Now that we are -fsanitize=undefined clean make sure we keep it that way.

We do have to disable alignment checking. Because we might explicitly
use unaligned accesses (see ALLOW_UNALIGNED). And we have to disable
integer overflow checking when running the tests under valgrind. Because
those are unreliable under VEX emulation.

Rename DISTCHECK_CONFIGURE_FLAGS to AM_DISTCHECK_CONFIGURE_FLAGS, so the
user can override. And add --enable-sanitize-undefined.

Signed-off-by: Mark Wielaard <mjw@redhat.com>
---
 ChangeLog    |  8 ++++++++
 Makefile.am  |  4 ++--
 configure.ac | 23 +++++++++++++++++++++++
 3 files changed, 33 insertions(+), 2 deletions(-)

diff --git a/ChangeLog b/ChangeLog
index d3e46fc..91b2259 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,11 @@
+2015-05-21  Mark Wielaard  <mjw@redhat.com>
+
+	* configure.ac: Add --enable-sanitize-undefined.
+	Add -fno-sanitize=signed-integer-overflow when both
+	--enable-sanitize-undefined and --enable-valgrind are given.
+	* Makefile.am (DISTCHECK_CONFIGURE_FLAGS): Rename to...
+	(AM_DISTCHECK_CONFIGURE_FLAGS): this. Add --enable-sanitize-undefined.
+
 2015-05-04  Anthony G. Basile  <blueness@gentoo.org>
 
 	* configure.ac (argp_LDADD): Check if libc has argp and set
diff --git a/Makefile.am b/Makefile.am
index d044a7c..1454d04 100644
--- a/Makefile.am
+++ b/Makefile.am
@@ -33,9 +33,9 @@ EXTRA_DIST = elfutils.spec GPG-KEY NOTES CONTRIBUTING \
 # Make sure the test build uses the same compiler, which on e.g. ppc64
 # determines which platform we are actually testing.
 # Run all tests under valgrind.
-DISTCHECK_CONFIGURE_FLAGS = \
+AM_DISTCHECK_CONFIGURE_FLAGS = \
 	--libdir=`echo $(libdir) | sed "s,^$(exec_prefix),$$dc_install_base,"`\
-	--enable-valgrind \
+	--enable-valgrind --enable-sanitize-undefined \
 	CC="$(CC)"
 
 distcheck-hook:
diff --git a/configure.ac b/configure.ac
index 68b7f5b..7415233 100644
--- a/configure.ac
+++ b/configure.ac
@@ -193,10 +193,32 @@ if test "$use_gcov" = yes; then
 fi
 AM_CONDITIONAL(GCOV, test "$use_gcov" = yes)
 
+AC_ARG_ENABLE([sanitize-undefined],
+              AS_HELP_STRING([--enable-sanitize-undefined],
+                             [Use gcc undefined behaviour sanitizer]),
+                             [use_undefined=$enableval], [use_undefined=no])
+if test "$use_undefined" = yes; then
+  old_CFLAGS="$CFLAGS"
+  old_CXXFLAGS="$CXXFLAGS"
+  # We explicitly use unaligned access when possible (see ALLOW_UNALIGNED)
+  # We want to fail immediately on first error, don't try to recover.
+  CFLAGS="$CFLAGS -fsanitize=undefined -fno-sanitize=alignment -fno-sanitize-recover"
+  CXXFLAGS="$CXXFLAGS -fsanitize=undefined -fno-sanitize=alignment -fno-sanitize-recover"
+  AC_COMPILE_IFELSE([AC_LANG_SOURCE([])], use_undefined=yes, use_undefined=no)
+  AS_IF([test "x$use_undefined" != xyes],
+        AC_MSG_WARN([gcc undefined behaviour sanitizer not available])
+        CFLAGS="$old_CFLAGS" CXXFLAGS="$old_CXXFLAGS")
+fi
+
 AC_ARG_ENABLE([valgrind],
 AS_HELP_STRING([--enable-valgrind],[run all tests under valgrind]),
 [use_valgrind=$enableval], [use_valgrind=no])
 if test "$use_valgrind" = yes; then
+  # signed overflow checking isn't reliable under valgrind
+  if test "$use_undefined" = yes; then
+    CFLAGS="$CFLAGS -fno-sanitize=signed-integer-overflow"
+    CXXFLAGS="$CXXFLAGS -fno-sanitize=signed-integer-overflow"
+  fi
   AC_CHECK_PROG(HAVE_VALGRIND, valgrind, yes, no)
   if test "$HAVE_VALGRIND" = "no"; then
     AC_MSG_ERROR([valgrind not found])
@@ -421,6 +443,7 @@ AC_MSG_NOTICE([
     gprof support                      : ${use_gprof}
     gcov support                       : ${use_gcov}
     run all tests under valgrind       : ${use_valgrind}
+    gcc undefined behaviour sanitizer  : ${use_undefined}
     use rpath in tests                 : ${tests_use_rpath}
     test biarch                        : ${utrace_cv_cc_biarch}
 ])
-- 
2.1.0