Re: [PATCH 3/3] libctf: look for a qsort_r that functions properly

[Florian Weimer <fweimer at redhat dot com>]

* Nick Alcock:

> +AC_CACHE_CHECK([for qsort_r with arg last], ac_cv_libctf_qsort_r_arg_last,
> +[AC_RUN_IFELSE(
> +  [AC_LANG_PROGRAM(
> +  [#include <stdlib.h>
> +  int do_not_call (const void *a, const void *b, void *arg)
> +  {
> +    return (a < b);
> +  }
> +  static int works = 0;
> +  int conftest_compar (const void *a, const void *b, void *arg)
> +  {
> +    if (arg == do_not_call)
> +      works = 1;
> +    return (a < b);
> +  }
> +  int foo[[2]] = { 0, 1 };],
> +  [qsort_r (foo, 2, sizeof (int), conftest_compar, do_not_call);
> +   return (works == 0);])],
> +  [ac_cv_libctf_qsort_r_arg_last=yes],
> +  [ac_cv_libctf_qsort_r_arg_last=no],
> +  [ac_cv_libctf_qsort_r_arg_last=no])])

Can you use a compile test with the expected declaration, trying to
compile this?

#undef qsort_r
#include <stdlib.h>
void qsort_r (void *, size_t, size_t,
              int (*) (const void *, const void *, void *),
              void *);

And:

#undef qsort_r
#include <stdlib.h>
void qsort_r (void *, size_t, size_t, void *,
              int (*) (const void *, const void *, void *));

This will result in a hard compiler error, not just in an error.

Thanks,
Florian