configure: Use -fstack-protector-strong when available

Testing whether the compiler supports it is a bit tricky.

The obvious AX_APPEND_COMPILE_FLAGS([-fstack-protector-strong])
doesn't suffice, since some ports of the GNU toolchain reportedly pass
this test, then fail to link.  That's because the compiler accepts the
flag, duly emits references to helper code in libc, but libc doesn't
provide, and linking fails.

Instead, use AX_APPEND_LINK_FLAGS with an input source that makes the
compiler emit the extra stack checking code.  This requires the latest
version from the autoconf-archive, so update m4/ax* to commit e3d948b.
Also update m4/my_append_compile_flags.m4 to keep it in sync with
upstream's ax_append_compile_flags.m4.

Signed-off-by: Markus Armbruster <armbru@pond.sub.org>

diff --git a/configure.ac b/configure.ac
index f5dd1b5855c5bcb644ca20486f62b3e05a7ec0de..36d358ec230671a59991aa0b8ad9eab8341cb241 100644 (file)
--- a/configure.ac
+++ b/configure.ac
@@ -140,6 +140,23 @@ MY_APPEND_COMPILE_FLAGS([dnl
 -fno-strict-aliasing dnl
 -fno-strict-overflow])
 
 -fno-strict-aliasing dnl
 -fno-strict-overflow])
 

+# Emit extra code to check for buffer overflows
+# Could fall back to -fstack-protector when -fstack-protector-strong
+# isnt't supported, for users of older compilers.  Doesn't seem worth
+# the trouble, though.
+# Some ports of the GNU toolchain reportedly support it in the
+# compiler, but not libc.  Use a test program that makes the compiler
+# emit the extra stack checking code, and test it compiles and links.
+AX_APPEND_LINK_FLAGS([-fstack-protector-strong], [], [],
+    [AC_LANG_SOURCE([[
+int
+main(int argc, char *argv[])
+{
+    char arr[64], *dst = arr, *src = argv[0];
+    while ((*dst++ = *src++)) ;
+}
+    ]])])
+

 
 ### Checks for library functions
 
 
 ### Checks for library functions
 

diff --git a/m4/ax_append_flag.m4 b/m4/ax_append_flag.m4
index aeab89979ac1ae08522681ed58decb11987273a6..08f2e07ec61bd428279958705ab200cded8e59d0 100644 (file)
--- a/m4/ax_append_flag.m4
+++ b/m4/ax_append_flag.m4
@@ -49,7 +49,7 @@
 #   modified version of the Autoconf Macro, you may extend this special
 #   exception to the GPL to apply to your modified version as well.
 
 #   modified version of the Autoconf Macro, you may extend this special
 #   exception to the GPL to apply to your modified version as well.
 

-#serial 5
+#serial 6

 
 AC_DEFUN([AX_APPEND_FLAG],
 [dnl
 
 AC_DEFUN([AX_APPEND_FLAG],
 [dnl


@@ -59,7 +59,7 @@ AS_VAR_SET_IF(FLAGS,[
   AS_CASE([" AS_VAR_GET(FLAGS) "],
     [*" $1 "*], [AC_RUN_LOG([: FLAGS already contains $1])],
     [
   AS_CASE([" AS_VAR_GET(FLAGS) "],
     [*" $1 "*], [AC_RUN_LOG([: FLAGS already contains $1])],
     [

-     AS_VAR_APPEND(FLAGS," $1")
+     AS_VAR_APPEND(FLAGS,[" $1"])

