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# ==================================================================================
# https://www.gnu.org/software/autoconf-archive/ax_cflags_no_writable_strings.html
# ==================================================================================
#
# SYNOPSIS
#
# AX_CFLAGS_NO_WRITABLE_STRINGS [(shellvar [,default, [A/NA]])]
#
# DESCRIPTION
#
# Try to find a compiler option that makes all string literals 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
#
# NOTE: These macros depend on AX_APPEND_FLAG.
#
# LICENSE
#
# Copyright (c) 2008 Guido U. Draheim <guidod@gmx.de>
#
# Copying and distribution of this file, with or without modification, are
# permitted in any medium without royalty provided the copyright notice
# and this notice are preserved. This file is offered as-is, without any
# warranty.
#serial 16
AC_DEFUN([AX_FLAGS_NO_WRITABLE_STRINGS],[dnl
AS_VAR_PUSHDEF([FLAGS],[_AC_LANG_PREFIX[]FLAGS])dnl
AS_VAR_PUSHDEF([VAR],[ax_cv_[]_AC_LANG_ABBREV[]flags_no_writable_strings])dnl
AC_CACHE_CHECK([m4_ifval([$1],[$1],FLAGS) making strings readonly],
VAR,[VAR="no, unknown"
ac_save_[]FLAGS="$[]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 "-pedantic -Werror % -fno-writable-strings -Wwrite-strings" dnl GCC
"-pedantic -Werror % -fconst-strings -Wwrite-strings" dnl newer GCC
"-pedantic % -fconst-strings %% no, const-strings is default" dnl newer 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_COMPILE_IFELSE([AC_LANG_PROGRAM([], [[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_COMPILE_IFELSE([AC_LANG_PROGRAM([[#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"
])
AS_VAR_POPDEF([FLAGS])dnl
AC_REQUIRE([AX_APPEND_FLAG])
case ".$VAR" in
.ok|.ok,*) m4_ifvaln($3,$3) ;;
.|.no|.no,*) m4_default($4,[m4_ifval($2,[AX_APPEND_FLAG([$2], [$1])])]) ;;
*) m4_default($3,[AX_APPEND_FLAG([$VAR], [$1])]) ;;
esac
AS_VAR_POPDEF([VAR])dnl
])dnl AX_FLAGS_NO_WRITABLE_STRINGS
AC_DEFUN([AX_CFLAGS_NO_WRITABLE_STRINGS],[dnl
AC_LANG_PUSH([C])
AX_FLAGS_NO_WRITABLE_STRINGS([$1], [$2], [$3], [$4])
AC_LANG_POP([C])
])
AC_DEFUN([AX_CXXFLAGS_NO_WRITABLE_STRINGS],[dnl
AC_LANG_PUSH([C++])
AX_FLAGS_NO_WRITABLE_STRINGS([$1], [$2], [$3], [$4])
AC_LANG_POP([C++])
])
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