]> git.ipfire.org Git - thirdparty/cups.git/blobdiff - config-scripts/cups-compiler.m4
Merge pull request #5621 from zdohnal/cgigetarray-sigsegv
[thirdparty/cups.git] / config-scripts / cups-compiler.m4
index fc1c821eae97ccb2161ed9324fdf47049aab2936..63ea1f47010fa67764eb1d7b1fdb186ce59cc0d1 100644 (file)
@@ -1,63 +1,88 @@
 dnl
-dnl "$Id: cups-compiler.m4 6975 2007-09-18 20:37:09Z mike $"
+dnl Compiler stuff for CUPS.
 dnl
-dnl   Compiler stuff for the Common UNIX Printing System (CUPS).
+dnl Copyright 2007-2018 by Apple Inc.
+dnl Copyright 1997-2007 by Easy Software Products, all rights reserved.
 dnl
-dnl   Copyright 2007-2008 by Apple Inc.
-dnl   Copyright 1997-2007 by Easy Software Products, all rights reserved.
-dnl
-dnl   These coded instructions, statements, and computer programs are the
-dnl   property of Apple Inc. and are protected by Federal copyright
-dnl   law.  Distribution and use rights are outlined in the file "LICENSE.txt"
-dnl   which should have been included with this file.  If this file is
-dnl   file is missing or damaged, see the license at "http://www.cups.org/".
+dnl Licensed under Apache License v2.0.  See the file "LICENSE" for more information.
 dnl
 
 dnl Clear the debugging and non-shared library options unless the user asks
 dnl for them...
-OPTIM=""
+INSTALL_STRIP=""
+AC_SUBST(INSTALL_STRIP)
+
+AC_ARG_WITH(optim, [  --with-optim            set optimization flags ],
+       OPTIM="$withval",
+       OPTIM="")
 AC_SUBST(OPTIM)
 
-AC_ARG_WITH(optim, [  --with-optim="flags"    set optimization flags ])
-AC_ARG_ENABLE(debug, [  --enable-debug          turn on debugging, default=no],
-       [if test x$enable_debug = xyes; then
-               OPTIM="-g"
-       fi])
+AC_ARG_ENABLE(debug, [  --enable-debug          build with debugging symbols])
+AC_ARG_ENABLE(debug_guards, [  --enable-debug-guards   build with memory allocation guards])
+AC_ARG_ENABLE(debug_printfs, [  --enable-debug-printfs  build with CUPS_DEBUG_LOG support])
+AC_ARG_ENABLE(unit_tests, [  --enable-unit-tests     build and run unit tests])
+
+dnl For debugging, keep symbols, otherwise strip them...
+if test x$enable_debug = xyes -a "x$OPTIM" = x; then
+       OPTIM="-g"
+else
+       INSTALL_STRIP="-s"
+fi
+
+dnl Debug printfs can slow things down, so provide a separate option for that
+if test x$enable_debug_printfs = xyes; then
+       CFLAGS="$CFLAGS -DDEBUG"
+       CXXFLAGS="$CXXFLAGS -DDEBUG"
+fi
+
+dnl Debug guards use an extra 4 bytes for some structures like strings in the
+dnl string pool, so provide a separate option for that
+if test x$enable_debug_guards = xyes; then
+       CFLAGS="$CFLAGS -DDEBUG_GUARDS"
+       CXXFLAGS="$CXXFLAGS -DDEBUG_GUARDS"
+fi
+
+dnl Unit tests take up time during a compile...
+if test x$enable_unit_tests = xyes; then
+        if test "$build" != "$host"; then
+                AC_MSG_ERROR([Sorry, cannot build unit tests when cross-compiling.])
+        fi
+
+       UNITTESTS="unittests"
+else
+       UNITTESTS=""
+fi
+AC_SUBST(UNITTESTS)
 
 dnl Setup general architecture flags...
-AC_ARG_WITH(archflags, [  --with-archflags="flags"
-                          set default architecture flags ])
+AC_ARG_WITH(archflags, [  --with-archflags        set default architecture flags ])
+AC_ARG_WITH(ldarchflags, [  --with-ldarchflags      set program architecture flags ])
 
 if test -z "$with_archflags"; then
        ARCHFLAGS=""
-       LDARCHFLAGS=""
 else
        ARCHFLAGS="$with_archflags"
-       if test "$uname" = Darwin; then
-               # Only link 32-bit programs - 64-bit is for the shared
-               # libraries...
-               LDARCHFLAGS="`echo $ARCHFLAGS | sed -e '1,$s/-arch x86_64//' -e '1,$s/-arch ppc64//'`"
+fi
+
+if test -z "$with_ldarchflags"; then
+       if test "$host_os_name" = darwin; then
+               # Only create Intel programs by default
+               LDARCHFLAGS="`echo $ARCHFLAGS | sed -e '1,$s/-arch ppc64//'`"
        else
                LDARCHFLAGS="$ARCHFLAGS"
        fi
+else
+       LDARCHFLAGS="$with_ldarchflags"
 fi
 
