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<regex>: Perform simplified stack unwinding for lookahead assertions when the asserted pattern matches #5835

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Merged
merged 3 commits into from
Nov 12, 2025
+29 −13
Merged

<regex>: Perform simplified stack unwinding for lookahead assertions when the asserted pattern matches #5835

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aeecd09
`<regex>`: Perform simplified stack unwinding for lookahead assertion…
muellerj2 Nov 8, 2025
cb3c283
Remove unnecessary scope.
StephanTLavavej Nov 10, 2025
685121b
Make wrapping prettier.
StephanTLavavej Nov 10, 2025
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43 changes: 30 additions & 13 deletions stl/inc/regex
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Original file line number Diff line number Diff line change
Expand Up @@ -3919,7 +3919,28 @@ bool _Matcher3<_BidIt, _Elem, _RxTraits, _It, _Alloc>::_Match_pat(_Node_base* _N
}

case _N_end_assert:
_Next = nullptr;
{
for (;;) {
--_Frames_count;
const auto& _Frame = _Frames[_Frames_count];
const auto _Code = _Frame._Code;
if (_Code == _Rx_unwind_ops::_After_assert || _Code == _Rx_unwind_ops::_After_neg_assert) {
_Tgt_state._Cur = _Frame._Match_state._Cur;
_Decrease_stack_usage_count();
if (_Code == _Rx_unwind_ops::_After_assert) {
_Next = _Frame._Node->_Next;
} else {
_Failed = true;
}
break;
} else if (_Code == _Rx_unwind_ops::_Disjunction_eval_alt_on_failure
|| _Code == _Rx_unwind_ops::_Disjunction_eval_alt_always
|| _Code == _Rx_unwind_ops::_Loop_greedy || _Code == _Rx_unwind_ops::_Loop_nongreedy
|| _Code == _Rx_unwind_ops::_Loop_restore_vals) {
_Decrease_stack_usage_count();
}
}
}
break;

case _N_capture:
Expand Down Expand Up @@ -4184,24 +4205,20 @@ bool _Matcher3<_BidIt, _Elem, _RxTraits, _It, _Alloc>::_Match_pat(_Node_base* _N

switch (_Frame._Code) {
case _Rx_unwind_ops::_After_assert:
{ // positive assert completed
{ // matching pattern of positive assert failed
_STL_INTERNAL_CHECK(_Failed);
_Decrease_stack_usage_count();
if (!_Failed) {
_Tgt_state._Cur = _Frame._Match_state._Cur;
_Nx = _Frame._Node->_Next;
}
break;
}

case _Rx_unwind_ops::_After_neg_assert:
{ // negative assert completed
{ // matching pattern of negative assert failed
_STL_INTERNAL_CHECK(_Failed);
_Decrease_stack_usage_count();
if (_Failed) {
const _Bt_state_t<_It>& _St = _Frame._Match_state;
_Tgt_state = _St;
_Nx = _Frame._Node->_Next;
}
_Failed = !_Failed;
const _Bt_state_t<_It>& _St = _Frame._Match_state;
_Tgt_state = _St;
_Nx = _Frame._Node->_Next;
_Failed = false;
break;
}

Expand Down