AC_PROG_CC_C99

[Roger Leigh]

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A new version of the proposed AC_PROG_CC_C99 macro follows.  It has
the following changes:

1. It puts the compiler into "C99 + extensions" mode in preference to
   "strict C99" mode, but will try both.
2. I added AIX CC support (but can't test it myself).


Regards,
Roger

# AC_PROG_CC_C99
# ----------------
# If the C compiler in not in ISO C99 C mode by default, try to add an
# option to output variable @code{CC} to make it so.  This macro tries
# various options that select ISO C99 C on some system or another.  It
# considers the compiler to be in ISO C99 C mode if it handles mixed
# code and declarations, _Bool, inline and restrict.
AC_DEFUN([AC_PROG_CC_C99],
[AC_MSG_CHECKING([for $CC option to accept ISO C99 C])
AC_CACHE_VAL(ac_cv_prog_cc_c99,
[ac_cv_prog_cc_c99=no
ac_save_CC=$CC
AC_LANG_CONFTEST([AC_LANG_PROGRAM(
[[#include <stdbool.h>
static inline int
test(const char *restrict text)
{
  int i = 0;
  // Iterate through items via the restricted pointer
  // and see if C++-style comments work.
  while (*(text+i) != '\0')
    ++i;
  return 0;
}]],
[[_Bool success = false;
  if (test("String literal") != 0)
    success = true;
  char *restrict newvar = "Another string";]])])
# Try
# GCC                   -std=gnu99 -std=c99 -std=iso9899:1999
# AIX                   -qlanglvl=extc99 -qlanglvl=stdc99
for ac_arg in "" -std=gnu99 -std=c99 -std=iso9899:1999 -qlanglvl=extc99 
-qlanglvl=stdc99
do
  CC="$ac_save_CC $ac_arg"
  _AC_COMPILE_IFELSE([],
                     [ac_cv_prog_cc_c99=$ac_arg
break])
done
rm -f conftest.$ac_ext conftest.$ac_objext
CC=$ac_save_CC
])
case "x$ac_cv_prog_cc_c99" in
  x|xno)
    AC_MSG_RESULT([none needed]) ;;
  *)
    AC_MSG_RESULT([$ac_cv_prog_cc_c99])
    CC="$CC $ac_cv_prog_cc_c99" ;;
esac
])# _AC_PROG_CC_C99

- -- 
Roger Leigh
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