Re: Messed up gl_COMPILER_PREPARE_CHECK_DECL

[Paul Eggert]

On 1/13/20 11:02 AM, Bruno Haible wrote:
> I would suggest that
> the particular 'case' and 'if'/'test' statements - or even the entire main body
> of the configure.ac, from line 130 to line 5588 - gets wrapped in an AC_DEFUN
> that gets invoked once.

Thanks for the diagnosis. I came up with a simpler patch to Emacs, and 
installed it into Emacs master (attached).

This patch doesn't solve the general problem, just this particular case. 
I doubt whether our collection of Emacs hackers can be induced to 
remember that the Autoconf macros you mentioned cannot be executed 
inside a shell condition, and I wouldn't be surprised if other configure 
scripts run into similar problems. I don't have any specific suggestion 
to work around this problem in Gnulib, though.

PS. I vaguely recall a long discussion many years ago when we added this 
AC_REQUIRE-ish stuff to Autoconf. Although we did fix some major 
glitches, we replacing them with other glitches that live on to this 
day. For example, there's now this note in the Autoconf manual:

     Many Autoconf macros use a compiler, and thus call
     `AC_REQUIRE([AC_PROG_CC])' to ensure that the compiler has been
     determined before the body of the outermost `AC_DEFUN' macro.
     Although `AC_PROG_CC' is safe to directly expand multiple times, it
     performs certain checks (such as the proper value of `EXEEXT') only
     on the first invocation.  Therefore, care must be used when
     invoking this macro from within another macro rather than at the
     top level (*note Expanded Before Required::).

all of which I had forgotten until I read your email today.

0001-Port-configure.ac-to-future-Gnulib.patch
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