C++23: labels at the end of compound statements

- [P2324R2](https://wg21.link/P2324R2) - linked to SonarOpenCommunity#2536
guwirth · Sep 2, 2024 · 8d13a91 · 8d13a91
1 parent 0a8339b
commit 8d13a91
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Showing 4 changed files with 47 additions and 33 deletions.
diff --git a/cxx-squid/dox/diff-cpp20-cpp23_grammar.txt b/cxx-squid/dox/diff-cpp20-cpp23_grammar.txt
@@ -141,23 +141,6 @@ requirement-seq:
    requirement
    requirement requirement-seq
 
-**A.6 Statements [gram.stmt]**
-
-label:
-   attribute-specifier-seqopt identifier :
-   attribute-specifier-seqopt case constant-expression :
-   attribute-specifier-seqopt default :
-
-labeled-statement:
-   label statement
-
-compound-statement:
-   { statement-seqopt label-seqopt }
-
-label-seq:
-   label
-   label-seq label
-
 **A.7 Declarations [gram.dcl]**
 
 declaration:

diff --git a/cxx-squid/src/main/java/org/sonar/cxx/parser/CxxGrammarImpl.java b/cxx-squid/src/main/java/org/sonar/cxx/parser/CxxGrammarImpl.java
@@ -119,7 +119,9 @@ public enum CxxGrammarImpl implements GrammarRuleKey {
   expressionStatement,
   compoundStatement,
   statementSeq,
+  labelSeq,
   condition,
+  label,
   selectionStatement,
   iterationStatement,
   initStatement,
@@ -963,32 +965,40 @@ private static void statements(LexerfulGrammarBuilder b) {
       )
     );
 
-    b.rule(labeledStatement).is(
+    b.rule(label).is(
       b.firstOf(
-        b.sequence(b.optional(attributeSpecifierSeq), IDENTIFIER, ":", statement), // C++
+        b.sequence(b.optional(attributeSpecifierSeq), IDENTIFIER, ":"), // C++
         b.sequence(
           b.optional(attributeSpecifierSeq), CxxKeyword.CASE, constantExpression,
           b.firstOf(
-            b.sequence(":", statement), // C++
-            b.sequence("...", constantExpression, ":", statement) // EXTENSION: gcc's case range
+            ":", // C++
+            b.sequence("...", constantExpression, ":") // EXTENSION: gcc's case range
           )
         ),
-        b.sequence(b.optional(attributeSpecifierSeq), CxxKeyword.DEFAULT, ":", statement) // C++
+        b.sequence(b.optional(attributeSpecifierSeq), CxxKeyword.DEFAULT, ":") // C++
       )
     );
 
+    b.rule(labeledStatement).is(
+      label, statement
+    );
+
     b.rule(expressionStatement).is(
       b.optional(expression), ";" // C++
     );
 
     b.rule(compoundStatement).is(
-      "{", b.optional(statementSeq), "}" // C++
+      "{", b.optional(statementSeq), b.optional(labelSeq), "}" // C++
     );
 
     b.rule(statementSeq).is(
       b.oneOrMore(statement) // C++
     );
 
+    b.rule(labelSeq).is(
+      b.oneOrMore(label) // C++
+    );
+
     b.rule(selectionStatement).is(
       b.firstOf(
         b.sequence(CxxKeyword.IF, b.optional(CxxKeyword.CONSTEXPR), "(", b.optional(initStatement), condition, ")",

diff --git a/cxx-squid/src/test/java/org/sonar/cxx/parser/StatementTest.java b/cxx-squid/src/test/java/org/sonar/cxx/parser/StatementTest.java
@@ -97,23 +97,23 @@ void selectionStatement_reallife() {
   }
 
   @Test
-  void labeledStatement() {
-    setRootRule(CxxGrammarImpl.labeledStatement);
+  void label() {
+    setRootRule(CxxGrammarImpl.label);
 
     mockRule(CxxGrammarImpl.attributeSpecifierSeq);
     mockRule(CxxGrammarImpl.statement);
     mockRule(CxxGrammarImpl.constantExpression);
 
     assertThatParser()
-      .matches("foo : statement")
-      .matches("attributeSpecifierSeq foo : statement")
-      .matches("case constantExpression : statement")
-      .matches("attributeSpecifierSeq case constantExpression : statement")
-      .matches("default : statement")
-      .matches("attributeSpecifierSeq default : statement")
+      .matches("foo :")
+      .matches("attributeSpecifierSeq foo :")
+      .matches("case constantExpression :")
+      .matches("attributeSpecifierSeq case constantExpression :")
+      .matches("default :")
+      .matches("attributeSpecifierSeq default :")
       // EXTENSION: gcc's case range
-      .matches("case constantExpression ... constantExpression : statement")
-      .matches("attributeSpecifierSeq case constantExpression ... constantExpression : statement");
+      .matches("case constantExpression ... constantExpression :")
+      .matches("attributeSpecifierSeq case constantExpression ... constantExpression :");
   }
 
   @Test
@@ -127,6 +127,17 @@ void statementSeq() {
       .matches("statement statement");
   }
 
+  @Test
+  void labelSeq() {
+    setRootRule(CxxGrammarImpl.labelSeq);
+
+    mockRule(CxxGrammarImpl.label);
+
+    assertThatParser()
+      .matches("label")
+      .matches("label label");
+  }
+
   @Test
   void selectionStatement() {
     setRootRule(CxxGrammarImpl.selectionStatement);

diff --git a/cxx-squid/src/test/resources/parser/own/C++23/labels-at-the-end.cc b/cxx-squid/src/test/resources/parser/own/C++23/labels-at-the-end.cc
@@ -0,0 +1,10 @@
+void foo()
+{
+ first: // allowed in C++, now also allowed in C
+    int x;
+
+ second: // allowed in both C++ and C
+    x = 1;
+
+ last: // C++23: now also allowed in C++
+}