      AC_RUN_LOG([: FLAGS="$FLAGS"])
     ])
   ],
      AC_RUN_LOG([: FLAGS="$FLAGS"])
     ])
   ],

diff --git a/m4/ax_append_link_flags.m4 b/m4/ax_append_link_flags.m4
new file mode 100644 (file)
index 0000000..fd70fc7
--- /dev/null
+++ b/m4/ax_append_link_flags.m4
@@ -0,0 +1,65 @@
+# ===========================================================================
+#   http://www.gnu.org/software/autoconf-archive/ax_append_link_flags.html
+# ===========================================================================
+#
+# SYNOPSIS
+#
+#   AX_APPEND_LINK_FLAGS([FLAG1 FLAG2 ...], [FLAGS-VARIABLE], [EXTRA-FLAGS], [INPUT])
+#
+# DESCRIPTION
+#
+#   For every FLAG1, FLAG2 it is checked whether the linker works with the
+#   flag.  If it does, the flag is added FLAGS-VARIABLE
+#
+#   If FLAGS-VARIABLE is not specified, the linker's flags (LDFLAGS) is
+#   used. During the check the flag is always added to the linker's flags.
+#
+#   If EXTRA-FLAGS is defined, it is added to the linker's default flags
+#   when the check is done.  The check is thus made with the flags: "LDFLAGS
+#   EXTRA-FLAGS FLAG".  This can for example be used to force the linker to
+#   issue an error when a bad flag is given.
+#
+#   INPUT gives an alternative input source to AC_COMPILE_IFELSE.
+#
+#   NOTE: This macro depends on the AX_APPEND_FLAG and AX_CHECK_LINK_FLAG.
+#   Please keep this macro in sync with AX_APPEND_COMPILE_FLAGS.
+#
+# LICENSE
+#
+#   Copyright (c) 2011 Maarten Bosmans <mkbosmans@gmail.com>
+#
+#   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, either version 3 of the License, or (at your
+#   option) any later version.
+#
+#   This program is distributed in the hope that it will be useful, but
+#   WITHOUT ANY WARRANTY; without even the implied warranty of
+#   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General
+#   Public License for more details.
+#
+#   You should have received a copy of the GNU General Public License along
+#   with this program. If not, see <http://www.gnu.org/licenses/>.
+#
+#   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, even though portions of the text of the
+#   Macro appear in them. The GNU General Public License (GPL) does govern
+#   all other use of the material that constitutes the Autoconf Macro.
+#
+#   This special exception to the GPL applies to versions of the Autoconf
+#   Macro released by the Autoconf Archive. When you make and distribute a
+#   modified version of the Autoconf Macro, you may extend this special
+#   exception to the GPL to apply to your modified version as well.
+
+#serial 5
+
+AC_DEFUN([AX_APPEND_LINK_FLAGS],
+[AX_REQUIRE_DEFINED([AX_CHECK_LINK_FLAG])
+AX_REQUIRE_DEFINED([AX_APPEND_FLAG])
+for flag in $1; do
+  AX_CHECK_LINK_FLAG([$flag], [AX_APPEND_FLAG([$flag], [m4_default([$2], [LDFLAGS])])], [], [$3], [$4])
+done
+])dnl AX_APPEND_LINK_FLAGS

diff --git a/m4/ax_check_link_flag.m4 b/m4/ax_check_link_flag.m4
new file mode 100644 (file)
index 0000000..eb01a6c
--- /dev/null
+++ b/m4/ax_check_link_flag.m4
@@ -0,0 +1,74 @@
+# ===========================================================================
+#    http://www.gnu.org/software/autoconf-archive/ax_check_link_flag.html
+# ===========================================================================
+#
+# SYNOPSIS
+#
+#   AX_CHECK_LINK_FLAG(FLAG, [ACTION-SUCCESS], [ACTION-FAILURE], [EXTRA-FLAGS], [INPUT])
+#
+# DESCRIPTION
+#
+#   Check whether the given FLAG works with the linker or gives an error.
+#   (Warnings, however, are ignored)
+#
+#   ACTION-SUCCESS/ACTION-FAILURE are shell commands to execute on
+#   success/failure.
+#
+#   If EXTRA-FLAGS is defined, it is added to the linker's default flags
+#   when the check is done.  The check is thus made with the flags: "LDFLAGS
+#   EXTRA-FLAGS FLAG".  This can for example be used to force the linker to
+#   issue an error when a bad flag is given.
+#
+#   INPUT gives an alternative input source to AC_LINK_IFELSE.
+#
+#   NOTE: Implementation based on AX_CFLAGS_GCC_OPTION. Please keep this
+#   macro in sync with AX_CHECK_{PREPROC,COMPILE}_FLAG.
+#
+# LICENSE
+#
+#   Copyright (c) 2008 Guido U. Draheim <guidod@gmx.de>
+#   Copyright (c) 2011 Maarten Bosmans <mkbosmans@gmail.com>
+#
+#   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, either version 3 of the License, or (at your
+#   option) any later version.
+#
+#   This program is distributed in the hope that it will be useful, but
+#   WITHOUT ANY WARRANTY; without even the implied warranty of
+#   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General
+#   Public License for more details.
+#
+#   You should have received a copy of the GNU General Public License along
+#   with this program. If not, see <http://www.gnu.org/licenses/>.
+#
+#   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, even though portions of the text of the
+#   Macro appear in them. The GNU General Public License (GPL) does govern
+#   all other use of the material that constitutes the Autoconf Macro.
+#
+#   This special exception to the GPL applies to versions of the Autoconf
+#   Macro released by the Autoconf Archive. When you make and distribute a
+#   modified version of the Autoconf Macro, you may extend this special
+#   exception to the GPL to apply to your modified version as well.
+
+#serial 4
+
+AC_DEFUN([AX_CHECK_LINK_FLAG],
+[AC_PREREQ(2.64)dnl for _AC_LANG_PREFIX and AS_VAR_IF
+AS_VAR_PUSHDEF([CACHEVAR],[ax_cv_check_ldflags_$4_$1])dnl
+AC_CACHE_CHECK([whether the linker accepts $1], CACHEVAR, [
+  ax_check_save_flags=$LDFLAGS
+  LDFLAGS="$LDFLAGS $4 $1"
+  AC_LINK_IFELSE([m4_default([$5],[AC_LANG_PROGRAM()])],
+    [AS_VAR_SET(CACHEVAR,[yes])],
+    [AS_VAR_SET(CACHEVAR,[no])])
+  LDFLAGS=$ax_check_save_flags])
+AS_VAR_IF(CACHEVAR,yes,
+  [m4_default([$2], :)],
+  [m4_default([$3], :)])
+AS_VAR_POPDEF([CACHEVAR])dnl
+])dnl AX_CHECK_LINK_FLAGS

