Re: AS_IF

[Bruno Haible]

Hi Paul,

> The third patch merely streamlines 'configure' when running on platforms like 
> Solaris that need not use libsigsegv.
> 
> -   if test "$gl_cv_lib_sigsegv" = yes \
> -       && test "$gl_cv_sys_xsi_stack_overflow_heuristic" != yes; then
> -     AC_SUBST([LIBCSTACK], [$LIBSIGSEGV])
> -     AC_SUBST([LTLIBCSTACK], [$LTLIBSIGSEGV])
> -   fi
> +   AS_IF([test "$gl_cv_sys_xsi_stack_overflow_heuristic" != yes],
> +     [gl_LIBSIGSEGV
> +      AS_IF([test "$gl_cv_lib_sigsegv" = yes],
> +        [AC_SUBST([LIBCSTACK], [$LIBSIGSEGV])
> +         AC_SUBST([LTLIBCSTACK], [$LTLIBSIGSEGV])])])

Any particular reason why AS_IF is used here?

I typically don't use AS_IF because
  - I find a line of shell code more readable than a mix between m4 syntax
    and shell syntax,
  - it's yet another step in the learning curve, for someone who wants to
    understand how Autoconf macros work.

The Autoconf documentation says
  AS_IF "ensures any required macros ... are expanded before
  the first test."
AFAICS, this is relevant for code written directly into configure.ac. But
inside an AC_DEFUN it is irrelevant, because required macros are hoisted
before the body of the AC_DEFUN anyway.

Bruno