Re: alloca.h example in the manual

[Eric Blake]

On 09/07/2010 12:55 PM, Giorgos Keramidas wrote:
> Hi all,
>
> The Autoconf manual (section 5.5.2, "Particular Function Checks")
> recommends the following check for source files that use the alloca()
> function:

Which version of the manual are you looking at?  This issue was recently 
reported; are there still issues beyond what was mentioned in this thread?

http://lists.gnu.org/archive/html/bug-autoconf/2010-08/msg00035.html

In particular, could you demonstrate an actual sample program and 
compiler output that backs up your point, as requested in:
http://lists.gnu.org/archive/html/bug-autoconf/2010-08/msg00042.html

> The modified version shown below declares a prototype of alloca() only
> when HAVE_ALLOCA is unset/undefined regardless of what HAVE_ALLOCA_H is
> set to:
>
>      #ifdef HAVE_ALLOCA_H
>      # include<alloca.h>
>      #elif !defined(HAVE_ALLOCA)
>      # if defined __GNUC__
>      #  define alloca __builtin_alloca
>      # elif defined _AIX
>      #  define alloca __alloca
>      # else
>      #  include<stddef.h>
>      #  ifdef  __cplusplus
>      extern "C"
>      #  endif
>      void *alloca (size_t);
>      # endif
>      #endif

Then again, since AC_FUNC_ALLOCA does indeed set HAVE_ALLOCA via 
AC_DEFINE, your patch proposal probably makes sense.

--
Eric Blake   address@hidden    +1-801-349-2682
Libvirt virtualization library http://libvirt.org