 AC_SUBST(ARCHFLAGS)
 AC_SUBST(LDARCHFLAGS)
 
-dnl Setup support for separate 32/64-bit library generation...
-AC_ARG_WITH(arch32flags, [  --with-arch32flags="flags"
-                          specifies 32-bit architecture flags])
-ARCH32FLAGS=""
-AC_SUBST(ARCH32FLAGS)
-
-AC_ARG_WITH(arch64flags, [  --with-arch64flags="flags"
-                          specifies 64-bit architecture flags])
-ARCH64FLAGS=""
-AC_SUBST(ARCH64FLAGS)
-
 dnl Read-only data/program support on Linux...
-AC_ARG_ENABLE(relro, [  --enable-relro          use GCC relro option, default=no])
+AC_ARG_ENABLE(relro, [  --enable-relro          build with the GCC relro option])
+
+dnl Clang/GCC address sanitizer...
+AC_ARG_ENABLE(sanitizer, [  --enable-sanitizer      build with AddressSanitizer])
 
 dnl Update compiler options...
 CXXLIBS="${CXXLIBS:=}"
@@ -69,411 +94,105 @@ AC_SUBST(PIEFLAGS)
 RELROFLAGS=""
 AC_SUBST(RELROFLAGS)
 
-LIBCUPSORDER="libcups.order"
-AC_ARG_WITH(libcupsorder, [  --with-libcupsorder     libcups secorder file, default=libcups.order],
-       if test -f "$withval"; then
-               LIBCUPSORDER="$withval"
-       fi)
-AC_SUBST(LIBCUPSORDER)
-
-LIBCUPSIMAGEORDER="libcupsimage.order"
-AC_ARG_WITH(libcupsimageorder, [  --with-libcupsimagesorder
-                          libcupsimage secorder file, default=libcupsimage.order],
-       if test -f "$withval"; then
-               LIBCUPSIMAGEORDER="$withval"
-       fi)
-AC_SUBST(LIBCUPSIMAGEORDER)
+WARNING_OPTIONS=""
+AC_SUBST(WARNING_OPTIONS)
 
 if test -n "$GCC"; then
        # Add GCC-specific compiler options...
+
+        # Address sanitizer is a useful tool to use when developing/debugging
+        # code but adds about 2x overhead...
+       if test x$enable_sanitizer = xyes; then
+               # Use -fsanitize=address with debugging...
+               OPTIM="$OPTIM -g -fsanitize=address"
+       else
+               # Otherwise use the Fortify enhancements to catch any unbounded
+               # string operations...
+               CFLAGS="$CFLAGS -D_FORTIFY_SOURCE=2"
+               CXXFLAGS="$CXXFLAGS -D_FORTIFY_SOURCE=2"
+       fi
+
+       # Default optimization options...
        if test -z "$OPTIM"; then
-               if test "x$with_optim" = x; then
-                       # Default to optimize-for-size and debug
-                               OPTIM="-Os -g"
-               else
-                       OPTIM="$with_optim $OPTIM"
-               fi
+               # Default to optimize-for-size and debug
+               OPTIM="-Os -g"
        fi
 
        # Generate position-independent code as needed...
-       if test $PICFLAG = 1 -a $uname != AIX; then
+       if test $PICFLAG = 1; then
                OPTIM="-fPIC $OPTIM"
        fi
 
