Re: Fix an 8-year-old AC_REQUIRE bug

[Paolo Bonzini]

> But I am starting to agree with you that this particular version of the
> patch is too invasive, at least for 2.64.  It is flushing out real issues;
> for example, when used on coreutils, I noticed that the macro
> AC_PROG_GCC_TRADITIONAL invokes:
> if ...
>   AC_EGREP_CPP
> fi
> which, under the patch's new behavior, means that the check for egrep is
> no longer hoisted outside of the if unless I rewrite
> AC_PROG_GCC_TRADITIONAL to use AS_IF instead of raw if, or if I change it
> to use my new AC_REQUIRE_HOIST.

Indeed.

> So, I'm now starting to look at a different approach, using knowledge
> learned from the previous attempt.  If nothing else, I hope to at least be
> able to make autoconf warn when, during the course of a single outermost
> defun'd macro, another macro is first provided and later required.  That
> will be safe for 2.64, with no change in current ordering but adding a way
> to identify the problems.

Agreed.  The other part also seems to make sense, though I'm wary of
performance problems.

Paolo