Try to find a compiler option that makes all stringliteral
readonly.
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.
For the GNU CC compiler it will be -fno-writable-strings
-Wwrite-strings The result is added to the shellvar being CFLAGS by
default.
DEFAULTS:
- $1 shell-variable-to-add-to : CFLAGS
- $2 add-value-if-not-found : nothing
- $3 action-if-found : add value to shellvariable
- $4 action-if-not-found : nothing
AC_DEFUN([AX_CFLAGS_NO_WRITABLE_STRINGS],[dnl
AS_VAR_PUSHDEF([FLAGS],[CFLAGS])dnl
AS_VAR_PUSHDEF([VAR],[ac_cv_cflags_no_writable_strings])dnl
AC_CACHE_CHECK([m4_ifval([$1],[$1],FLAGS) making strings readonly],
VAR,[VAR="no, unknown"
AC_LANG_SAVE
AC_LANG_C
ac_save_[]FLAGS="$[]FLAGS"
# 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. - guidod
for ac_arg dnl
in "-Wall % -fno-writable-strings -Wwrite-strings" dnl GCC
"-v -Xc % -xstrconst" dnl Solaris C - strings go into readonly segment
"+w1 -Aa % +ESlit" dnl HP-UX C - strings go into readonly segment
"-w0 -std1 % -readonly_strings" dnl Digital Unix - again readonly segment
"-fullwarn -use_readonly_const %% ok, its the default" dnl IRIX C
#
do FLAGS="$ac_save_[]FLAGS "`echo $ac_arg | sed -e 's,%%.*,,' -e 's,%,,'`
AC_TRY_COMPILE([],[return 0;],
[VAR=`echo $ac_arg | sed -e 's,.*% *,,'` ; break])
done
case ".$VAR" in
.|.no|.no,*) ;;
*) # sanity check - testing strcpy() from string.h
cp config.log config.tmp
AC_TRY_COMPILE([#include <string.h>],[
char test[16];
if (strcpy (test, "test")) return 1;],
dnl the original did use test -n `$CC testprogram.c`
[if test `diff config.log config.tmp | grep -i warning | wc -l` != 0
then VAR="no, suppressed, string.h," ; fi],
[VAR="no, suppressed, string.h"])
rm config.tmp
;;
esac
FLAGS="$ac_save_[]FLAGS"
AC_LANG_RESTORE
])
case ".$VAR" in
.ok|.ok,*) m4_ifvaln($3,$3) ;;
.|.no|.no,*) m4_ifvaln($4,$4,[m4_ifval($2,[
AC_RUN_LOG([: m4_ifval($1,$1,FLAGS)="$m4_ifval($1,$1,FLAGS) $2"])
m4_ifval($1,$1,FLAGS)="$m4_ifval($1,$1,FLAGS) $2"])]) ;;
*) m4_ifvaln($3,$3,[
if echo " $[]m4_ifval($1,$1,FLAGS) " | grep " $VAR " 2>&1 >/dev/null
then AC_RUN_LOG([: m4_ifval($1,$1,FLAGS) does contain $VAR])
else AC_RUN_LOG([: m4_ifval($1,$1,FLAGS)="$m4_ifval($1,$1,FLAGS) $VAR"])
m4_ifval($1,$1,FLAGS)="$m4_ifval($1,$1,FLAGS) $VAR"
fi ]) ;;
esac
AS_VAR_POPDEF([VAR])dnl
AS_VAR_POPDEF([FLAGS])dnl
])
dnl the only difference - the LANG selection... and the default FLAGS
AC_DEFUN([AX_CXXFLAGS_NO_WRITABLE_STRINGS],[dnl
AS_VAR_PUSHDEF([FLAGS],[CXXFLAGS])dnl
AS_VAR_PUSHDEF([VAR],[ac_cv_cxxflags_no_writable_strings])dnl
AC_CACHE_CHECK([m4_ifval($1,$1,FLAGS) making strings readonly],
VAR,[VAR="no, unknown"
AC_LANG_SAVE
AC_LANG_CXX
ac_save_[]FLAGS="$[]FLAGS"
# 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. - guidod
for ac_arg dnl
in "-Wall % -fno-writable-strings -Wwrite-strings" dnl GCC
"-v -Xc % -xstrconst" dnl Solaris C - strings go into readonly segment
"+w1 -Aa % +ESlit" dnl HP-UX C - strings go into readonly segment
"-w0 -std1 % -readonly_strings" dnl Digital Unix - again readonly segment
"-fullwarn -use_readonly_const %% ok, its the default" dnl IRIX C
#
do FLAGS="$ac_save_[]FLAGS "`echo $ac_arg | sed -e 's,%%.*,,' -e 's,%,,'`
AC_TRY_COMPILE([],[return 0;],
[VAR=`echo $ac_arg | sed -e 's,.*% *,,'` ; break])
done
case ".$VAR" in
.|.no|.no,*) ;;
*) # sanity check - testing strcpy() from string.h
cp config.log config.tmp
AC_TRY_COMPILE([#include <string.h>],[[
char test[16];
if (strcpy (test, "test")) return 1;]],
dnl the original did use test -n `$CC testprogram.c`
[if test `diff config.log config.tmp | grep -i warning | wc -l` != 0
then VAR="no, suppressed, string.h," ; fi],
[VAR="no, suppressed, string.h"])
rm config.tmp
;;
esac
FLAGS="$ac_save_[]FLAGS"
AC_LANG_RESTORE
])
case ".$VAR" in
.ok|.ok,*) m4_ifvaln($3,$3) ;;
.|.no|.no,*) m4_ifvaln($4,$4,[m4_ifval($2,[
AC_RUN_LOG([: m4_ifval($1,$1,FLAGS)="$m4_ifval($1,$1,FLAGS) $VAR"])
m4_ifval($1,$1,FLAGS)="$m4_ifval($1,$1,FLAGS) $2"])]) ;;
*) m4_ifvaln($3,$3,[
if echo " $[]m4_ifval($1,$1,FLAGS) " | grep " $VAR " 2>&1 >/dev/null
then AC_RUN_LOG([: m4_ifval($1,$1,FLAGS) does contain $VAR])
else AC_RUN_LOG([: m4_ifval($1,$1,FLAGS)="$m4_ifval($1,$1,FLAGS) $VAR"])
m4_ifval($1,$1,FLAGS)="$m4_ifval($1,$1,FLAGS) $VAR"
fi ]) ;;
esac
AS_VAR_POPDEF([VAR])dnl
AS_VAR_POPDEF([FLAGS])dnl
])