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