Hello,
2009/10/22 Sisyphus <[email protected]>:
> Hi,
> The test script (try.c):
>
> ###############################
> C:\_32\C>type try.c
> #include <stdio.h>
>
> int main(void) {
>
> #ifdef NO_OLDNAMES
> printf("\"NO_OLDNAMES\" defined\n");
> #else
> printf("\"NO_OLDNAMES\" not defined\n");
> #endif
>
> #define popen 1
>
> printf("%d\n", popen);
>
> return 0;
>
> }
>
>
> C:\_32\C>
> ###############################
>
> Irrespective of whether I compile that script with mingw32 (either 3.4.5 or
> 4.4.0) or mingw64 (4.5.0), the executable outputs the same:
>
> ###############################
> C:\_32\C>try
> "NO_OLDNAMES" not defined
> 1
>
> C:\_32\C>
> ###############################
>
> No problem with that ... what puzzles me is that, while the script compiles
> silently with mingw32 (even with '-pedantic -Wall') when I compile with
> mingw64 I get a warning about popen being redefined:
>
> ###############################
> C:\_32\C>x86_64-w64-mingw32-gcc -o try.exe try.c
> try.c: In function 'main':
> try.c:12:0: warning: "popen" redefined
> c:/_64/mingw64/lib/gcc/../../x86_64-w64-mingw32/include/stdio.h:213:0: note:
> this is the location of the previous definition
Well, I am not sure why we used here define instead of prototyping.
IIRC it had something to do with previous defined popen, but I think I
can solve this better here.
> C:\_32\C>
> ###############################
>
> Why the difference ? (It's not so much a question of "Why do I get that
> warning with mingw64 ?" ... rather, what puzzles me is "Why *don't* I get
> that warning with mingw32 ?".)
Well you would get a error by mingw.org, if you would define popen
before including headers.
> The relevant section of mingw64's stdio.h is:
>
> 212: #if !defined(NO_OLDNAMES) && !defined(popen)
> 213: #define popen _popen
> 214: #define pclose _pclose
> 215: #endif
>
> With mingw32's stdio.h, we have:
>
> #ifndef NO_OLDNAMES
> _CRTIMP FILE* __cdecl __MINGW_NOTHROW popen (const char*, const char*);
> _CRTIMP int __cdecl __MINGW_NOTHROW pclose (FILE*);
> #endif
>
> Is the redefinition not taking place with mingw32 ? ... or is it just that
> no warning is being produced ?
> (I'm currently looking at "__MINGW_NOTHROW" and wondering what it does.)
>
> Does anyone have info on what "NO_OLDNAMES" is about, and/or the
> ramifications of explicitly defining it ?
NO_OLDNAMES is an option to hide old API, which is deprecated by MS.
These are mainly POSIX function names.
> When building perl with mingw64, I'm getting lots of warnings about popen
> and pclose being redefined - and I'd like a good way of getting rid of
> them. (I also get the same warnings when building perl modules, as popen and
> pclose are defined in perl's XSUB.h.)
>
> See below for the respective 'gcc -v' outputs.
>
> Cheers,
> Rob
>
Cheers,
Kai
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