<regex>: Repair character class escapes outside character class definitions (#5160)

Co-authored-by: Stephan T. Lavavej <[email protected]>

Author: muellerj2

stl/inc/regex

@@ -1710,7 +1710,7 @@ private:
     bool _OctalDigits();
     void _Do_ex_class(_Meta_type);
     bool _CharacterClassEscape(bool);
-    _Prs_ret _ClassEscape(bool);
+    _Prs_ret _ClassEscape2();
     _Prs_ret _ClassAtom();
     void _ClassRanges();
     void _CharacterClass();
@@ -4017,22 +4017,29 @@ bool _Parser<_FwdIt, _Elem, _RxTraits>::_CharacterClassEscape(bool _Addit) { //
         return false;
     }
 
+    const bool _Negated = _Traits.isctype(_Char, _RxTraits::_Ch_upper);
     if (_Addit) {
         _Nfa._Add_class();
+        // GH-992: Outside character class definitions, _Cls completely defines the character class
+        // so negating _Cls and negating the entire character class are equivalent.
+        // Since the former negation is defective, do the latter instead.
+        if (_Negated) {
+            _Nfa._Negate();
+        }
     }
 
-    _Nfa._Add_named_class(_Cls, _Traits.isctype(_Char, _RxTraits::_Ch_upper));
+    _Nfa._Add_named_class(_Cls, _Negated && !_Addit);
     _Next();
     return true;
 }
 
 template <class _FwdIt, class _Elem, class _RxTraits>
-_Prs_ret _Parser<_FwdIt, _Elem, _RxTraits>::_ClassEscape(bool _Addit) { // check for class escape
+_Prs_ret _Parser<_FwdIt, _Elem, _RxTraits>::_ClassEscape2() { // check for class escape
     if ((_L_flags & _L_esc_bsl) && _Char == _Esc_bsl) { // handle escape backslash if allowed
         _Val = _Esc_bsl;
         _Next();
         return _Prs_chr;
-    } else if ((_L_flags & _L_esc_wsd) && _CharacterClassEscape(_Addit)) {
+    } else if ((_L_flags & _L_esc_wsd) && _CharacterClassEscape(false)) {
         return _Prs_set;
     } else if (_DecimalDigits(regex_constants::error_escape)) { // check for invalid value
         if (_Val != 0) {
@@ -4049,7 +4056,7 @@ _Prs_ret _Parser<_FwdIt, _Elem, _RxTraits>::_ClassAtom() { // check for class at
     if (_Mchar == _Meta_esc) { // check for valid escape sequence
         _Next();
         if (_L_flags & _L_grp_esc) {
-            return _ClassEscape(false);
+            return _ClassEscape2();
         } else if ((_L_flags & _L_esc_ffn && _Do_ffn(_Char))
                    || (_L_flags & _L_esc_ffnx && _Do_ffnx(_Char))) { // advance to next character
             _Next();

tests/std/tests/VSO_0000000_regex_use/test.cpp

@@ -659,6 +659,16 @@ void test_gh_5058() {
     }
 }
 
+void test_gh_5160() {
+    // GH-5160 fixed mishandled negated character class escapes
+    // outside character class definitions
+    const test_wregex neg_regex(&g_regexTester, LR"(Y\S*Z)");
+    neg_regex.should_search_match(L"xxxYxx\x0078xxxZxxx", L"Yxx\x0078xxxZ"); // U+0078 LATIN SMALL LETTER X
+    neg_regex.should_search_match(L"xxxYxx\x03C7xxxZxxx", L"Yxx\x03C7xxxZ"); // U+03C7 GREEK SMALL LETTER CHI
+    neg_regex.should_search_fail(L"xxxYxx xxxZxxx");
+    neg_regex.should_search_fail(L"xxxYxx\x2009xxxZxxx"); // U+2009 THIN SPACE
+}
+
 int main() {
     test_dev10_449367_case_insensitivity_should_work();
     test_dev11_462743_regex_collate_should_not_disable_regex_icase();
@@ -688,6 +698,7 @@ int main() {
     test_gh_993();
     test_gh_4995();
     test_gh_5058();
+    test_gh_5160();
 
     return g_regexTester.result();
 }