diff --git a/m4/my_append_compile_flags.m4 b/m4/my_append_compile_flags.m4
index d96fab1d0fb6b9abe4f4cc7ed4923fa5d8bd8745..aa4bf409cd9a2496a2c656d727601a7c12059edd 100644 (file)
--- a/m4/my_append_compile_flags.m4
+++ b/m4/my_append_compile_flags.m4
@@ -1,6 +1,6 @@
 # SYNOPSIS
 #
 # SYNOPSIS
 #

-#   MY_APPEND_COMPILE_FLAGS([FLAG1 FLAG2 ...], [FLAGS-VARIABLE], [EXTRA-FLAGS])
+#   MY_APPEND_COMPILE_FLAGS([FLAG1 FLAG2 ...], [FLAGS-VARIABLE], [EXTRA-FLAGS], [INPUT])

 #
 # DESCRIPTION
 #
 #
 # DESCRIPTION
 #


@@ -20,6 +20,8 @@
 #   the flags: "CFLAGS EXTRA-FLAGS FLAG".  This can for example be used to
 #   force the compiler to issue an error when a bad flag is given.
 #
 #   the flags: "CFLAGS EXTRA-FLAGS FLAG".  This can for example be used to
 #   force the compiler to issue an error when a bad flag is given.
 #

+#   INPUT gives an alternative input source to AC_COMPILE_IFELSE.
+#

 #   NOTE: This macro depends on the AX_APPEND_FLAG and
 #   AX_CHECK_COMPILE_FLAG. Please keep this macro in sync with
 #   MY_APPEND_LINK_FLAGS.
 #   NOTE: This macro depends on the AX_APPEND_FLAG and
 #   AX_CHECK_COMPILE_FLAG. Please keep this macro in sync with
 #   MY_APPEND_LINK_FLAGS.


@@ -62,6 +64,6 @@ AC_DEFUN([MY_APPEND_COMPILE_FLAGS],
 AX_REQUIRE_DEFINED([AX_APPEND_FLAG])
 for flag in $1; do
   tflag=`echo "$flag" | sed 's/^-Wno-/-W/'`
 AX_REQUIRE_DEFINED([AX_APPEND_FLAG])
 for flag in $1; do
   tflag=`echo "$flag" | sed 's/^-Wno-/-W/'`

-  AX_CHECK_COMPILE_FLAG([$tflag], [AX_APPEND_FLAG([$flag], [$2])], [], [$3])
+  AX_CHECK_COMPILE_FLAG([$tflag], [AX_APPEND_FLAG([$flag], [$2])], [], [$3], [$4])

 done
 ])dnl MY_APPEND_COMPILE_FLAGS
 done
 ])dnl MY_APPEND_COMPILE_FLAGS