[Bug libstdc++/52764] New: Including <cstdint> after <stdint.h> fails to define limit macros

[Bug libstdc++/52764] New: Including <cstdint> after <stdint.h> fails to define limit macros

[bmerry at gmail dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=52764

             Bug #: 52764
           Summary: Including <cstdint> after <stdint.h> fails to define
                    limit macros
    Classification: Unclassified
           Product: gcc
           Version: 4.6.1
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: libstdc++
        AssignedTo: unassigned@gcc.gnu.org
        ReportedBy: bmerry@gmail.com


Created attachment 27027
  --> http://gcc.gnu.org/bugzilla/attachment.cgi?id=27027
Preprocessed source from g++ -v -save-temps -std=c++0x gcc-stdint.cpp

Both <cstdint> and <tr1/cstdint> are implemented by defining
__STDC_LIMIT_MACROS, including <stdint.h> and then undefining the macro again.
However, if <stdint.h> has already been included (which may occur indirectly
via some third-party C library header) then the limit macros do not get
defined.

I'm not 100% sure this is a bug because the C and C++ standards seem to
contradict each other, but here's my reasoning:

Both TR1 and C++11 are explicit that <cstdint> will define the limit macros,
and C++11 also says "The macros defined by <cstdint> are provided
unconditionally. In particular, the symbols __STDC_LIMIT_MACROS and
__STDC_CONSTANT_MACROS (mentioned in footnotes 219, 220, and 222 in the C
standard) play no role in C++."

TR1 also says that "[<stdint.h>] behaves as if it includes the header
<cstdint>, and provides sufficient using declarations to declare in the global
namespace all type names defined in the header <cstdint>."

I've run into this on GCC 4.6.1, but from a quick look at
http://gcc.gnu.org/svn/gcc/trunk/libstdc++-v3/include/c_global/cstdint@185951
it looks like this hasn't changed.


Command line: 
g++ -c -std=c++0x gcc-stdint.cpp

Output:
gcc-stdint.cpp:4:26: error: ‘UINT32_MAX’ was not declared in this scope

Output of g++ -v:
Using built-in specs.
COLLECT_GCC=g++
COLLECT_LTO_WRAPPER=/usr/lib/gcc/x86_64-linux-gnu/4.6.1/lto-wrapper
Target: x86_64-linux-gnu
Configured with: ../src/configure -v --with-pkgversion='Ubuntu/Linaro
4.6.1-9ubuntu3' --with-bugurl=file:///usr/share/doc/gcc-4.6/README.Bugs
--enable-languages=c,c++,fortran,objc,obj-c++,go --prefix=/usr
--program-suffix=-4.6 --enable-shared --enable-linker-build-id
--with-system-zlib --libexecdir=/usr/lib --without-included-gettext
--enable-threads=posix --with-gxx-include-dir=/usr/include/c++/4.6
--libdir=/usr/lib --enable-nls --with-sysroot=/ --enable-clocale=gnu
--enable-libstdcxx-debug --enable-libstdcxx-time=yes --enable-plugin
--enable-objc-gc --disable-werror --with-arch-32=i686 --with-tune=generic
--enable-checking=release --build=x86_64-linux-gnu --host=x86_64-linux-gnu
--target=x86_64-linux-gnu
Thread model: posix
gcc version 4.6.1 (Ubuntu/Linaro 4.6.1-9ubuntu3)

[Bug libstdc++/52764] Including <cstdint> after <stdint.h> fails to define limit macros

[redi at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=52764

Jonathan Wakely <redi at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |NEW
   Last reconfirmed|                            |2012-03-29
     Ever Confirmed|0                           |1

--- Comment #1 from Jonathan Wakely <redi at gcc dot gnu.org> 2012-03-29 09:58:58 UTC ---
Including <stdint.h> alone should declare the macros, <cstdint> isn't needed to
demonstrate the bug.

The problem is that <stdint.h> has this:

/* The ISO C99 standard specifies that in C++ implementations these
   macros should only be defined if explicitly requested.  */
#if !defined __cplusplus || defined __STDC_LIMIT_MACROS

Which is indeed what C99 says, but C99 doesn't get to dictate rules to C++, and
C11 doesn't include that useless footnote.

GCC's own <stdint-gcc.h> should be fixed and glibc's <stdint.h> should be
fixed, and GCC's <stdint.h> should probably include

#ifdef __cplusplus
# define __STDC_LIMIT_MACROS
#endif

if GCC detects that glibc requires it in order to function correctly.

In short: not a libstdc++ bug!

[Bug libstdc++/52764] Including <cstdint> after <stdint.h> fails to define limit macros

[paolo.carlini at oracle dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=52764

Paolo Carlini <paolo.carlini at oracle dot com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |jsm28 at gcc dot gnu.org

--- Comment #2 from Paolo Carlini <paolo.carlini at oracle dot com> 2012-03-29 10:02:25 UTC ---
Let's add Joseph in CC: he spent a lot of time on GCC's own stdint.h (which by
now, afaik, is supported on most widespread targets) and I'm sure he can help
with it (and with glibc too, in case)

[Bug libstdc++/52764] Including <cstdint> after <stdint.h> fails to define limit macros

[redi at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=52764

--- Comment #3 from Jonathan Wakely <redi at gcc dot gnu.org> 2012-03-29 10:25:22 UTC ---
Joseph, I was just about to file a glibc bug, let me know if you want that
done.

