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Re: Optimizing away deletion of null pointers with g++


On 16 August 2017 at 15:27, Oleg Endo wrote:
> On Wed, 2017-08-16 at 13:30 +0200, Paolo Carlini wrote:
>>
>> I didn't understand why we don't already handle the easy case:
>>
>> constexpr int* ptr = nullptr;
>> delete ptr;
>>
>
> What about overriding the global delete operator with some user defined
> implementation?  Is there something in the C++ standard that says the
> invocation can be completely omitted, i.e. on which side of the call
> the nullptr check is being done?
>
> One possible use case could be overriding the global delete operator to
> count the number of invocations, incl. for nullptr.  Not sure how
> useful that is though.

Users can replace the deallocation function "operator delete" but this
is the delete operator ... a subtly different thing.

Anyway, the standard says:

"If the value of the operand of the delete-expression is a null
pointer value, it is unspecified whether a deallocation function will
be called as described above."

So it's permitted to omit the call to operator delete.


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