build system: enable gcc's stack protection

Implements #1370.

Rakefile

@@ -108,6 +108,7 @@ def setup_globals
   cflags_common           += " #{c(:WNO_INCONSISTENT_MISSING_OVERRIDE)} #{c(:WNO_POTENTIALLY_EVALUATED_EXPRESSION)}"
   cflags_common           += " #{c(:OPTIMIZATION_CFLAGS)} -D_FILE_OFFSET_BITS=64"
   cflags_common           += " -DMTX_LOCALE_DIR=\\\"#{c(:localedir)}\\\" -DMTX_PKG_DATA_DIR=\\\"#{c(:pkgdatadir)}\\\" -DMTX_DOC_DIR=\\\"#{c(:docdir)}\\\""
+  cflags_common           += " #{c(:FSTACK_PROTECTOR)}"
   cflags_common           += " -Ilib/libebml -Ilib/libmatroska"                          if c?(:EBML_MATROSKA_INTERNAL)
   cflags_common           += " #{c(:MATROSKA_CFLAGS)} #{c(:EBML_CFLAGS)} #{c(:EXTRA_CFLAGS)} #{c(:DEBUG_CFLAGS)} #{c(:PROFILING_CFLAGS)} #{c(:USER_CPPFLAGS)}"
   cflags_common           += " -mno-ms-bitfields -DWINVER=0x0500 -D_WIN32_WINNT=0x0500 " if c?(:MINGW)

ac/compiler_flags.m4

@@ -7,6 +7,7 @@ if test x"$ac_cv_compiler_is_clang" = xyes; then
   QUNUSED_ARGUMENTS="-Qunused-arguments"
   WNO_SELF_ASSIGN="-Wno-self-assign"
   WNO_MISMATCHED_TAGS="-Wno-mismatched-tags"
+  FSTACK_PROTECTOR=""
 
   ac_save_CXXFLAGS="$CXXFLAGS"
   AC_LANG_PUSH(C++)
@@ -22,12 +23,17 @@ if test x"$ac_cv_compiler_is_clang" = xyes; then
 
 else
   WNO_MAYBE_UNINITIALIZED="-Wno-maybe-uninitialized"
+  FSTACK_PROTECTOR="-fstack-protector"
 
-  if check_version 4.8.0 $ac_cv_gcc_version ; then
+  if check_version 4.9.0 $ac_cv_gcc_version ; then
+    FSTACK_PROTECTOR="-fstack-protector-strong"
+
+  elif check_version 4.8.0 $ac_cv_gcc_version ; then
     WLOGICAL_OP="-Wlogical-op"
   fi
 fi
 
+AC_SUBST(FSTACK_PROTECTOR)
 AC_SUBST(QUNUSED_ARGUMENTS)
 AC_SUBST(WNO_SELF_ASSIGN)
 AC_SUBST(WNO_MISMATCHED_TAGS)

build-config.in

@@ -85,6 +85,7 @@ EBML_MATROSKA_INTERNAL = @EBML_MATROSKA_INTERNAL@
 EGREP = @EGREP@
 EXTRA_CFLAGS = @EXTRA_CFLAGS@
 EXTRA_LDFLAGS = @EXTRA_LDFLAGS@
+FSTACK_PROTECTOR = @FSTACK_PROTECTOR@
 GTEST_TYPE = @GTEST_TYPE@
 LDFLAGS_RPATHS = @LDFLAGS_RPATHS@
 FLAC_LIBS = @FLAC_LIBS@