[Bug libstdc++/106248] [11/12/13 Regression] operator>>std::basic_istream at boundary condition behave differently in different opt levels

[redi at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=106248

--- Comment #5 from Jonathan Wakely <redi at gcc dot gnu.org> ---
(In reply to Andrew Pinski from comment #1)
> This is interesting because I get the same behavior in clang with LLVM's
> libc++.

Are you sure? I do not see any dependency on optimization level when using
libc++.

> Also with -std=c++20 I get the value 0 for all optimization levels.

I *do* see a change in behaviour for C++17 vs C++20 when using libc++, which is
expected for the reasons already given.