Glibc's stdint.h (and GCC's stdint-gcc.h) must unconditionally define the
macros for C++11.

It's debatable whether they should be defined for C++03. The __STDC_xxx_MACROS
macros make sense there to avoid macro pollution, but arguably no strict C++03
program will include <stdint.h> anyway, so defining them unconditionally would
also be reasonable, and consistent with C++11.

GCC also needs to workaround the problem for "older" (i.e. all existing) glibc
versions.

[Bug libstdc++/52764] Including <cstdint> after <stdint.h> fails to define limit macros

[joseph at codesourcery dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=52764

--- Comment #4 from joseph at codesourcery dot com <joseph at codesourcery dot com> 2012-04-07 16:06:46 UTC ---
My previous suggestion stands of having the compiler predefine 
__STDC_LIMIT_MACROS and __STDC_CONSTANT_MACROS, whether for C++11 or 
generally for C++, to make all existing stdint.h headers work as desired.  
You could predefine in the compiler, or you could predefine in 
stdint-wrap.h when it includes a system stdint.h and remove the 
conditionals in stdint-gcc.h.  (In the header might be better because then 
you can use #ifndef to avoid any conflict with a user's definition of 
those macros.)

If the libstdc++ people conclude that these definitions should be present 
for all C++ versions, not just C++11, then the conditionals in glibc's 
stdint.h can be removed at leisure (the predefines in GCC will make the 
conditionals useless but harmless).

[Bug libstdc++/52764] Including <cstdint> after <stdint.h> fails to define limit macros

[paolo.carlini at oracle dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=52764

Paolo Carlini <paolo.carlini at oracle dot com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |jakub at gcc dot gnu.org

--- Comment #5 from Paolo Carlini <paolo.carlini at oracle dot com> 2012-09-27 12:04:00 UTC ---
Jakub, any chance you could help for this?

[Bug libstdc++/52764] Including <cstdint> after <stdint.h> fails to define limit macros

[paolo.carlini at oracle dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=52764

--- Comment #6 from Paolo Carlini <paolo.carlini at oracle dot com> 2012-09-27 12:38:48 UTC ---
I guess we should simply implement in stdint-wrap.h and stdint-gcc.h what
Joseph recommended. It seems safer to me to conditionalize the change on C++11.

[Bug c++/52764] Including <cstdint> after <stdint.h> fails to define limit macros

[paolo.carlini at oracle dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=52764

Paolo Carlini <paolo.carlini at oracle dot com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|NEW                         |ASSIGNED
          Component|libstdc++                   |c++

--- Comment #7 from Paolo Carlini <paolo.carlini at oracle dot com> 2012-09-27 15:10:09 UTC ---
On it.

[Bug c++/52764] Including <cstdint> after <stdint.h> fails to define limit macros

[paolo at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=52764

--- Comment #8 from paolo at gcc dot gnu.org <paolo at gcc dot gnu.org> 2012-10-06 23:06:09 UTC ---
Author: paolo
Date: Sat Oct  6 23:06:04 2012
New Revision: 192174

URL: http://gcc.gnu.org/viewcvs?root=gcc&view=rev&rev=192174
Log:
2012-10-06  Paolo Carlini  <paolo.carlini@oracle.com>

    PR c++/52764
    * ginclude/stdint-wrap.h: In C++11 if __STDC_HOSTED__ define
    __STDC_LIMIT_MACROS and __STDC_CONSTANT_MACROS.
    * ginclude/stdint-gcc.h: In C++11 unconditionally define
    limit and constant macros.

/testsuite
2012-10-06  Paolo Carlini  <paolo.carlini@oracle.com>

    PR c++/52764
    * g++.dg/cpp0x/stdint.C: New.

/libstdc++-v3
2012-10-06  Paolo Carlini  <paolo.carlini@oracle.com>

    PR c++/52764
    * include/c_global/cstdint: Remove __STDC_LIMIT_MACROS and
    __STDC_CONSTANT_MACROS related macros.

Added:
    trunk/gcc/testsuite/g++.dg/cpp0x/stdint.C
Modified:
    trunk/gcc/ChangeLog
    trunk/gcc/ginclude/stdint-gcc.h
    trunk/gcc/ginclude/stdint-wrap.h
    trunk/gcc/testsuite/ChangeLog
    trunk/libstdc++-v3/ChangeLog
    trunk/libstdc++-v3/include/c_global/cstdint

[Bug c++/52764] Including <cstdint> after <stdint.h> fails to define limit macros

[paolo.carlini at oracle dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=52764

Paolo Carlini <paolo.carlini at oracle dot com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|ASSIGNED                    |RESOLVED
         Resolution|                            |FIXED
   Target Milestone|---                         |4.8.0

--- Comment #9 from Paolo Carlini <paolo.carlini at oracle dot com> 2012-10-06 23:10:58 UTC ---
Fixed.