[cfe-dev] Why the argument of `delete' is converted to void* ?

[John McCall]

On Jul 4, 2012, at 10:13 AM, Enea Zaffanella wrote:
> On 07/04/2012 05:07 PM, Jean-Daniel Dupas wrote:
>> Le 4 juil. 2012 à 15:57, Enea Zaffanella a écrit :
> [...]
>>> Sorry for the misunderstanding, but the original question was not
>>> really meant to be restricted to classes having a trivial destructor
>>> (if you add a non-trivial destructor to class S then "delete ps" will
>>> call it, whereas "operator delete(ps)" will not).
>>> 
>>> To rephrase my question: since in the general case "delete ps" may
>>> also call the destructor, why is its argument (always) converted to void*?
>>> 
>>> Cheers,
>>> Enea.
>> 
>> 
>> AFAIK, even with a non trivial destructor, the code always end up
>> calling the operator delete(void *) to free the memory.
> 
> Yes, the argument of "operator delete" has to be converted to a void*.
> 
> But this, afaict, is an inner implementation detail that should not be 
> exposed in the AST (or it should be exposed elsewhere, e.g., in a method 
> named getOperatorDeleteArg).
> 
> The argument of the CXXDeleteExpr is *not* subject to such an implicit 
> conversion; as a matter of fact, the implicit conversion (if made 
> explicit by the user) would change the semantics of the delete 
> expression by killing the call of the destructor.

It's a bug in the AST;  Sema is doing an implicit conversion to void* in order
to not have to implement custom logic for deleting values of record type, but
it should at least be dropping the extra ICE when it does so.  IR-generation
has to awkwardly work around this.

John.