Re: [PATCH] c++: End lifetime of objects in constexpr after destructor call [PR71093]

[Richard Biener <rguenther@suse.de>]

> Am 10.12.2023 um 12:21 schrieb Alexander Monakov <amonakov@ispras.ru>:
> 
> 
> On Sun, 10 Dec 2023, Richard Biener wrote:
> 
>>> It seems wrong to me: CLOBBER_EOL is documented to mean that the storage is
>>> expiring at that point as well, which a (pseudo-)destructor does not imply;
>>> it's perfectly valid to destroy an object and then create another in the
>>> same storage.
>>> 
>>> We probably do want another clobber kind for end of object lifetime. And/or
>>> one for beginning of object lifetime.
>> 
>> There’s not much semantically different between UNDEF and end of object but
>> not storage lifetime?  At least for what middle-end optimizations do.
>> 
>> EOL is used by stack slot sharing and that operates on the underlying storage,
>> not individual objects live in it.
> 
> I thought EOL implies that ASan may poison underlying memory. In the respin
> of the Valgrind interop patch we instrument CLOBBER_UNDEF, but not CLOBBER_EOL.

EOL is like free (), while UNDEF is more
Like malloc ().

Richard 


> Alexander