On Wed, Sep 09, 2015 at 06:18:25PM +0200, Markus Trippelsdorf wrote:
> Tested on ppc64le.
> OK for trunk and gcc-5?
>
> PR sanitizer/67258
> * ubsan/ubsan_type_hash.cc: Cherry pick upstream r244101.
Please add
-fno-sanitize-recover=vptr
to dg-options.
Ok with that change.
> --- /dev/null
> +++ b/gcc/testsuite/g++.dg/ubsan/vptr-10.C
> @@ -0,0 +1,15 @@
> +// { dg-do run }
> +// { dg-options "-fsanitize=vptr" }
> +
> +struct A
> +{
> + virtual ~A() {}
> +};
> +struct B : virtual A {};
> +struct C : virtual A {};
> +struct D : B, virtual C {};
> +
> +int main()
> +{
> + D d;
> +}
> diff --git a/libsanitizer/ubsan/ubsan_type_hash.cc
> b/libsanitizer/ubsan/ubsan_type_hash.cc
> index d01009426db0..5eab1f561f27 100644
> --- a/libsanitizer/ubsan/ubsan_type_hash.cc
> +++ b/libsanitizer/ubsan/ubsan_type_hash.cc
> @@ -186,8 +186,8 @@ namespace {
>
> struct VtablePrefix {
> /// The offset from the vptr to the start of the most-derived object.
> - /// This should never be greater than zero, and will usually be exactly
> - /// zero.
> + /// This will only be greater than zero in some virtual base class vtables
> + /// used during object con-/destruction, and will usually be exactly zero.
> sptr Offset;
> /// The type_info object describing the most-derived class type.
> std::type_info *TypeInfo;
> @@ -197,7 +197,7 @@ VtablePrefix *getVtablePrefix(void *Object) {
> if (!*VptrPtr)
> return 0;
> VtablePrefix *Prefix = *VptrPtr - 1;
> - if (Prefix->Offset > 0 || !Prefix->TypeInfo)
> + if (!Prefix->TypeInfo)
> // This can't possibly be a valid vtable.
> return 0;
> return Prefix;
> --
> 2.5.1
>
> --
> Markus
Jakub
