https://gcc.gnu.org/bugzilla/show_bug.cgi?id=94325
--- Comment #7 from CVS Commits <cvs-commit at gcc dot gnu.org> --- The releases/gcc-9 branch has been updated by Jakub Jelinek <ja...@gcc.gnu.org>: https://gcc.gnu.org/g:175f052446556d32e887e1658a5a92c3c2f3a6f5 commit r9-8875-g175f052446556d32e887e1658a5a92c3c2f3a6f5 Author: Jakub Jelinek <ja...@redhat.com> Date: Wed Apr 8 15:30:16 2020 +0200 c++: Further fix for -fsanitize=vptr [PR94325] For -fsanitize=vptr, we insert a NULL store into the vptr instead of just adding a CLOBBER of this. build_clobber_this makes the CLOBBER conditional on in_charge (implicit) parameter whenever CLASSTYPE_VBASECLASSES, but when adding this conditionalization to the -fsanitize=vptr code in PR87095, I wanted it to catch some more cases when the class has CLASSTYPE_VBASECLASSES, but the vptr is still not shared with something else, otherwise the sanitization would be less effective. The following testcase shows that the chosen test that CLASSTYPE_PRIMARY_BINFO is non-NULL and has BINFO_VIRTUAL_P set wasn't sufficient, the D class has still sizeof(D) == sizeof(void*) and thus contains just a single vptr, but while in B::~B() this results in the vptr not being cleared, in C::~C() this condition isn't true, as CLASSTYPE_PRIMARY_BINFO in that case is B and is not BINFO_VIRTUAL_P, so it clears the vptr, but the D::~D() dtor after invoking C::~C() invokes A::~A() with an already cleared vptr, which is then reported. The following patch is just a shot in the dark, keep looking through CLASSTYPE_PRIMARY_BINFO until we find BINFO_VIRTUAL_P, but it works on the existing testcase as well as this new one. 2020-04-08 Jakub Jelinek <ja...@redhat.com> PR c++/94325 * decl.c (begin_destructor_body): For CLASSTYPE_VBASECLASSES class dtors, if CLASSTYPE_PRIMARY_BINFO is non-NULL, but not BINFO_VIRTUAL_P, look at CLASSTYPE_PRIMARY_BINFO of its BINFO_TYPE if it is not BINFO_VIRTUAL_P, and so on. * g++.dg/ubsan/vptr-15.C: New test. (cherry picked from commit 4cf6b06cb5b02c053738e2975e3b7a4b3c577401)
