Yitzchak Scott-Thoennes wrote:
>On Mon, Jun 27, 2005 at 10:46:19AM +0100, Steve Hay wrote:
>
>
>>win32/win32.c currently generates warnings under gcc. The problem is
>>reproduced by:
>>
>>#include <process.h>
>>int main() {
>> const char *cmdname;
>> const char *const *argv;
>> return execv(cmdname, (char *const *)argv);
>>}
>>
>>which causes gcc to complain:
>>
>>test.c:5: warning: passing arg 2 of `execv' from incompatible pointer type
>>
>>In MinGW (and VC++) execv's 2nd arg is const char *const *, so simply
>>removing the cast makes it happy. However, in Borland C execv's 2nd arg
>>is just char * const * (hence the reason for the cast in the first place
>>-- must have been written by a Borland C user!), so removing the cast
>>makes bcc32 complain:
>>
>>Warning W8075 test.c 5: Suspicious pointer conversion in function main
>>
>>How can I keep both compilers (gcc and bcc32) happy? Is #ifdef hell the
>>only way, e.g.
>>
>>#ifdef __BORLANDC__
>> return execv(cmdname, (char *const *)argv);
>>#else
>> return execv(cmdname, argv);
>>#endif
>>
>>Why does gcc complain in the first place, though? I thought that
>>passing a non const arg to a function with a const parameter was
>>generally not a problem, and indeed, VC++ didn't complain. What is
>>gcc's problem?
>>
>>
>
>There's discussion of this (that I didn't understand, but maybe you
>will) in the SUSv3 execv page, under Rationale, that implies that gcc
>is technically correct in having a problem. If you have to resort to
>ifdef hell, I'd make it check for mingw, not for __BORLANDC__, since
>mingw is what's getting the prototype wrong.
>
I didn't understand it either, and I don't understand your conclusion
that it implies gcc has a problem. Why did you think it implies that?
Are you suggesting that I should write
#ifdef __MINGW__
return execv(cmdname, argv);
#else
return execv(cmdname, (char *const *)argv);
#endif
? I can't see that that is an improvement because it now applies the
cast in the VC++ case too, which doesn't need a cast since it has the
correct prototype to start with.
The way I saw it is that it is Borland that gets the prototype wrong and
hence Borland that needs the cast.
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