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Atomic group must not increase stack depth#401

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mvorisek opened this issue Mar 22, 2024 · 1 comment
Open

Atomic group must not increase stack depth #401

mvorisek opened this issue Mar 22, 2024 · 1 comment

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@mvorisek
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mvorisek commented Mar 22, 2024 •
edited

Currently, when (?: (non-capturing group) is changes to (?> (atomic group), it increases stack usage causing JIT matching to fail with the following error:

JIT stack limit exhausted

This is problematic in deeply recursive regexes as it seems atomic group adds at least +1 stack depth per recursion.

I would expect this to be handled stackless.

Here is an example where we had to reduce atomic group usage to workaround this issue: mvorisek/PHP-CS-Fixer@fbce0f4
@zherczeg
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Depends on the pattern. Assertions and atomic blocks needs to be reverted when they fail. E.g: (?>(a))b this adds a capturing bracket, which needs to be reverted if b fails to match. Marks, start of match, etc. needs to be reverted as well. So entering to an atomic block / atomic assertion may trigger many variable savings. I remember the engine optimizes some simple cases, but this has limitations.

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@mvorisek @zherczeg