<regex>: Avoid allocating during matching when regex defines no captures
#5518
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StephanTLavavej
added
performance
StephanTLavavej
approved these changes
May 20, 2025
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I'm mirroring this to the MSVC-internal repo - please notify me if any further changes are pushed. |
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muellerj2
deleted the
regex-no-allocations-during-matching-of-regexes-without-captures
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There is no need to allocate the capture group vectors in the matcher state when the only capture group is 0, because capture group 0 is just the whole match and we already know the bounds of the whole match (start is the position where
_Matcher2::_Matchwas called, end is the value of_Curin the matcher state).I can't come up with any additional test cases that should be added for this change and I think the existing test coverage should already catch it if I made a mistake here.
Benchmark on my machine: