From 31ae5fe02130be1ad9b15fac0d61e85970d6baf9 Mon Sep 17 00:00:00 2001
From: "copilot-swe-agent[bot]" <198982749+Copilot@users.noreply.github.com>
Date: Thu, 23 Jul 2026 10:17:31 +0000
Subject: [PATCH] C++: Implement \cX control escapes

---
 .../code/cpp/regex/internal/ParseRegExp.qll       |  5 ++++-
 cpp/ql/test/library-tests/regex/parse.expected    | 15 +++------------
 cpp/ql/test/library-tests/regex/regexp.expected   | 13 ++++---------
 3 files changed, 11 insertions(+), 22 deletions(-)

diff --git a/cpp/ql/lib/semmle/code/cpp/regex/internal/ParseRegExp.qll b/cpp/ql/lib/semmle/code/cpp/regex/internal/ParseRegExp.qll
index c84091b063f..191d91990da 100644
--- a/cpp/ql/lib/semmle/code/cpp/regex/internal/ParseRegExp.qll
+++ b/cpp/ql/lib/semmle/code/cpp/regex/internal/ParseRegExp.qll
@@ -344,8 +344,11 @@ abstract class RegExp extends StringLiteral {
       // wide hex char \uhhhh
       this.getChar(start + 1) = "u" and end = start + 6
       or
+      // control char \cX
+      this.getChar(start + 1) = "c" and end = start + 3
+      or
       // escape not handled above; update when adding a new case
-      not this.getChar(start + 1) in ["x", "u"] and
+      not this.getChar(start + 1) in ["x", "u", "c"] and
       not exists(this.getChar(start + 1).toInt()) and
       end = start + 2
     )
diff --git a/cpp/ql/test/library-tests/regex/parse.expected b/cpp/ql/test/library-tests/regex/parse.expected
index 0f07ba72809..b2f12c744a0 100644
--- a/cpp/ql/test/library-tests/regex/parse.expected
+++ b/cpp/ql/test/library-tests/regex/parse.expected
@@ -26,13 +26,9 @@
 
 #-----| [RegExpConstant, RegExpNormalChar] b
 
-#-----| [RegExpConstant, RegExpEscape] \c
+#-----| [RegExpConstant, RegExpEscape] \cZ
 
-#-----| [RegExpConstant, RegExpNormalChar] Z
-
-#-----| [RegExpConstant, RegExpEscape] \c
-
-#-----| [RegExpConstant, RegExpNormalChar] A
+#-----| [RegExpConstant, RegExpEscape] \cA
 
 #-----| [RegExpConstant, RegExpEscape] \u{987
 
@@ -171,10 +167,6 @@
 #-----| 1 -> [RegExpConstant, RegExpEscape] \n
 #-----| 2 -> [RegExpConstant, RegExpNormalChar] b
 
-#-----| [RegExpSequence] \cA
-#-----| 0 -> [RegExpConstant, RegExpEscape] \c
-#-----| 1 -> [RegExpConstant, RegExpNormalChar] A
-
 #-----| [RegExpSequence] [[:alpha:]][[:digit:]]
 #-----| 0 -> [RegExpCharacterClass] [[:alpha:]]
 #-----| 1 -> [RegExpCharacterClass] [[:digit:]]
@@ -292,8 +284,7 @@
 #-----| 1 -> [RegExpConstant, RegExpNormalChar] 9
 
 #-----| [RegExpCharacterClass] [\cZ]
-#-----| 0 -> [RegExpConstant, RegExpEscape] \c
-#-----| 1 -> [RegExpConstant, RegExpNormalChar] Z
+#-----| 0 -> [RegExpConstant, RegExpEscape] \cZ
 
 #-----| [RegExpCharacterClass] [A-F[:digit:]a-f]
 #-----| 0 -> [RegExpCharacterRange] A-F
diff --git a/cpp/ql/test/library-tests/regex/regexp.expected b/cpp/ql/test/library-tests/regex/regexp.expected
index 3f3c8b64604..0a5cfb87b6b 100644
--- a/cpp/ql/test/library-tests/regex/regexp.expected
+++ b/cpp/ql/test/library-tests/regex/regexp.expected
@@ -32,7 +32,6 @@ term
 | file://:0:0:0:0 | A | RegExpConstant,RegExpNormalChar |
 | file://:0:0:0:0 | A | RegExpConstant,RegExpNormalChar |
 | file://:0:0:0:0 | A | RegExpConstant,RegExpNormalChar |
-| file://:0:0:0:0 | A | RegExpConstant,RegExpNormalChar |
 | file://:0:0:0:0 | A-F | RegExpCharacterRange |
 | file://:0:0:0:0 | A-F | RegExpCharacterRange |
 | file://:0:0:0:0 | A-F] | RegExpConstant,RegExpNormalChar |
@@ -40,7 +39,6 @@ term
 | file://:0:0:0:0 | F | RegExpConstant,RegExpNormalChar |
 | file://:0:0:0:0 | F | RegExpConstant,RegExpNormalChar |
 | file://:0:0:0:0 | Z | RegExpConstant,RegExpNormalChar |
-| file://:0:0:0:0 | Z | RegExpConstant,RegExpNormalChar |
 | file://:0:0:0:0 | [ | RegExpConstant,RegExpNormalChar |
 | file://:0:0:0:0 | [123] | RegExpCharacterClass |
 | file://:0:0:0:0 | [A-F[:digit:]a-f] | RegExpCharacterClass |
@@ -70,9 +68,8 @@ term
 | file://:0:0:0:0 | \\] | RegExpConstant,RegExpEscape |
 | file://:0:0:0:0 | \\b | RegExpSpecialChar |
 | file://:0:0:0:0 | \\b!a\\B | RegExpSequence |
-| file://:0:0:0:0 | \\c | RegExpConstant,RegExpEscape |
-| file://:0:0:0:0 | \\c | RegExpConstant,RegExpEscape |
-| file://:0:0:0:0 | \\cA | RegExpSequence |
+| file://:0:0:0:0 | \\cA | RegExpConstant,RegExpEscape |
+| file://:0:0:0:0 | \\cZ | RegExpConstant,RegExpEscape |
 | file://:0:0:0:0 | \\d | RegExpCharacterClassEscape |
 | file://:0:0:0:0 | \\d\\D | RegExpSequence |
 | file://:0:0:0:0 | \\n | RegExpConstant,RegExpEscape |
@@ -167,20 +164,18 @@ regExpNormalCharValue
 | file://:0:0:0:0 | A | A |
 | file://:0:0:0:0 | A | A |
 | file://:0:0:0:0 | A | A |
-| file://:0:0:0:0 | A | A |
 | file://:0:0:0:0 | A-F] | A-F] |
 | file://:0:0:0:0 | F | F |
 | file://:0:0:0:0 | F | F |
 | file://:0:0:0:0 | Z | Z |
-| file://:0:0:0:0 | Z | Z |
 | file://:0:0:0:0 | [ | [ |
 | file://:0:0:0:0 | \\D | D |
 | file://:0:0:0:0 | \\S | S |
 | file://:0:0:0:0 | \\W | W |
 | file://:0:0:0:0 | \\[ | [ |
 | file://:0:0:0:0 | \\] | ] |
-| file://:0:0:0:0 | \\c | c |
-| file://:0:0:0:0 | \\c | c |
+| file://:0:0:0:0 | \\cA | cA |
+| file://:0:0:0:0 | \\cZ | cZ |
 | file://:0:0:0:0 | \\d | d |
 | file://:0:0:0:0 | \\n | \n |
 | file://:0:0:0:0 | \\n | \n |