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<regex>: Process negative lookahead assertions non-recursively #5734

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Merged
StephanTLavavej merged 1 commit into from
Sep 25, 2025
Merged

<regex>: Process negative lookahead assertions non-recursively #5734

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37 changes: 21 additions & 16 deletions stl/inc/regex
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Original file line number Diff line number Diff line change
Expand Up @@ -1674,7 +1674,10 @@ public:
}
};

enum class _Rx_unwind_ops { _After_assert = _N_end + 1 };
enum class _Rx_unwind_ops {
_After_assert = _N_end + 1,
_After_neg_assert,
};

template <class _BidIt>
class _Rx_state_frame_t {
Expand Down Expand Up @@ -1807,7 +1810,6 @@ private:
void _Increase_stack_usage_count();
void _Decrease_stack_usage_count();

bool _Do_neg_assert(_Node_assert*);
bool _Do_if(_Node_if*);
bool _Do_rep0(_Node_rep*, bool);
bool _Do_rep(_Node_rep*, bool, int);
Expand Down Expand Up @@ -3400,19 +3402,6 @@ void _Matcher3<_BidIt, _Elem, _RxTraits, _It, _Alloc>::_Decrease_stack_usage_cou
}
}

template <class _BidIt, class _Elem, class _RxTraits, class _It, class _Alloc>
bool _Matcher3<_BidIt, _Elem, _RxTraits, _It, _Alloc>::_Do_neg_assert(_Node_assert* _Node) {
// apply negative assert node
const size_t _Frame_idx = _Push_frame();
bool _Succeeded = !_Match_pat(_Node->_Child);
if (_Succeeded) {
const _Bt_state_t<_It>& _St = _Frames[_Frame_idx]._Match_state;
_Tgt_state = _St;
}
_Pop_frame(_Frame_idx);
return _Succeeded;
}

template <class _BidIt, class _Elem, class _RxTraits, class _It, class _Alloc>
bool _Matcher3<_BidIt, _Elem, _RxTraits, _It, _Alloc>::_Do_if(_Node_if* _Node) { // apply if node
const size_t _Frame_idx = _Push_frame();
Expand Down Expand Up @@ -4130,7 +4119,11 @@ bool _Matcher3<_BidIt, _Elem, _RxTraits, _It, _Alloc>::_Match_pat(_Node_base* _N

case _N_neg_assert:
{ // check negative assert
_Failed = !_Do_neg_assert(static_cast<_Node_assert*>(_Nx));
auto _Node = static_cast<_Node_assert*>(_Nx);
_Push_frame(_Rx_unwind_ops::_After_neg_assert, _Node);
_Next = _Node->_Child;

_Increase_stack_usage_count();
break;
}

Expand Down Expand Up @@ -4256,6 +4249,18 @@ bool _Matcher3<_BidIt, _Elem, _RxTraits, _It, _Alloc>::_Match_pat(_Node_base* _N
break;
}

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

default:
#if _ITERATOR_DEBUG_LEVEL != 0
_STL_REPORT_ERROR("internal stack of regex matcher corrupted");
Expand Down