AC_HEADER_STDC causes a compile failure with autoconf 2.70

From https://www.mail-archive.com/bug-autoconf@gnu.org/msg04408.html

> ... the long-obsolete AC_HEADER_STDC, previously used internally by
> AC_INCLUDES_DEFAULT, used AC_EGREP_HEADER.  The AC_HEADER_STDC macro
> is now a no-op (and is not used at all within Autoconf anymore), so
> that change is likely what made the first use of AC_EGREP_HEADER the
> one inside the if condition, causing the observed results.

The implication is that the test does nothing anyway, and due to it
being a no-op from 2.70 onwards, results in the required not being set
to yes, resulting in ./configure to fail.

Change-Id: Ic1ff38d87f791fbf1f2a80512f81bb7110392460
Signed-off-by: Jaco Kroon <jaco@uls.co.za>

configure

@@ -13129,122 +13129,6 @@ if test -z $ac_header_dirent -o "$ac_header_dirent" = "no"; then
   as_fn_error $? "*** Could not find dirent header that defines 'DIR'." "$LINENO" 5
 fi
 
-{ $as_echo "$as_me:${as_lineno-$LINENO}: checking for ANSI C header files" >&5
-$as_echo_n "checking for ANSI C header files... " >&6; }
-if ${ac_cv_header_stdc+:} false; then :
-  $as_echo_n "(cached) " >&6
-else
-  cat confdefs.h - <<_ACEOF >conftest.$ac_ext
-/* end confdefs.h.  */
-#include <stdlib.h>
-#include <stdarg.h>
-#include <string.h>
-#include <float.h>
-
-int
-main ()
-{
-
-  ;
-  return 0;
-}
-_ACEOF
-if ac_fn_c_try_compile "$LINENO"; then :
-  ac_cv_header_stdc=yes
-else
-  ac_cv_header_stdc=no
-fi
-rm -f core conftest.err conftest.$ac_objext conftest.$ac_ext
-
-if test $ac_cv_header_stdc = yes; then
-  # SunOS 4.x string.h does not declare mem*, contrary to ANSI.
-  cat confdefs.h - <<_ACEOF >conftest.$ac_ext
-/* end confdefs.h.  */
-#include <string.h>
-
-_ACEOF
-if (eval "$ac_cpp conftest.$ac_ext") 2>&5 |
-  $EGREP "memchr" >/dev/null 2>&1; then :
-
-else
-  ac_cv_header_stdc=no
-fi
-rm -f conftest*
-
-fi
-
-if test $ac_cv_header_stdc = yes; then
-  # ISC 2.0.2 stdlib.h does not declare free, contrary to ANSI.
-  cat confdefs.h - <<_ACEOF >conftest.$ac_ext
-/* end confdefs.h.  */
-#include <stdlib.h>
-
-_ACEOF
-if (eval "$ac_cpp conftest.$ac_ext") 2>&5 |
-  $EGREP "free" >/dev/null 2>&1; then :
-
-else
-  ac_cv_header_stdc=no
-fi
-rm -f conftest*
-
-fi
-
-if test $ac_cv_header_stdc = yes; then
-  # /bin/cc in Irix-4.0.5 gets non-ANSI ctype macros unless using -ansi.
-  if test "$cross_compiling" = yes; then :
-  :
-else
-  cat confdefs.h - <<_ACEOF >conftest.$ac_ext
-/* end confdefs.h.  */
-#include <ctype.h>
-#include <stdlib.h>
-#if ((' ' & 0x0FF) == 0x020)
-# define ISLOWER(c) ('a' <= (c) && (c) <= 'z')
-# define TOUPPER(c) (ISLOWER(c) ? 'A' + ((c) - 'a') : (c))
-#else
-# define ISLOWER(c) \
-		   (('a' <= (c) && (c) <= 'i') \
-		     || ('j' <= (c) && (c) <= 'r') \
-		     || ('s' <= (c) && (c) <= 'z'))
-# define TOUPPER(c) (ISLOWER(c) ? ((c) | 0x40) : (c))
-#endif
-
-#define XOR(e, f) (((e) && !(f)) || (!(e) && (f)))
-int
-main ()
-{
-  int i;
-  for (i = 0; i < 256; i++)
-    if (XOR (islower (i), ISLOWER (i))
-	|| toupper (i) != TOUPPER (i))
-      return 2;
-  return 0;
-}
-_ACEOF
-if ac_fn_c_try_run "$LINENO"; then :
-
-else
-  ac_cv_header_stdc=no
-fi
-rm -f core *.core core.conftest.* gmon.out bb.out conftest$ac_exeext \
-  conftest.$ac_objext conftest.beam conftest.$ac_ext
-fi
-
-fi
-fi
-{ $as_echo "$as_me:${as_lineno-$LINENO}: result: $ac_cv_header_stdc" >&5
-$as_echo "$ac_cv_header_stdc" >&6; }
-if test $ac_cv_header_stdc = yes; then
-
-$as_echo "#define STDC_HEADERS 1" >>confdefs.h
-
-fi
-
-if test "$ac_cv_header_stdc" != "yes"; then
-  as_fn_error $? "*** ANSI C header files not found." "$LINENO" 5
-fi
-
 { $as_echo "$as_me:${as_lineno-$LINENO}: checking for sys/wait.h that is POSIX.1 compatible" >&5
 $as_echo_n "checking for sys/wait.h that is POSIX.1 compatible... " >&6; }
 if ${ac_cv_header_sys_wait_h+:} false; then :

configure.ac

@@ -616,11 +616,6 @@ if test -z $ac_header_dirent -o "$ac_header_dirent" = "no"; then
   AC_MSG_ERROR([*** Could not find dirent header that defines 'DIR'.])
 fi
 
-AC_HEADER_STDC
-if test "$ac_cv_header_stdc" != "yes"; then
-  AC_MSG_ERROR([*** ANSI C header files not found.])
-fi
-
 AC_HEADER_SYS_WAIT
 if test "$ac_cv_header_sys_wait_h" != "yes"; then
   AC_MSG_ERROR([*** POSIX.1 compatible sys/wait.h is required.])