gcc.texi

GUN开源阻止下的编译器GCC

programs:

@itemize @bullet
@item
Tell your friends and colleagues about this issue and how it threatens
to ruin the computer industry.

@item
Mention that you are a League member in your @file{.signature}, and
mention the League's email address for inquiries.

@item
Ask the companies you consider working for or working with to make
statements against software monopolies, and give preference to those
that do.

@item
When employers ask you to sign contracts giving them copyright on your
work, insist on a clause saying they will not claim the copyright covers
imitating the interface.

@item
When employers ask you to sign contracts giving them patent rights,
insist on clauses saying they can use these rights only defensively.
Don't rely on ``company policy,'' since that can change at any time;
don't rely on an individual executive's private word, since that person
may be replaced.  Get a commitment just as binding as the commitment
they get from you.

@item
Write to Congress to explain the importance of these issues.

@display
House Subcommittee on Intellectual Property
2137 Rayburn Bldg
Washington, DC 20515

Senate Subcommittee on Patents, Trademarks and Copyrights
United States Senate
Washington, DC 20510
@end display

(These committees have received lots of mail already; let's give them
even more.)
@end itemize

Democracy means nothing if you don't use it.  Stand up and be counted!
@ifset USING
@node G++ and GCC
@chapter Compile C, C++, or Objective C

@cindex Objective C
The C, C++, and Objective C versions of the compiler are integrated; the
GNU C compiler can compile programs written in C, C++, or Objective C.

@cindex GCC
``GCC'' is a common shorthand term for the GNU C compiler.  This is both
the most general name for the compiler, and the name used when the
emphasis is on compiling C programs.

@cindex C++
@cindex G++
When referring to C++ compilation, it is usual to call the compiler
``G++''.  Since there is only one compiler, it is also accurate to call
it ``GCC'' no matter what the language context; however, the term
``G++'' is more useful when the emphasis is on compiling C++ programs.

We use the name ``GNU CC'' to refer to the compilation system as a
whole, and more specifically to the language-independent part of the
compiler.  For example, we refer to the optimization options as
affecting the behavior of ``GNU CC'' or sometimes just ``the compiler''.

Front ends for other languages, such as Ada 9X, Fortran, Modula-3, and
Pascal, are under development.  These front-ends, like that for C++, are
built in subdirectories of GNU CC and link to it.  The result is an
integrated compiler that can compile programs written in C, C++,
Objective C, or any of the languages for which you have installed front
ends.

In this manual, we only discuss the options for the C, Objective-C, and
C++ compilers and those of the GNU CC core.  Consult the documentation
of the other front ends for the options to use when compiling programs
written in other languages.

@cindex compiler compared to C++ preprocessor
@cindex intermediate C version, nonexistent
@cindex C intermediate output, nonexistent
G++ is a @emph{compiler}, not merely a preprocessor.  G++ builds object
code directly from your C++ program source.  There is no intermediate C
version of the program.  (By contrast, for example, some other
implementations use a program that generates a C program from your C++
source.)  Avoiding an intermediate C representation of the program means
that you get better object code, and better debugging information.  The
GNU debugger, GDB, works with this information in the object code to
give you comprehensive C++ source-level editing capabilities
(@pxref{C,,C and C++,gdb.info, Debugging with GDB}).

@c FIXME!  Someone who knows something about Objective C ought to put in
@c a paragraph or two about it here, and move the index entry down when
@c there is more to point to than the general mention in the 1st par.

@include invoke.texi

@include install.texi

@include extend.texi

@node Trouble
@chapter Known Causes of Trouble with GNU CC
@cindex bugs, known
@cindex installation trouble
@cindex known causes of trouble

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.

@menu
* Actual Bugs::		      Bugs we will fix later.
* Installation Problems::     Problems that manifest when you install GNU CC.
* Cross-Compiler Problems::   Common problems of cross compiling with GNU CC.
* Interoperation::      Problems using GNU CC with other compilers,
			   and with certain linkers, assemblers and debuggers.
* External Bugs::	Problems compiling certain programs.
* Incompatibilities::   GNU CC is incompatible with traditional C.
* Fixed Headers::       GNU C uses corrected versions of system header files.
                           This is necessary, but doesn't always work smoothly.
* Standard Libraries::  GNU C uses the system C library, which might not be 
                           compliant with the ISO/ANSI C standard.
* Disappointments::     Regrettable things we can't change, but not quite bugs.
* C++ Misunderstandings::     Common misunderstandings with GNU C++.
* Protoize Caveats::    Things to watch out for when using @code{protoize}.
* Non-bugs::		Things we think are right, but some others disagree.
* Warnings and Errors:: Which problems in your code get warnings,
                         and which get errors.
@end menu

@node Actual Bugs
@section Actual Bugs We Haven't Fixed Yet

@itemize @bullet
@item
The @code{fixincludes} script interacts badly with automounters; if the
directory of system header files is automounted, it tends to be
unmounted while @code{fixincludes} is running.  This would seem to be a
bug in the automounter.  We don't know any good way to work around it.

@item
The @code{fixproto} script will sometimes add prototypes for the
@code{sigsetjmp} and @code{siglongjmp} functions that reference the
@code{jmp_buf} type before that type is defined.  To work around this,
edit the offending file and place the typedef in front of the
prototypes.

@item
There are several obscure case of mis-using struct, union, and 
enum tags that are not detected as errors by the compiler.

@item
When @samp{-pedantic-errors} is specified, GNU C will incorrectly give
an error message when a function name is specified in an expression
involving the comma operator.

@item
Loop unrolling doesn't work properly for certain C++ programs.  This is
a bug in the C++ front end.  It sometimes emits incorrect debug info, and
the loop unrolling code is unable to recover from this error.
@end itemize

@node Installation Problems
@section 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.

@itemize @bullet
@item
On certain systems, defining certain environment variables such as
@code{CC} can interfere with the functioning of @code{make}.

@item
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}.

@item
If you build GNU CC on a BSD system using a directory stored in a System
V file system, problems may occur in running @code{fixincludes} if the
System V file system doesn't support symbolic links.  These problems
result in a failure to fix the declaration of @code{size_t} in
@file{sys/types.h}.  If you find that @code{size_t} is a signed type and
that type mismatches occur, this could be the cause.

The solution is not to use such a directory for building GNU CC.

@item
In previous versions of GNU CC, the @code{gcc} driver program looked for
@code{as} and @code{ld} in various places; for example, in files
beginning with @file{/usr/local/lib/gcc-}.  GNU CC version 2 looks for
them in the directory
@file{/usr/local/lib/gcc-lib/@var{target}/@var{version}}.

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

@item
Some commands executed when making the compiler may fail (return a
non-zero status) and be ignored by @code{make}.  These failures, which
are often due to files that were not found, are expected, and can safely
be ignored.

@item
It is normal to have warnings in compiling certain files about
unreachable code and about enumeration type clashes.  These files' names
begin with @samp{insn-}.  Also, @file{real.c} may get some warnings that
you can ignore.

@item
Sometimes @code{make} recompiles parts of the compiler when installing
the compiler.  In one case, this was traced down to a bug in
@code{make}.  Either ignore the problem or switch to GNU Make.

@item
If you have installed a program known as purify, you may find that it
causes errors while linking @code{enquire}, which is part of building
GNU CC.  The fix is to get rid of the file @code{real-ld} which purify
installs---so that GNU CC won't try to use it.

@item 
On SLS 1.01, a Linux-based GNU system, there is a problem with
@file{libc.a}: it does not contain the obstack functions.  However, GNU
CC assumes that the obstack functions are in @file{libc.a} when it is
the GNU C library.  To work around this problem, change the
@code{__GNU_LIBRARY__} conditional around line 31 to @samp{#if 1}.

@item
On some 386 systems, building the compiler never finishes because
@code{enquire} hangs due to a hardware problem in the motherboard---it
reports floating point exceptions to the kernel incorrectly.  You can
install GNU CC except for @file{float.h} by patching out the command to
run @code{enquire}.  You may also be able to fix the problem for real by
getting a replacement motherboard.  This problem was observed in
Revision E of the Micronics motherboard, and is fixed in Revision F.
It has also been observed in the MYLEX MXA-33 motherboard.

If you encounter this problem, you may also want to consider removing
the FPU from the socket during the compilation.  Alternatively, if you
are running SCO Unix, you can reboot and force the FPU to be ignored.
To do this, type @samp{hd(40)unix auto ignorefpu}.

@item
On some 386 systems, GNU CC crashes trying to compile @file{enquire.c}.
This happens on machines that don't have a 387 FPU chip.  On 386
machines, the system kernel is supposed to emulate the 387 when you
don't have one.  The crash is due to a bug in the emulator.

One of these systems is the Unix from Interactive Systems: 386/ix.
On this system, an alternate emulator is provided, and it does work.
To use it, execute this command as super-user:

@example
ln /etc/emulator.rel1 /etc/emulator
@end example

@noindent
and then reboot the system.  (The default emulator file remains present
under the name @file{emulator.dflt}.)

Try using @file{/etc/emulator.att}, if you have such a problem on the
SCO system.

Another system which has this problem is Esix.  We don't know whether it
has an alternate emulator that works.

On NetBSD 0.8, a similar problem manifests itself as these error messages:

@example
enquire.c: In function `fprop':
enquire.c:2328: floating overflow
@end example

@item
On SCO systems, when compiling GNU CC with the system's compiler,
do not use @samp{-O}.  Some versions of the system's compiler miscompile
GNU CC with @samp{-O}.

@cindex @code{genflags}, crash on Sun 4
@item
Sometimes on a Sun 4 you may observe a crash in the program
@code{genflags} or @code{genoutput} while building GNU CC.  This is said to
be due to a bug in @code{sh}.  You can probably get around it by running
@code{genflags} or @code{genoutput} manually and then retrying the
@code{make}.

@item
On Solaris 2, executables of GNU CC version 2.0.2 are commonly
available, but they have a bug that shows up when compiling current
versions of GNU CC: undefined symbol errors occur during assembly if you
use @samp{-g}.

The solution is to compile the current version of GNU CC without
@samp{-g}.  That makes a working compiler which you can use to recompile
with @samp{-g}.

@item
Solaris 2 comes with a number of optional OS packages.  Some of these
packages are needed to use GNU CC fully.  If you did not install all
optional packages when installing Solaris, you will need to verify that
the packages that GNU CC needs are installed.

To check whether an optional package is installed, use
the @code{pkginfo} command.  To add an optional package, use the
@code{pkgadd} command.  For further details, see the Solaris
documentation.

For Solaris 2.0 and 2.1, GNU CC needs six packages: @samp{SUNWarc},
@samp{SUNWbtool}, @samp{SUNWesu}, @samp{SUNWhea}, @samp{SUNWlibm}, and
@samp{SUNWtoo}.  

For Solaris 2.2, GNU CC needs an additional seventh package: @samp{SUNWsprot}.

@item
On Solaris 2, trying to use the linker and other tools in
@file{/usr/ucb} to install GNU CC has been observed to cause trouble.
For example, the linker may hang indefinitely.  The fix is to remove
@file{/usr/ucb} from your @code{PATH}.

@item