https://gcc.gnu.org/bugzilla/show_bug.cgi?id=109442
--- Comment #20 from Jonathan Wakely <redi at gcc dot gnu.org> ---
(In reply to Jan Hubicka from comment #19)
> Similar argument can IMO be used for eliding unused memory allocations. It
> is kind of up to std::vector implementation on how many
> allocations/deallocations it does, right?
It's up to std::allocator, which is not required to call operator new every
time memory is needed.
> So we need a way to annotate the new/delete calls in the standard library as
> safe for such optimizations (i.e. implement clang's
> __bulitin_operator_new/delete?)
Yes, see PR 110137.
> How clang manages to optimize this out without additional hinting?
It supports __builtin_operator_{new,delete} and libstdc++ uses that when
compiled with clang.
