Hi!
The SAVE_EXPR was needed here only in the previous implementation where
we emitted more code inline early, now that we have UBSAN_VPTR internal call
that is lowered during sanopt, we use it just once.
Furthermore, the SAVE_EXPR caused e.g. the following two testcases to
misbehave, as a shared CALL_EXPR tree of a destructor call containing
the UBSA_VPTR with SAVE_EXPR was gimplified in two places - in one finally
and another cleanup. As the finally wasn't dominating the cleanup
(obviously we don't want to destruct twice), the SAVE_EXPR was initialized
in one place and we had uninitialized var in the other spot.
Fixed by not wrapping the vptr load into a SAVE_EXPR.
Bootstrapped/regtested on x86_64-linux and i686-linux, committed to trunk.
2015-01-29 Jakub Jelinek <ja...@redhat.com>
PR c++/64717
* cp-ubsan.c (cp_ubsan_instrument_vptr): Don't wrap vptr
into SAVE_EXPR.
* g++.dg/ubsan/pr64717-1.C: New test.
* g++.dg/ubsan/pr64717-2.C: New test.
--- gcc/cp/cp-ubsan.c.jj 2015-01-15 23:57:07.000000000 +0100
+++ gcc/cp/cp-ubsan.c 2015-01-29 17:57:11.134236397 +0100
@@ -107,7 +107,6 @@ cp_ubsan_instrument_vptr (location_t loc
fold_build2 (NE_EXPR, boolean_type_node, op,
build_zero_cst (TREE_TYPE (op))),
vptr, build_int_cst (uint64_type_node, 0));
- vptr = build1_loc (loc, SAVE_EXPR, uint64_type_node, vptr);
tree ti_decl = get_tinfo_decl (type);
mark_used (ti_decl);
tree ptype = build_pointer_type (type);
--- gcc/testsuite/g++.dg/ubsan/pr64717-1.C.jj 2015-01-29 18:03:14.428052606
+0100
+++ gcc/testsuite/g++.dg/ubsan/pr64717-1.C 2015-01-29 18:02:39.000000000
+0100
@@ -0,0 +1,15 @@
+// PR c++/64717
+// { dg-do compile }
+// { dg-options "-O2 -Wuninitialized -fsanitize=vptr" }
+
+class Foo {};
+Foo make_foo ();
+
+struct Handle { virtual ~Handle (); };
+Handle open (Foo);
+
+void
+bar ()
+{
+ Handle file (open (make_foo ())); // { dg-bogus "is used uninitialized" }
+}
--- gcc/testsuite/g++.dg/ubsan/pr64717-2.C.jj 2015-01-29 18:03:17.488000521
+0100
+++ gcc/testsuite/g++.dg/ubsan/pr64717-2.C 2015-01-29 18:02:32.000000000
+0100
@@ -0,0 +1,20 @@
+// PR c++/64717
+// { dg-do compile }
+// { dg-options "-O2 -Wuninitialized -fsanitize=vptr" }
+
+class ios {};
+
+struct stringstream : virtual ios {
+ stringstream (char *);
+ ~stringstream ();
+};
+
+struct string { char *c_str (); };
+
+string make_str ();
+
+void
+bar ()
+{
+ stringstream param (make_str ().c_str ()); // { dg-bogus "is used
uninitialized" }
+}
Jakub
