On Tue, Nov 19, 2013 at 10:07:00AM -0500, Jason Merrill wrote:
> On 11/18/2013 11:39 AM, Marek Polacek wrote:
> >+ init = fold_build2 (COMPOUND_EXPR, TREE_TYPE (init),
> >+ ubsan_instrument_reference (input_location, init),
> >+ init);
>
> This looks like it will evaluate init twice.
You're right. I wanted to use cp_save_expr and/or stabilize_expr, but
that didn't work out. So I resorted to restrict the condition a bit
and only pass INDIRECT_REFs to the ubsan routine (which, after all,
has
if (!INDIRECT_REF_P (init))
return init;
And in that case, it seems we don't have to worry about multiple evaluation
of the initializer.
Nevertheless, I added a test that checks that we don't evaluate the
initializer twice.
BTW, we still detect e.g.
int *p = 0;
int &qr = ++*p;
while clang doesn't detect it at all.
So, ok for trunk? Ubsan testsuite passes.
2013-12-03 Marek Polacek <pola...@redhat.com>
* c-family/c-ubsan.h (extern tree ubsan_instrument_division):
* c-family/c-ubsan.c (ubsan_instrument_return):
(ubsan_instrument_reference):
* cp/decl.c (cp_finish_decl):
* testsuite/g++.dg/ubsan/null-1.C (main):
--- gcc/c-family/c-ubsan.h.mp2 2013-12-03 19:07:28.382466550 +0100
+++ gcc/c-family/c-ubsan.h 2013-12-03 19:09:02.245819384 +0100
@@ -25,5 +25,6 @@ extern tree ubsan_instrument_division (l
extern tree ubsan_instrument_shift (location_t, enum tree_code, tree, tree);
extern tree ubsan_instrument_vla (location_t, tree);
extern tree ubsan_instrument_return (location_t);
+extern tree ubsan_instrument_reference (location_t, tree);
#endif /* GCC_C_UBSAN_H */
--- gcc/c-family/c-ubsan.c.mp2 2013-12-03 19:07:33.437485687 +0100
+++ gcc/c-family/c-ubsan.c 2013-12-03 19:08:15.649643663 +0100
@@ -190,3 +190,30 @@ ubsan_instrument_return (location_t loc)
tree t = builtin_decl_explicit (BUILT_IN_UBSAN_HANDLE_MISSING_RETURN);
return build_call_expr_loc (loc, t, 1, build_fold_addr_expr_loc (loc, data));
}
+
+/* Instrument reference binding, that is, ensure that the reference
+ declaration doesn't bind the reference to a NULL pointer. */
+
+tree
+ubsan_instrument_reference (location_t loc, tree init)
+{
+ if (!INDIRECT_REF_P (init))
+ /* This may happen, e.g. int &&r4 = p;, so don't put an assert here. */
+ return init;
+
+ init = TREE_OPERAND (init, 0);
+ tree eq_expr = fold_build2 (EQ_EXPR, boolean_type_node, init,
+ build_zero_cst (TREE_TYPE (init)));
+ const struct ubsan_mismatch_data m
+ = { build_zero_cst (pointer_sized_int_node),
+ build_int_cst (unsigned_char_type_node, UBSAN_REF_BINDING)};
+ tree data = ubsan_create_data ("__ubsan_null_data",
+ loc, &m,
+ ubsan_type_descriptor (TREE_TYPE (init),
+ true), NULL_TREE);
+ data = build_fold_addr_expr_loc (loc, data);
+ tree fn = builtin_decl_implicit (BUILT_IN_UBSAN_HANDLE_TYPE_MISMATCH);
+ fn = build_call_expr_loc (loc, fn, 2, data,
+ build_zero_cst (pointer_sized_int_node));
+ return fold_build3 (COND_EXPR, void_type_node, eq_expr, fn, void_zero_node);
+}
--- gcc/cp/decl.c.mp2 2013-12-03 19:07:38.678505371 +0100
+++ gcc/cp/decl.c 2013-12-03 20:40:34.649989640 +0100
@@ -6245,6 +6245,12 @@ cp_finish_decl (tree decl, tree init, bo
if (decl_maybe_constant_var_p (decl))
TREE_CONSTANT (decl) = 1;
}
+ if (flag_sanitize & SANITIZE_NULL
+ && TREE_CODE (type) == REFERENCE_TYPE
+ && INDIRECT_REF_P (init))
+ init = fold_build2 (COMPOUND_EXPR, TREE_TYPE (init),
+ ubsan_instrument_reference (input_location, init),
+ init);
}
if (processing_template_decl)
--- gcc/testsuite/g++.dg/ubsan/null-1.C.mp2 2013-11-22 16:16:05.073181508
+0100
+++ gcc/testsuite/g++.dg/ubsan/null-1.C 2013-12-03 19:23:48.351305205 +0100
@@ -0,0 +1,32 @@
+// { dg-do run }
+// { dg-options "-fsanitize=null -Wall -Wno-unused-variable -std=c++11" }
+// { dg-skip-if "" { *-*-* } { "-flto" } { "" } }
+
+typedef const long int L;
+
+int
+main (void)
+{
+ int *p = 0;
+ L *l = 0;
+
+ int &r = *p;
+ auto &r2 = *p;
+ L &lr = *l;
+
+ /* Try an rvalue reference. */
+ auto &&r3 = *p;
+
+ /* Don't evaluate the reference initializer twice. */
+ int i = 1;
+ int *q = &i;
+ int &qr = ++*q;
+ if (i != 2)
+ __builtin_abort ();
+ return 0;
+}
+
+// { dg-output "reference binding to null pointer of type 'int'(\n|\r\n|\r)" }
+// { dg-output "\[^\n\r]*reference binding to null pointer of type
'int'(\n|\r\n|\r)" }
+// { dg-output "\[^\n\r]*reference binding to null pointer of type 'const
L'(\n|\r\n|\r)" }
+// { dg-output "\[^\n\r]*reference binding to null pointer of type
'int'(\n|\r\n|\r)" }
Marek
