[Bug libstdc++/103848] [11/12 Regression] std::deque<>::iterator operator- uses "0" for nullptr check, triggers "zero-as-null-pointer-constant" warning

[redi at gcc dot gnu.org via Gcc-bugs]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=103848

--- Comment #5 from Jonathan Wakely <redi at gcc dot gnu.org> ---
(In reply to Jonathan Wakely from comment #4)
> We get (T*)0 - 1 + 1 which overflows twice.

GCC's ubsan doesn't diagnose this, but Clang's does.