Skip to content

<regex>: Successful negative lookahead assertions do not matche to capture groups #5269

New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Closed
wants to merge 4 commits into from
Closed

<regex>: Successful negative lookahead assertions do not matche to capture groups #5269

Changes from 1 commit
Commits
Show all changes
4 commits
Select commit Hold shift + click to select a range
8b5f972
capture groups in negative lookahead assertions are never matched
alexprabhatbara Feb 4, 2025
2a078d3
reset state after a successful negative assertion
alexprabhatbara Feb 5, 2025
331e2cb
revert penultimate commit change
alexprabhatbara Feb 5, 2025
82e96b6
necessary optimizations
alexprabhatbara Feb 7, 2025
File filter

Filter by extension

Filter by extension
Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
6 changes: 1 addition & 5 deletions stl/inc/regex
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -334,10 +334,7 @@ public:
template <class _Iter>
char_class_type lookup_classname(_Iter _First, _Iter _Last, bool _Icase = false) const {
// map [_First, _Last) to character class mask value
#define _REGEX_CHAR_CLASS_NAME(n, c) \
{ \
n, L##n, static_cast<unsigned int>(_STD size(n) - 1), c \
}
#define _REGEX_CHAR_CLASS_NAME(n, c) {n, L##n, static_cast<unsigned int>(_STD size(n) - 1), c}
static constexpr _Cl_names _Names[] = {
// map class names to numeric constants
_REGEX_CHAR_CLASS_NAME("alnum", _Ch_alnum),
Expand Down Expand Up @@ -3610,7 +3607,6 @@ bool _Matcher<_BidIt, _Elem, _RxTraits, _It>::_Match_pat(_Node_base* _Nx) { // c
_Node_end_group* _Node = static_cast<_Node_end_group*>(_Nx);
_Node_capture* _Node0 = static_cast<_Node_capture*>(_Node->_Back);
if (_Cap || _Node0->_Idx != 0) { // update capture data
_Tgt_state._Grp_valid[_Node0->_Idx] = true;
Copy link
Contributor

Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

This deletion does not just correct the matches for negative assertions. With this change, no capture group at all will ever be matched.

Changes to fix #5245 actually have to be applied here:

STL/stl/inc/regex

Lines 3575 to 3590 in fc15609

case _N_neg_assert:
case _N_assert:
{ // check assert
_It _Ch = _Tgt_state._Cur;
bool _Neg = _Nx->_Kind == _N_neg_assert;
_Bt_state_t<_It> _St = _Tgt_state;
if (_Match_pat(static_cast<_Node_assert*>(_Nx)->_Child) == _Neg) {
// restore initial state and indicate failure
_Tgt_state = _St;
_Failed = true;
} else {
_Tgt_state._Cur = _Ch;
}
break;
}

Specifically, _Tgt_state._Cur = _Ch; insufficiently resets the state after a successful negative assertion. (But it is the appropriate reset for positive assertions.)

Copy link
Contributor Author

Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

I have restored the initial state after a successful negative assertion.

_Tgt_state._Grps[_Node0->_Idx]._End = _Tgt_state._Cur;
}
break;
Expand Down
Loading