On 19.2.2016 13:08, Marek Polacek wrote:
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
>>>> 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
>>> 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
pointer is undefined behavior, any code relying on such checks is non-standard.
Ah, okay. I was talking about pure C all the time, so I got confused :-)
Petr Spacek @ Red Hat