[Bug libstdc++/123901] Consider optimizing std::regex matching algos to convert [first,last) to a std::basic_string and match on that

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

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=123901

--- Comment #4 from Jonathan Wakely <redi at gcc dot gnu.org> ---
Yes, that seems convincing to me.

We could still consider lowering all contiguous iterators to const CharT*
pointers, so that we share the same instantiations for std::string::iterator
and std::string::const_iterator, and char* and const char*, and iterators into
vectors and spans. That wouldn't perform any allocations and wouldn't have any
effect on non-contiguous iterators (like your rope use case).

And then if we have a single instantiation for all matches on const char*
inputs, we could move that into a non-inline function defined inside the
library. That could potentially reduce the ABI impact of future optimizations
done in the regex executor.