        # The -fstack-protector option is available with some versions of
        # GCC and adds "stack canaries" which detect when the return address
        # has been overwritten, preventing many types of exploit attacks.
-       AC_MSG_CHECKING(if GCC supports -fstack-protector)
+       AC_MSG_CHECKING(whether compiler supports -fstack-protector)
        OLDCFLAGS="$CFLAGS"
        CFLAGS="$CFLAGS -fstack-protector"
-       AC_TRY_COMPILE(,,
-               OPTIM="$OPTIM -fstack-protector"
-               AC_MSG_RESULT(yes),
-               AC_MSG_RESULT(no))
-       CFLAGS="$OLDCFLAGS"
-
-       # The -pie option is available with some versions of GCC and adds
-       # randomization of addresses, which avoids another class of exploits
-       # that depend on a fixed address for common functions.
-       AC_MSG_CHECKING(if GCC supports -pie)
-       OLDCFLAGS="$CFLAGS"
-       CFLAGS="$CFLAGS -pie -fPIE"
-       AC_TRY_COMPILE(,,
-               PIEFLAGS="-pie -fPIE"
+       AC_TRY_LINK(,,
+               if test "x$LSB_BUILD" = xy; then
+                       # Can't use stack-protector with LSB binaries...
+                       OPTIM="$OPTIM -fno-stack-protector"
+               else
+                       OPTIM="$OPTIM -fstack-protector"
+               fi
                AC_MSG_RESULT(yes),
                AC_MSG_RESULT(no))
        CFLAGS="$OLDCFLAGS"
 
-       if test "x$with_optim" = x; then
-               # Add useful warning options for tracking down problems...
-               OPTIM="-Wall -Wno-format-y2k $OPTIM"
-               # Additional warning options for development testing...
-               if test -d .svn; then
-                       OPTIM="-Wshadow -Wunused $OPTIM"
-               fi
+       if test "x$LSB_BUILD" != xy; then
+               # The -fPIE option is available with some versions of GCC and
+               # adds randomization of addresses, which avoids another class of
+               # exploits that depend on a fixed address for common functions.
+               #
+               # Not available to LSB binaries...
+               AC_MSG_CHECKING(whether compiler supports -fPIE)
+               OLDCFLAGS="$CFLAGS"
+               case "$host_os_name" in
+                       darwin*)
+                               CFLAGS="$CFLAGS -fPIE -Wl,-pie"
+                               AC_TRY_COMPILE(,,[
+                                       PIEFLAGS="-fPIE -Wl,-pie"
+                                       AC_MSG_RESULT(yes)],
+                                       AC_MSG_RESULT(no))
+                               ;;
+
+                       *)
+                               CFLAGS="$CFLAGS -fPIE -pie"
+                               AC_TRY_COMPILE(,,[
+                                       PIEFLAGS="-fPIE -pie"
+                                       AC_MSG_RESULT(yes)],
+                                       AC_MSG_RESULT(no))
+                               ;;
+               esac
+               CFLAGS="$OLDCFLAGS"
        fi
 
-       case "$uname" in
-               Darwin*)
-                       # -D_FORTIFY_SOURCE=2 adds additional object size
-                       # checking, basically wrapping all string functions
-                       # with buffer-limited ones.  Not strictly needed for
-                       # CUPS since we already use buffer-limited calls, but
-                       # this will catch any additions that are broken.                
-                       CFLAGS="$CFLAGS -D_FORTIFY_SOURCE=2"
-                       ;;
-
-               HP-UX*)
-                       if test "x$enable_32bit" = xyes; then
-                               # Build 32-bit libraries, 64-bit base...
-                               if test -z "$with_arch32flags"; then
-                                       ARCH32FLAGS="-milp32"
-                               else
-                                       ARCH32FLAGS="$with_arch32flags"
-                               fi
+       # Add useful warning options for tracking down problems...
+       WARNING_OPTIONS="-Wall -Wno-format-y2k -Wunused -Wno-unused-result -Wsign-conversion"
 
-                               if test -z "$with_archflags"; then
-                                       if test -z "$with_arch64flags"; then
-                                               ARCHFLAGS="-mlp64"
-                                       else
-                                               ARCHFLAGS="$with_arch64flags"
-                                       fi
-                               fi
-                       fi
-
-                       if test "x$enable_64bit" = xyes; then
-                               # Build 64-bit libraries, 32-bit base...
-                               if test -z "$with_arch64flags"; then
-                                       ARCH64FLAGS="-mlp64"
-                               else
-                                       ARCH64FLAGS="$with_arch64flags"
-                               fi
-
-                               if test -z "$with_archflags"; then
-                                       if test -z "$with_arch32flags"; then
-                                               ARCHFLAGS="-milp32"
-                                       else
-                                               ARCHFLAGS="$with_arch32flags"
-                                       fi
-                               fi
-                       fi
+       # Test GCC version for certain warning flags since -Werror
+       # doesn't trigger...
+       gccversion=`$CC --version | head -1 | awk '{print $NF}'`
+       case "$gccversion" in
+               1.* | 2.* | 3.* | 4.* | 5.* | 6.* | \(clang-*)
                        ;;
-
-               IRIX)
-                       if test "x$enable_32bit" = xyes; then
-                               # Build 32-bit libraries, 64-bit base...
-                               if test -z "$with_arch32flags"; then
-                                       ARCH32FLAGS="-n32 -mips3"
-                               else
-                                       ARCH32FLAGS="$with_arch32flags"
-                               fi
-
-                               if test -z "$with_archflags"; then
-                                       if test -z "$with_arch64flags"; then
-                                               ARCHFLAGS="-64 -mips4"
-                                       else
-                                               ARCHFLAGS="$with_arch64flags"
-                                       fi
-                               fi
-                       fi
-
-                       if test "x$enable_64bit" = xyes; then
-                               # Build 64-bit libraries, 32-bit base...
-                               if test -z "$with_arch64flags"; then
-                                       ARCH64FLAGS="-64 -mips4"
-                               else
-                                       ARCH64FLAGS="$with_arch64flags"
-                               fi
-
-                               if test -z "$with_archflags"; then
-                                       if test -z "$with_arch32flags"; then
-                                               ARCHFLAGS="-n32 -mips3"
-                                       else
-                                               ARCHFLAGS="$with_arch32flags"
-                                       fi
-                               fi
-                       fi
-                       ;;
-
-               Linux*)
-                       # The -z relro option is provided by the Linux linker command to
-                       # make relocatable data read-only.
-                       if test x$enable_relro = xyes; then
-                               RELROFLAGS="-Wl,-z,relro"
-                       fi
-
-                       if test "x$enable_32bit" = xyes; then
-                               # Build 32-bit libraries, 64-bit base...
-                               if test -z "$with_arch32flags"; then
-                                       ARCH32FLAGS="-m32"
-                               else
-                                       ARCH32FLAGS="$with_arch32flags"
-                               fi
-
-                               if test -z "$with_archflags"; then
-                                       if test -z "$with_arch64flags"; then
-                                               ARCHFLAGS="-m64"
-                                       else
-                                               ARCHFLAGS="$with_arch64flags"
-                                       fi
-                               fi
-                       fi
-
-                       if test "x$enable_64bit" = xyes; then
-                               # Build 64-bit libraries, 32-bit base...
-                               if test -z "$with_arch64flags"; then
-                                       ARCH64FLAGS="-m64"
-                               else
-                                       ARCH64FLAGS="$with_arch64flags"
-                               fi
-
-                               if test -z "$with_archflags"; then
-                                       if test -z "$with_arch32flags"; then
-                                               ARCHFLAGS="-m32"
-                                       else
-                                               ARCHFLAGS="$with_arch32flags"
-                                       fi
-                               fi
-                       fi
-                       ;;
-
-               SunOS*)
-                       if test "x$enable_32bit" = xyes; then
-                               # Build 32-bit libraries, 64-bit base...
-                               if test -z "$with_arch32flags"; then
-                                       ARCH32FLAGS="-m32"
-                               else
-                                       ARCH32FLAGS="$with_arch32flags"
-                               fi
-
-                               if test -z "$with_archflags"; then
-                                       if test -z "$with_arch64flags"; then
-                                               ARCHFLAGS="-m64"
-                                       else
-                                               ARCHFLAGS="$with_arch64flags"
-                                       fi
-                               fi
-                       fi
-
-                       if test "x$enable_64bit" = xyes; then
-                               # Build 64-bit libraries, 32-bit base...
-                               if test -z "$with_arch64flags"; then
-                                       ARCH64FLAGS="-m64"
-                               else
-                                       ARCH64FLAGS="$with_arch64flags"
-                               fi
-
-                               if test -z "$with_archflags"; then
-                                       if test -z "$with_arch32flags"; then
-                                               ARCHFLAGS="-m32"
-                                       else
-                                               ARCHFLAGS="$with_arch32flags"
-                                       fi
-                               fi
-                       fi
+               *)
+                       WARNING_OPTIONS="$WARNING_OPTIONS -Wno-format-truncation -Wno-format-overflow -Wno-tautological-compare"
                        ;;
        esac
+
+       # Additional warning options for development testing...
+       if test -d .git; then
+               WARNING_OPTIONS="-Werror -Wno-error=deprecated-declarations $WARNING_OPTIONS"
+       fi
 else
        # Add vendor-specific compiler options...
-       case $uname in
-               AIX*)
-                       if test -z "$OPTIM"; then
-                               if test "x$with_optim" = x; then
-                                       OPTIM="-O2 -qmaxmem=6000"
-                               else
-                                       OPTIM="$with_optim $OPTIM"
-                               fi
-                       fi
-                       ;;
-               HP-UX*)
-                       if test -z "$OPTIM"; then
-                               if test "x$with_optim" = x; then
