, a portable program should always use `signed char' or
`unsigned char' when it depends on the signedness of an object.
But many programs have been written to use plain `char' and expect
it to be signed, or expect it to be unsigned, depending on the
machines they were written for. This option, and its inverse, let
you make such a program work with the opposite default.
The type `char' is always a distinct type from each of `signed
char' or `unsigned char', even though its behavior is always just
like one of those two.
`-fsigned-char'
Let the type `char' be signed, like `signed char'.
Note that this is equivalent to `-fno-unsigned-char', which is the
negative form of `-funsigned-char'. Likewise, `-fno-signed-char'
is equivalent to `-funsigned-char'.
`-fsigned-bitfields'
`-funsigned-bitfields'
`-fno-signed-bitfields'
`-fno-unsigned-bitfields'
These options control whether a bitfield is signed or unsigned,
when the declaration does not use either `signed' or `unsigned'.
By default, such a bitfield is signed, because this is consistent:
the basic integer types such as `int' are signed types.
However, when `-traditional' is used, bitfields are all unsigned
no matter what.
`-fwritable-strings'
Store string constants in the writable data segment and don't
uniquize them. This is for compatibility with old programs which
assume they can write into string constants. `-traditional' also
has this effect.
Writing into string constants is a very bad idea; "constants"
should be constant.

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