AC_PROG_CC_NO_WRITEABLE_STRINGS(substvar [,hard])
, 

2005-01-25

Guido U. Draheim <guidod@gmx.de>

GPLWithACException
This program is free software; you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation. As a special exception, the respective Autoconf Macro's copyright owner gives unlimited permission to copy, distribute and modify the configure scripts that are the output of Autoconf when processing the Macro. You need not follow the terms of the GNU General Public License when using or distributing such scripts

guidod's Obsoleted (obsoleted)

• obsoleted Use AX_CFLAGS_NO_WRITABLE_STRINGS.

Try to find a compiler option that warns when a stringliteral is used in a place that could potentially modify the address. This should warn on giving an stringliteral to a function that asks of a non-const-modified char-pointer.

The sanity check is done by looking at string.h which has a set of strcpy definitions that should be defined with const-modifiers to not emit a warning in all so many places.

Currently this macro knows about GCC. hopefully will evolve to use: Solaris C compiler, Digital Unix C compiler, C for AIX Compiler, HP-UX C compiler, and IRIX C compiler.

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
])