-                                       OPTIM="+O2"
-                               else
-                                       OPTIM="$with_optim $OPTIM"
-                               fi
-                       fi
-
-                       CFLAGS="-Ae $CFLAGS"
-
-                       if test $PICFLAG = 1; then
-                               OPTIM="+z $OPTIM"
-                       fi
-
-                       if test "x$enable_32bit" = xyes; then
-                               # Build 32-bit libraries, 64-bit base...
-                               if test -z "$with_arch32flags"; then
-                                       ARCH32FLAGS="+DD32"
-                               else
-                                       ARCH32FLAGS="$with_arch32flags"
-                               fi
-
-                               if test -z "$with_archflags"; then
-                                       if test -z "$with_arch64flags"; then
-                                               ARCHFLAGS="+DD64"
-                                       else
-                                               ARCHFLAGS="$with_arch64flags"
-                                       fi
-                               fi
-                       fi
-
-                       if test "x$enable_64bit" = xyes; then
-                               # Build 64-bit libraries, 32-bit base...
-                               if test -z "$with_arch64flags"; then
-                                       ARCH64FLAGS="+DD64"
-                               else
-                                       ARCH64FLAGS="$with_arch64flags"
-                               fi
-
-                               if test -z "$with_archflags"; then
-                                       if test -z "$with_arch32flags"; then
-                                               ARCHFLAGS="+DD32"
-                                       else
-                                               ARCHFLAGS="$with_arch32flags"
-                                       fi
-                               fi
-                       fi
-                       ;;
-               IRIX)
-                       if test -z "$OPTIM"; then
-                               if test "x$with_optim" = x; then
-                                       OPTIM="-O2"
-                               else
-                                       OPTIM="$with_optim $OPTIM"
-                               fi
-                       fi
-
-                       if test "x$with_optim" = x; then
-                               OPTIM="-fullwarn -woff 1183,1209,1349,1506,3201 $OPTIM"
-                       fi
-
-                       if test "x$enable_32bit" = xyes; then
-                               # Build 32-bit libraries, 64-bit base...
-                               if test -z "$with_arch32flags"; then
-                                       ARCH32FLAGS="-n32 -mips3"
-                               else
-                                       ARCH32FLAGS="$with_arch32flags"
-                               fi
-
-                               if test -z "$with_archflags"; then
-                                       if test -z "$with_arch64flags"; then
-                                               ARCHFLAGS="-64 -mips4"
-                                       else
-                                               ARCHFLAGS="$with_arch64flags"
-                                       fi
-                               fi
-                       fi
-
-                       if test "x$enable_64bit" = xyes; then
-                               # Build 64-bit libraries, 32-bit base...
-                               if test -z "$with_arch64flags"; then
-                                       ARCH64FLAGS="-64 -mips4"
-                               else
-                                       ARCH64FLAGS="$with_arch64flags"
-                               fi
-
-                               if test -z "$with_archflags"; then
-                                       if test -z "$with_arch32flags"; then
-                                               ARCHFLAGS="-n32 -mips3"
-                                       else
-                                               ARCHFLAGS="$with_arch32flags"
-                                       fi
-                               fi
-                       fi
-                       ;;
-               OSF*)
-                       # Tru64 UNIX aka Digital UNIX aka OSF/1
-                       if test -z "$OPTIM"; then
-                               if test "x$with_optim" = x; then
-                                       OPTIM="-O"
-                               else
-                                       OPTIM="$with_optim"
-                               fi
-                       fi
-                       ;;
-               SunOS*)
+       case $host_os_name in
+               sunos*)
                        # Solaris
                        if test -z "$OPTIM"; then
-                               if test "x$with_optim" = x; then
-                                       OPTIM="-xO2"
-                               else
-                                       OPTIM="$with_optim $OPTIM"
-                               fi
-                       fi
-
-                       if test $PICFLAG = 1; then
-                               OPTIM="-KPIC $OPTIM"
-                       fi
-
-                       if test "x$enable_32bit" = xyes; then
-                               # Compiling on a Solaris system, build 64-bit
-                               # binaries with separate 32-bit libraries...
-                               ARCH32FLAGS="-xarch=generic"
-
-                               if test "x$with_optim" = x; then
-                                       # Suppress all of Sun's questionable
-                                       # warning messages, and default to
-                                       # 64-bit compiles of everything else...
-                                       OPTIM="-w $OPTIM"
-                               fi
-
-                               if test -z "$with_archflags"; then
-                                       if test -z "$with_arch64flags"; then
-                                               ARCHFLAGS="-xarch=generic64"
-                                       else
-                                               ARCHFLAGS="$with_arch64flags"
-                                       fi
-                               fi
-                       else
-                               if test "x$enable_64bit" = xyes; then
-                                       # Build 64-bit libraries...
-                                       ARCH64FLAGS="-xarch=generic64"
-                               fi
-
-                               if test "x$with_optim" = x; then
-                                       # Suppress all of Sun's questionable
-                                       # warning messages, and default to
-                                       # 32-bit compiles of everything else...
-                                       OPTIM="-w $OPTIM"
-                               fi
-
-                               if test -z "$with_archflags"; then
-                                       if test -z "$with_arch32flags"; then
-                                               ARCHFLAGS="-xarch=generic"
-                                       else
-                                               ARCHFLAGS="$with_arch32flags"
-                                       fi
-                               fi
-                       fi
-                       ;;
-               UNIX_SVR*)
-                       # UnixWare
-                       if test -z "$OPTIM"; then
-                               if test "x$with_optim" = x; then
-                                       OPTIM="-O"
-                               else
-                                       OPTIM="$with_optim $OPTIM"
-                               fi
+                               OPTIM="-xO2"
                        fi
 
