Re: document a surprising behaviour of macros AC_PROG_{CC,CXX,F77}

[Ralf Wildenhues]

Hi Stefano,

thanks for the patch, and sorry for the delay on this.

* Stefano Lattarini wrote on Sun, Feb 28, 2010 at 03:25:09PM CET:
> This topic came up a while ago on bug-autoconf, but the patch I posted 
> there went unnoticed or was ignored.

Well, I put it off for later because the right thing to do here would be
to also add a set of AC_PROG_{CC,...}_WORKS macros that people can then
use.  Also, a statement like this:

> This behaviour may seem
> +surprising, but probably it cannot be fixed without breaking backward
> +compatibility in some way.

states "we've given up on this", whereas the reason I've put it off was
"I haven't done enough research to know for sure whether we can safely
change semantics".

The use of AC_REQUIRE tends to require us to provide macros which do not
take arguments in the vast number of default uses, so that we can easily
let them be required.  Adding options IF-FAILS arguments to the
AC_PROG_{CC,...} macros is bad because some of them already have
optional arguments, some used to have them, and they are often
AC_REQUIREd without options.

IOW, I'd prefer to not promise anything now which we may be able to fix
in a better way later.

Cheers,
Ralf