On 9/6/24 2:38 PM, Jakub Jelinek wrote:
On Wed, Sep 04, 2024 at 10:31:48PM +0200, Franz Sirl wrote:
Hmm, it just occured to me, how about adding !NONVIRTUAL here? When
NONVIRTUAL is true, there is no conditional stmt at all, or?
Yeah, that makes sense, the problem doesn't happen in that case.
Here is an adjusted patch, bootstrapped/regtested on x86_64-linux
and i686-linux, ok for trunk?
OK.
2024-09-06 Jakub Jelinek <ja...@redhat.com>
PR c++/116449
* typeck.cc (get_member_function_from_ptrfunc): Use save_expr
on instance_ptr and function even if it doesn't have side-effects,
as long as it isn't a decl.
* g++.dg/ubsan/pr116449.C: New test.
--- gcc/cp/typeck.cc.jj 2024-09-02 17:07:30.115098114 +0200
+++ gcc/cp/typeck.cc 2024-09-04 19:08:24.127490242 +0200
@@ -4188,10 +4188,23 @@ get_member_function_from_ptrfunc (tree *
if (!nonvirtual && is_dummy_object (instance_ptr))
nonvirtual = true;
- if (TREE_SIDE_EFFECTS (instance_ptr))
- instance_ptr = instance_save_expr = save_expr (instance_ptr);
+ /* Use save_expr even when instance_ptr doesn't have side-effects,
+ unless it is a simple decl (save_expr won't do anything on
+ constants), so that we don't ubsan instrument the expression
+ multiple times. See PR116449. */
+ if (TREE_SIDE_EFFECTS (instance_ptr)
+ || (!nonvirtual && !DECL_P (instance_ptr)))
+ {
+ instance_save_expr = save_expr (instance_ptr);
+ if (instance_save_expr == instance_ptr)
+ instance_save_expr = NULL_TREE;
+ else
+ instance_ptr = instance_save_expr;
+ }
- if (TREE_SIDE_EFFECTS (function))
+ /* See above comment. */
+ if (TREE_SIDE_EFFECTS (function)
+ || (!nonvirtual && !DECL_P (function)))
function = save_expr (function);
/* Start by extracting all the information from the PMF itself. */
--- gcc/testsuite/g++.dg/ubsan/pr116449.C.jj 2024-09-04 18:58:46.106764285
+0200
+++ gcc/testsuite/g++.dg/ubsan/pr116449.C 2024-09-04 18:58:46.106764285
+0200
@@ -0,0 +1,14 @@
+// PR c++/116449
+// { dg-do compile }
+// { dg-options "-O2 -Wall -fsanitize=undefined" }
+
+struct C { void foo (int); void bar (); int c[16]; };
+typedef void (C::*P) ();
+struct D { P d; };
+static D e[1] = { { &C::bar } };
+
+void
+C::foo (int x)
+{
+ (this->*e[c[x]].d) ();
+}
Jakub
