build: initialize stack variables to zero by default

Newer versions of gcc and clang can include the ability to zero stack
variables by default.  Let's enable it so that we (a) reduce the risk of
writing stack contents to disk somewhere and (b) try to reduce
unpredictable program behavior based on random stack contents.  The
kernel added this 6 years ago, so I think it's mature enough for
fstests.

Signed-off-by: "Darrick J. Wong" <djwong@kernel.org>
Reviewed-by: Dave Chinner <dchinner@redhat.com>
Signed-off-by: Zorro Lang <zlang@kernel.org>

diff --git a/configure.ac b/configure.ac
index c81411e735a90d6a799ab531cf146d97697c4cf1..f3c8c643f0eb9e72183ed17b5eb9a63c33d8bbe7 100644 (file)
--- a/configure.ac
+++ b/configure.ac
@@ -72,6 +72,7 @@ AC_HAVE_NFTW
 AC_HAVE_RLIMIT_NOFILE
 AC_NEED_INTERNAL_XFS_IOC_EXCHANGE_RANGE
 AC_HAVE_FICLONE
+AC_HAVE_TRIVIAL_AUTO_VAR_INIT
 
 AC_CHECK_FUNCS([renameat2])
 AC_CHECK_FUNCS([reallocarray])

diff --git a/include/builddefs.in b/include/builddefs.in
index 7274cde8d0814c79483b3dcb63632603c9c72595..5b5864278682a43dedfa0a214b93fa068618fd0d 100644 (file)
--- a/include/builddefs.in
+++ b/include/builddefs.in
@@ -76,6 +76,7 @@ NEED_INTERNAL_XFS_IOC_EXCHANGE_RANGE = @need_internal_xfs_ioc_exchange_range@
 HAVE_FICLONE = @have_ficlone@
 
 GCCFLAGS = -funsigned-char -fno-strict-aliasing -Wall
+SANITIZER_CFLAGS += @autovar_init_cflags@
 
 ifeq ($(PKG_PLATFORM),linux)
 PCFLAGS = -D_GNU_SOURCE -D_FILE_OFFSET_BITS=64 $(GCCFLAGS)
@@ -90,7 +91,7 @@ GCFLAGS = $(OPTIMIZER) $(DEBUG) $(CPPFLAGS) \
        -I$(TOPDIR)/include -DVERSION=\"$(PKG_VERSION)\"
 
 # Global, Platform, Local CFLAGS
-CFLAGS += $(GCFLAGS) $(PCFLAGS) $(LCFLAGS)
+CFLAGS += $(GCFLAGS) $(PCFLAGS) $(LCFLAGS) $(SANITIZER_CFLAGS)
 
 include $(TOPDIR)/include/buildmacros
 

diff --git a/m4/package_libcdev.m4 b/m4/package_libcdev.m4
index a0d50f4d9b68e47e8acb6adedf6159fe177e6d9c..ed8fe6e32ae00aea9571fff13362754111ecca71 100644 (file)
--- a/m4/package_libcdev.m4
+++ b/m4/package_libcdev.m4
@@ -72,3 +72,17 @@ AC_DEFUN([AC_HAVE_FICLONE],
        AC_MSG_RESULT(yes)],[AC_MSG_RESULT(no)])
     AC_SUBST(have_ficlone)
   ])
+
+# Check if we have -ftrivial-auto-var-init=zero
+AC_DEFUN([AC_HAVE_TRIVIAL_AUTO_VAR_INIT],
+  [ AC_MSG_CHECKING([if C compiler supports zeroing automatic vars])
+    OLD_CFLAGS="$CFLAGS"
+    TEST_CFLAGS="-ftrivial-auto-var-init=zero"
+    CFLAGS="$CFLAGS $TEST_CFLAGS"
+    AC_LINK_IFELSE([AC_LANG_PROGRAM([])],
+        [AC_MSG_RESULT([yes])]
+        [autovar_init_cflags=$TEST_CFLAGS],
+        [AC_MSG_RESULT([no])])
+    CFLAGS="${OLD_CFLAGS}"
+    AC_SUBST(autovar_init_cflags)
+  ])