https://gcc.gnu.org/bugzilla/show_bug.cgi?id=92332
Jonathan Wakely <redi at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Status|WAITING |RESOLVED
Resolution|--- |INVALID
--- Comment #3 from Jonathan Wakely <redi at gcc dot gnu.org> ---
(In reply to Andrew Pinski from comment #1)
> two things,
> One is you are violating C++ aliasing rules I think.
Right, you're creating a uint64_t but accessing two uint32_t objects. The
uint32_t objects were never initialized, so have indeterminate values. That's
why you get warnings about uninitialized data.
It would work if you used an array of unsigned char or std::byte, since they
have special aliasing rules that allow them to be used to read the bytes of
other types.
Also the static_cast<bar&> is undefined, because there is no bar object at that
location, just a myarray<int32_t, 2>.
> Second is after "operator new", the value that is contained in the pointer
> is undefined/unspecified.
I don't know what this means.
> NOTE in C++2a (or c++20), there is an operator new which has the property of
> the value is kept defined. (BUT GCC Does not implement that yet).
I don't know what this means either.
The code has undefined behaviour though, so closing.
