[Bug libstdc++/110974] format out of bounds read on invalid format string "{:{}."

[gcc at pauldreik dot se via Gcc-bugs]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=110974

--- Comment #1 from Paul Dreik <gcc at pauldreik dot se> ---
This is very similar to https://gcc.gnu.org/bugzilla/show_bug.cgi?id=110862
which has already been fixed on trunk.