[Bug c/71983] "error: initializer element is not constant" only with -O0

[k2k at narod dot ru]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=71983

--- Comment #2 from Karlson2k <k2k at narod dot ru> ---
clang and MSVC accept this code.
Inconsistency at different optimization levels is confusing and make harder to
reveal errors in code.