                        if test $PICFLAG = 1; then
@@ -481,40 +200,28 @@ else
                        fi
                        ;;
                *)
-                       # Running some other operating system; inform the user they
-                       # should contribute the necessary options to
-                       # cups-support@cups.org...
-                       echo "Building CUPS with default compiler optimizations; contact"
-                       echo "cups-bugs@cups.org with uname and compiler options needed"
-                       echo "for your platform, or set the CFLAGS and LDFLAGS environment"
-                       echo "variables before running configure."
+                       # Running some other operating system; inform the user
+                       # they should contribute the necessary options via
+                       # Github...
+                       echo "Building CUPS with default compiler optimizations; contact the CUPS developers on Github"
+                       echo "(https://github.com/apple/cups/issues) with the uname and compiler options needed for"
+                       echo "your platform, or set the CFLAGS and LDFLAGS environment variables before running"
+                       echo "configure."
                        ;;
        esac
 fi
 
 # Add general compiler options per platform...
-case $uname in
-       HP-UX*)
-               # HP-UX 10.20 (at least) needs this definition to get the
-               # h_errno global...
-               OPTIM="$OPTIM -D_XOPEN_SOURCE_EXTENDED"
-
-               # HP-UX 11.00 (at least) needs this definition to get the
-               # u_short type used by the IP headers...
-               OPTIM="$OPTIM -D_INCLUDE_HPUX_SOURCE"
-
-               # HP-UX 11.23 (at least) needs this definition to get the
-               # IPv6 header to work...
-               OPTIM="$OPTIM -D_HPUX_SOURCE"
-               ;;
-
-       OSF*)
-               # Tru64 UNIX aka Digital UNIX aka OSF/1 need to be told
-               # to be POSIX-compliant...
-               OPTIM="$OPTIM -D_XOPEN_SOURCE=500 -D_XOPEN_SOURCE_EXTENDED -D_OSF_SOURCE"
+case $host_os_name in
+       linux*)
+               # glibc 2.8 and higher breaks peer credentials unless you
+               # define _GNU_SOURCE...
+               OPTIM="$OPTIM -D_GNU_SOURCE"
+
+               # The -z relro option is provided by the Linux linker command to
+               # make relocatable data read-only.
+               if test x$enable_relro = xyes; then
+                       RELROFLAGS="-Wl,-z,relro,-z,now"
+               fi
                ;;
 esac
-
-dnl
-dnl End of "$Id: cups-compiler.m4 6975 2007-09-18 20:37:09Z mike $".
-dnl