<regex>: Should regex_match() use the match_results allocator?

[StephanTLavavej]

Reported by https://stackoverflow.com/questions/58399158/use-custom-allocator-for-stdregex-match .

Calling regex_match() or regex_search() with a match_results containing a custom allocator ends up constructing ordinary vector containers in _Matcher, specifically:

https://github.com/microsoft/STL/blob/6aa3b02fde6f885581279ff28d7a6b4f3e38fcb7/stl/inc/regex#L1650-L1652

The Standard is silent on this topic, but libc++ uses the match_results allocator here.

It may be possible to fix this while preserving ABI, by renaming _Matcher (which is a large but internal helper class).

Note: <regex> mostly ignores the existence of allocators; see LWG-1396 "regex should support allocators" and LWG-2216 "regex_replace(basic_string) allocator handling" for examples.

[DJLink]

Hi,

Ok so apologies if this probably has nothing to do with this, but I'm posting because I feel it could somehow be related.

I'm working on a project that has global new /free operator overloads. Recently regex_match() was added, and now this causes a crash on exit. After a bit of searching, and from what I could understand, regex_match internally we will now use our allocator via global new etc. However if seems that facets template somehow only deletes some things much later on when terminating program? Now it tries to delete but custom allocator is already gone and crash.

So the question really is, would allowing a custom allocator to match_results somehow work for this, in this case actually forcing a std::malloc use so it can safely free whenever it chooses to? or any other way to do this. Again sorry if this is not related.

Thanks.