Here's a proposed patch to the stdarg module description, to describe the benefits of using AC_PROG_CC_STDC with this module.
2007-02-04 Paul Eggert <[EMAIL PROTECTED]> * modules/stdarg (configure.ac): Add comment suggestiong AC_PROG_CC_STDC. --- modules/stdarg.~1.1.~ 2006-05-08 06:13:13.000000000 -0700 +++ modules/stdarg 2007-02-04 09:39:15.000000000 -0800 @@ -7,6 +7,12 @@ m4/stdarg.m4 Depends-on: configure.ac: +dnl AC_PROG_CC_STDC should be added quite early to configure.ac. +dnl Some compilers (e.g., AIX 5.3 cc) need to be in c99 mode +dnl for the builtin va_copy to work. With Autoconf 2.60 or later, +dnl AC_PROG_CC_STDC arranges for this. With older Autoconf AC_PROG_CC_STDC +dnl shouldn't hurt, though installers are on their own to set c99 mode. +dnl gl_STDARG_H Makefile.am: