On 10/27/2017 09:44 PM, Nathan Sidwell wrote:
> On 10/27/2017 02:34 PM, Jakub Jelinek wrote:
> 
>> But when singly inheriting a polymorphic base and thus mapped to the same
>> vptr all but the last dtor will not be in charge, right?
> 
> Correct.
> 
>> So, if using build_clobber_this for this, instead of clobbering what we
>> clobber we'd just clear the single vptr (couldn't clobber the rest, even
>> if before the store, because that would make the earlier other vptr stores
>> dead).
> 
> ok (I'd not looked at the patch to see if in chargeness was signficant)
> 
> nathan
> 

Hello.

I'm sending v2 which only zeros vptr of object.

Ready to be installed after finishing tests?
Martin
>From 098932be5472656c834b402038accb0b861afcc1 Mon Sep 17 00:00:00 2001
From: marxin <mli...@suse.cz>
Date: Thu, 19 Oct 2017 11:10:19 +0200
Subject: [PATCH] Zero vptr in dtor for -fsanitize=vptr.

gcc/cp/ChangeLog:

2017-11-03  Martin Liska  <mli...@suse.cz>

	* decl.c (begin_destructor_body): In case of VPTR sanitization
	(with disabled recovery), zero vptr in order to catch virtual calls
	after lifetime of an object.

gcc/testsuite/ChangeLog:

2017-10-27  Martin Liska  <mli...@suse.cz>

	* g++.dg/ubsan/vptr-12.C: New test.
---
 gcc/cp/decl.c                        | 20 +++++++++++++++++++-
 gcc/testsuite/g++.dg/ubsan/vptr-12.C | 22 ++++++++++++++++++++++
 2 files changed, 41 insertions(+), 1 deletion(-)
 create mode 100644 gcc/testsuite/g++.dg/ubsan/vptr-12.C

diff --git a/gcc/cp/decl.c b/gcc/cp/decl.c
index d88c78f348b..d45cc29e636 100644
--- a/gcc/cp/decl.c
+++ b/gcc/cp/decl.c
@@ -15241,7 +15241,25 @@ begin_destructor_body (void)
       if (flag_lifetime_dse
 	  /* Clobbering an empty base is harmful if it overlays real data.  */
 	  && !is_empty_class (current_class_type))
-	finish_decl_cleanup (NULL_TREE, build_clobber_this ());
+      {
+	  if (sanitize_flags_p (SANITIZE_VPTR)
+	      && (flag_sanitize_recover & SANITIZE_VPTR) == 0)
+	    {
+	      tree binfo = TYPE_BINFO (current_class_type);
+	      tree ref
+		= cp_build_indirect_ref (current_class_ptr, RO_NULL,
+					 tf_warning_or_error);
+
+	      tree vtbl_ptr = build_vfield_ref (ref, TREE_TYPE (binfo));
+	      tree vtbl = build_zero_cst (TREE_TYPE (vtbl_ptr));
+	      tree stmt = cp_build_modify_expr (input_location, vtbl_ptr,
+						NOP_EXPR, vtbl,
+						tf_warning_or_error);
+	      finish_decl_cleanup (NULL_TREE, stmt);
+	    }
+	  else
+	    finish_decl_cleanup (NULL_TREE, build_clobber_this ());
+      }
 
       /* And insert cleanups for our bases and members so that they
 	 will be properly destroyed if we throw.  */
diff --git a/gcc/testsuite/g++.dg/ubsan/vptr-12.C b/gcc/testsuite/g++.dg/ubsan/vptr-12.C
new file mode 100644
index 00000000000..be5c074dfc1
--- /dev/null
+++ b/gcc/testsuite/g++.dg/ubsan/vptr-12.C
@@ -0,0 +1,22 @@
+// { dg-do run }
+// { dg-shouldfail "ubsan" }
+// { dg-options "-fsanitize=vptr -fno-sanitize-recover=vptr" }
+
+struct MyClass
+{
+  virtual ~MyClass () {}
+  virtual void Doit () {}
+};
+
+int
+main ()
+{
+  MyClass *c = new MyClass;
+  c->~MyClass ();
+  c->Doit ();
+
+  return 0;
+}
+
+// { dg-output "\[^\n\r]*vptr-12.C:16:\[0-9]*: runtime error: member call on address 0x\[0-9a-fA-F]* which does not point to an object of type 'MyClass'(\n|\r\n|\r)" }
+// { dg-output "0x\[0-9a-fA-F]*: note: object has invalid vptr(\n|\r\n|\r)" }
-- 
2.14.3

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