Re: documentation of AC_FUNC_ALLOCA and mingw-w64 compilers

[Bob Friesenhahn]

On Sun, 22 Jan 2012, Vincent Torri wrote:

> when using AC_FUNC_ALLOCA, the autoconf documentation says that one should 
> paste some code. That code generates a warning because:
>
> 1) the doc says to paste
>
> #elif defined __GNUC__
> # define alloca __builtin_alloca
>
> 2) the MinGW-w64 compiler already defines alloca in malloc.h, that header 
> files being included by stdlib.h because STDC_HEADERS is defined.
>
> I don't know how to properly fix the doc. One solution would be:
>
> #elif defined __GNUC__
> # ifndef alloca
> #  define alloca __builtin_alloca
> # endif
>
> what do you think ?

I think that your work-around is the safe approach and that the docs 
should be fixed.

Other build environments (e.g. Solaris 10) also use a similar macro 
definition and it becomes enabled by the compiler:

#define alloca(x)       __builtin_alloca(x)

Bob
--
Bob Friesenhahn
address@hidden, http://www.simplesystems.org/users/bfriesen/
GraphicsMagick Maintainer,    http://www.GraphicsMagick.org/