[Bug tree-optimization/100366] spurious warning - std::vector::clear followed by std::vector::insert(vec.end(), ...) with -O2

[mrsam--- via Gcc-bugs]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=100366

--- Comment #3 from Sam Varshavchik <mr...@courier-mta.com> ---
If the warning is justified then something else isn't adding up.

I double-checked (with cppreference.com) something that I was pretty sure of:
and an insert() at the end() iterator is valid. The insert()ed range is valid.
If the C++ code is UB, or even potentially UB, I don't see it.