https://gcc.gnu.org/bugzilla/show_bug.cgi?id=96996
Jonathan Wakely <redi at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Component|web |c++
Keywords| |missed-optimization
--- Comment #1 from Jonathan Wakely <redi at gcc dot gnu.org> ---
(In reply to Matthijs Kooijman from comment #0)
> There is still the caveat of "during its lifetime", IOW, what if you would
> destroy the object and create a new one it is place. However, see
> https://gcc.gnu.org/bugzilla/show_bug.cgi?id=80794#c5 for a discussion of
> this case. In short, replacing non_constant_test with a new object is
> possible, but only when it "does not contain any non-static data member
> whose type is const-qualified or a reference type", which does not hold for
> this object.
That's not quite accurate. Replacing non_constant_test with a new object is
possible, and allowed. But the name "non_constant_test" cannot be used to refer
to the new object, so any calls to non_constant_ref() after the object was
replaced would have undefined behaviour. Which means the compiler can assume
there are no such calls.
I'm not saying the optimization would be invalid, just clarifying what the
related discussion says.
