dnl @synopsis AC_PROG_CC_NO_WRITEABLE_STRINGS(substvar [,hard])
dnl
dnl Try to find a compiler option that warns when a stringliteral is
dnl used in a place that could potentially modify the address. This
dnl should warn on giving an stringliteral to a function that asks of
dnl a non-const-modified char-pointer.
dnl
dnl The sanity check is done by looking at string.h which has a set
dnl of strcpy definitions that should be defined with const-modifiers
dnl to not emit a warning in all so many places.
dnl
dnl Currently this macro knows about GCC.
dnl hopefully will evolve to use:    Solaris C compiler,
dnl Digital Unix C compiler, C for AIX Compiler, HP-UX C compiler,
dnl and IRIX C compiler.
dnl
dnl @version $Id: ac_prog_cc_no_writeable_strings.m4,v 1.1 2002/02/20 16:18:18 steve Exp $
dnl @author Guido Draheim <guidod@gmx.de>
dnl
AC_DEFUN([AC_PROG_CC_NO_WRITEABLE_STRINGS], [
  pushdef([CV],ac_cv_prog_cc_no_writeable_strings)dnl
  hard=$2
  if test -z "$hard"; then
    msg="C to warn about writing to stringliterals"
  else
    msg="C to prohibit any write to stringliterals"
  fi
  AC_CACHE_CHECK($msg, CV, [
  cat > conftest.c <<EOF
#include <string.h>
int main (void)
{
   char test[[16]];
   if (strcpy (test, "test")) return 0;
   return 1;
}
EOF
  dnl GCC
  if test "$GCC" = "yes"; 
  then
  	if test -z "$hard"; then
      	    CV="-Wwrite-strings"
        else
            CV="-fno-writable-strings -Wwrite-strings"
        fi

        if test -n "`${CC-cc} -c $CV conftest.c 2>&1`" ; then
            CV="suppressed: string.h"
        fi

  dnl Solaris C compiler
  elif  $CC -flags 2>&1 | grep "Xc.*strict ANSI C" > /dev/null 2>&1 &&
	$CC -c -xstrconst conftest.c > /dev/null 2>&1 &&
	test -f conftest.o 
  then
        # strings go into readonly segment
	CV="-xstrconst"

	rm conftest.o
        if test -n "`${CC-cc} -c $CV conftest.c 2>&1`" ; then
             CV="suppressed: string.h"
        fi
  
  dnl HP-UX C compiler
  elif  $CC > /dev/null 2>&1 &&
	$CC -c +ESlit conftest.c > /dev/null 2>&1 &&
	test -f conftest.o 
  then
       # strings go into readonly segment
	CV="+ESlit"
	
	rm conftest.o
        if test -n "`${CC-cc} -c $CV conftest.c 2>&1`" ; then
             CV="suppressed: string.h"
        fi

  dnl Digital Unix C compiler
  elif ! $CC > /dev/null 2>&1 &&
	$CC -c -readonly_strings conftest.c > /dev/null 2>&1 &&
	test -f conftest.o
  then	
       # strings go into readonly segment
	CV="-readonly_strings"
	
	rm conftest.o
        if test -n "`${CC-cc} -c $CV conftest.c 2>&1`" ; then
             CV="suppressed: string.h"
        fi

  dnl C for AIX Compiler

  dnl IRIX C compiler
	# -use_readonly_const is the default for IRIX C, 
	# puts them into .rodata, but they are copied later.
	# need to be "-G0 -rdatashared" for strictmode but
	# I am not sure what effect that has really.

  fi
  rm -f conftest.*
  ])
  if test -z "[$]$1" ; then
    if test -n "$CV" ; then
      case "$CV" in
        suppressed*) $1="" ;; # known but suppressed
        *)  $1="$CV" ;;
      esac
    fi
  fi
  AC_SUBST($1)
  popdef([CV])dnl
])