On Fri, Feb 19, 2016 at 01:04:04PM +0100, Petr Spacek wrote: > On 19.2.2016 08:50, Jakub Jelinek wrote: > > On Fri, Feb 19, 2016 at 03:12:29AM +0100, Kevin Kofler wrote: > >> Jakub Jelinek wrote: > >>> ASSERT(this) is pointless, it is testing if undefined behavior didn't > >>> happen after the fact, that is just too late. As I said, use > >>> -fsanitize=undefined to make sure you don't call methods on nullptr. > >> > >> Doesn't -fno-delete-null-pointer-checks make such ASSERTs work (and also > >> explicit "if (this)" type checks)? I read that that flag fixes programs > >> which rely on "if (this)" checks. > > > > That switch allows to work around buggy programs, at the cost of optimizing > > them less, yes. In any case, such programs should be fixed, this must be > > always non-NULL, methods can't be called on NULL pointers. > > Could you elaborate on this, please? > > What is wrong with > if (ptr != NULL) > ? > > What standard says that it is wrong? It's about checking whether "this", in C++, is NULL. Since any call on a null pointer is undefined behavior, any code relying on such checks is non-standard. Marek -- devel mailing list devel@xxxxxxxxxxxxxxxxxxxxxxx http://lists.fedoraproject.org/admin/lists/devel@xxxxxxxxxxxxxxxxxxxxxxx
