On Fri, May 18, 2018 at 9:53 AM, Jakub Jelinek <ja...@redhat.com> wrote:
> On Fri, May 18, 2018 at 09:02:08AM -0400, Nathan Sidwell wrote:
>> On 05/18/2018 08:53 AM, Marc Glisse wrote:
>>
>> > As long as you do not dereference ptr in the constructor, that shouldn't
>> > contradict 'restrict'. The PR gives this quote from the standard:
>> >
>> > "During the construction of an object, if the value of the object or any
>> > of its subobjects is accessed through a glvalue that is not obtained,
>> > directly or indirectly, from the constructor’s this pointer, the value
>> > of the object or subobject thus obtained is unspecified."
>> >
>> > which reads quite close to saying that 'this' is restrict.
>> Indeed it is, thanks.
>>
>> what about comparisons to this? I thought restrict implied such a
>> comparison was 'never the same'?
>>
>> ie. if the ctor was:
>> selfie (selfie *ptr) : me (ptr==this ? 0 : ptr) {}
>
> But what is invalid on:
> struct S { int foo (S *); int a; } s { 2 };
> int S::foo (S *x)
> {
> int b = this->a;
> x->a = 5;
> b += this->a;
> return b;
> }
> int main ()
> {
> if (s.foo (&s) != 7)
> abort ();
> }
>
> I think if you make this a restrict pointer, this will be miscompiled.
We're only talking about the 'this' pointer in a constructor, not a
normal member function like foo.
Jason
