https://gcc.gnu.org/bugzilla/show_bug.cgi?id=86908
--- Comment #9 from Jonathan Wakely <redi at gcc dot gnu.org> --- (In reply to Kostya Frumkin from comment #8) > At the same time this design pattern (strategy) with placement-new is more > efficient than with common new. That's fine, but you can't use &strategy to access the AStrategy object you created at that position. You have several choices: - use an untyped buffer and create objects in there: alignas(AStrategy) unsigned char buf[sizeof(AStrategy)]; - use std::launder - use the pointer returned by the placement new-expression, which has the right type There are ways to do this safely in C++ today, but your original code is not one of those ways. You should fix your code. > So it has no rationale if the base methods > are used when using placement-new. At the same time other compilers > generates code where the derived method is callsed after placement-new. It's undefined behaviour, so anything can happen.
