Hi!
Alex' 2 years old change to build_zero_init_1 to return NULL pointer with
reference type for references breaks the sanitizers, the assignment of NULL
to a reference typed member is then instrumented before it is overwritten
with a non-NULL address later on.
That change has been done to fix error recovery ICE during
process_init_constructor_record, where we:
if (TYPE_REF_P (fldtype))
{
if (complain & tf_error)
error ("member %qD is uninitialized reference", field);
else
return PICFLAG_ERRONEOUS;
}
a few lines earlier, but then continue and ICE when build_zero_init returns
NULL.
The following patch reverts the build_zero_init_1 change and instead creates
the NULL with reference type constants during the error recovery.
The pr84593.C testcase Alex' change was fixing still works as before.
Bootstrapped/regtested on x86_64-linux and i686-linux, ok for trunk?
2021-01-22 Jakub Jelinek <ja...@redhat.com>
PR sanitizer/95693
* init.c (build_zero_init_1): Revert the 2018-03-06 change to
return build_zero_cst for reference types.
* typeck2.c (process_init_constructor_record): Instead call
build_zero_cst here during error recovery instead of build_zero_init.
* g++.dg/ubsan/pr95693.C: New test.
--- gcc/cp/init.c.jj 2021-01-04 10:25:48.384125675 +0100
+++ gcc/cp/init.c 2021-01-21 13:59:26.863840340 +0100
@@ -288,10 +288,7 @@ build_zero_init_1 (tree type, tree nelts
else if (VECTOR_TYPE_P (type))
init = build_zero_cst (type);
else
- {
- gcc_assert (TYPE_REF_P (type));
- init = build_zero_cst (type);
- }
+ gcc_assert (TYPE_REF_P (type));
/* In all cases, the initializer is a constant. */
if (init)
--- gcc/cp/typeck2.c.jj 2021-01-21 14:22:45.000000000 +0100
+++ gcc/cp/typeck2.c 2021-01-21 14:24:25.119772897 +0100
@@ -1609,10 +1609,14 @@ process_init_constructor_record (tree type, tree init,
int nested, int flags,
warning (OPT_Wmissing_field_initializers,
"missing initializer for member %qD", field);
- if (!zero_init_p (fldtype)
- || skipped < 0)
- next = build_zero_init (fldtype, /*nelts=*/NULL_TREE,
- /*static_storage_p=*/false);
+ if (!zero_init_p (fldtype) || skipped < 0)
+ {
+ if (TYPE_REF_P (fldtype))
+ next = build_zero_cst (fldtype);
+ else
+ next = build_zero_init (fldtype, /*nelts=*/NULL_TREE,
+ /*static_storage_p=*/false);
+ }
else
{
/* The default zero-initialization is fine for us; don't
--- gcc/testsuite/g++.dg/ubsan/pr95693.C.jj 2021-01-21 14:31:31.536921423
+0100
+++ gcc/testsuite/g++.dg/ubsan/pr95693.C 2021-01-21 14:32:42.590114353
+0100
@@ -0,0 +1,26 @@
+// PR sanitizer/95693
+// { dg-do run }
+// { dg-options "-O2 -fsanitize=undefined -fno-sanitize-recover=undefined" }
+
+int g = 9;
+
+struct A {
+ A () : a(g) {}
+private:
+ int &a;
+};
+
+struct B {
+ A payload;
+};
+
+struct C : public B {
+ C () : B () {}
+ A p;
+};
+
+int
+main ()
+{
+ C t;
+}
Jakub
