Merge pull request #1034 from github/michaelrfairhurst/package-deadcode-6

mbaluda · web-flow · commit b0e343f885f6 · 2026-02-19T13:59:43.000Z
Implement DeadCode6, RULE-0-1-2, shared with A0-1-2.
diff --git a/change_notes/2026-02-10-share-autosar-0-1-2.md b/change_notes/2026-02-10-share-autosar-0-1-2.md
@@ -0,0 +1,2 @@
+ - `A0-1-2` - `UnusedReturnValue.ql`:
+   - Refactors the rule implementation into a shared library for usage in MISRA C++ ruleset. No externally visible changes expected.
diff --git a/cpp/autosar/src/rules/A0-1-2/UnusedReturnValue.ql b/cpp/autosar/src/rules/A0-1-2/UnusedReturnValue.ql
@@ -16,35 +16,10 @@
 
 import cpp
 import codingstandards.cpp.autosar
-import codingstandards.cpp.Operator
-import cpp
+import codingstandards.cpp.rules.unusedreturnvalueshared.UnusedReturnValueShared
 
-/*
- * This query performs a simple syntactic check to ensure that the return value of the function is
- * not completely ignored. This matches the examples given in the rule, although the text itself is
- * not entirely clear. This means it will not find cases where something is done with the return
- * value, but it is not meaningfully read. For example: `int ret_val = f();`, with no subsequent
- * access of `ret_val`. However, such a case _would_ be flagged by A0-1-1 - Useless assignment.
- */
+module UnusedReturnValueConfig implements UnusedReturnValueSharedConfigSig {
+  Query getQuery() { result = DeadCodePackage::unusedReturnValueQuery() }
+}
 
-from FunctionCall fc, Function f
-where
-  not isExcluded(fc, DeadCodePackage::unusedReturnValueQuery()) and
-  // Find function calls in `ExprStmt`s, which indicate the return value is ignored
-  fc.getParent() instanceof ExprStmt and
-  // Ignore calls to void functions, which don't return values
-  not fc.getUnderlyingType() instanceof VoidType and
-  // Get the function target
-  f = fc.getTarget() and
-  // Overloaded (i.e. user defined) operators should behave in the same way as built-in operators,
-  // so the rule does not require the use of the return value
-  not f instanceof Operator and
-  // Exclude cases where the function call is generated within a macro, as the user of the macro is
-  // not necessarily able to address those results
-  not fc.isAffectedByMacro() and
-  // Rule allows disabling this rule where a static_cast<void> or a C-style cast to void is applied
-  not exists(Cast cast | cast instanceof StaticCast or cast instanceof CStyleCast |
-    fc.getExplicitlyConverted() = cast and
-    cast.getActualType() instanceof VoidType
-  )
-select fc, "Return value from call to $@ is unused.", f, f.getName()
+import UnusedReturnValueShared<UnusedReturnValueConfig>
diff --git a/cpp/autosar/test/rules/A0-1-2/UnusedReturnValue.expected b/cpp/autosar/test/rules/A0-1-2/UnusedReturnValue.expected
diff --git a/cpp/autosar/test/rules/A0-1-2/UnusedReturnValue.qlref b/cpp/autosar/test/rules/A0-1-2/UnusedReturnValue.qlref
diff --git a/cpp/autosar/test/rules/A0-1-2/UnusedReturnValue.testref b/cpp/autosar/test/rules/A0-1-2/UnusedReturnValue.testref
@@ -0,0 +1 @@
+cpp/common/test/rules/unusedreturnvalueshared/UnusedReturnValueShared.ql
diff --git a/cpp/common/src/codingstandards/cpp/exclusions/cpp/DeadCode6.qll b/cpp/common/src/codingstandards/cpp/exclusions/cpp/DeadCode6.qll
@@ -0,0 +1,26 @@
+//** THIS FILE IS AUTOGENERATED, DO NOT MODIFY DIRECTLY.  **/
+import cpp
+import RuleMetadata
+import codingstandards.cpp.exclusions.RuleMetadata
+
+newtype DeadCode6Query = TUnusedReturnValueMisraCppQuery()
+
+predicate isDeadCode6QueryMetadata(Query query, string queryId, string ruleId, string category) {
+  query =
+    // `Query` instance for the `unusedReturnValueMisraCpp` query
+    DeadCode6Package::unusedReturnValueMisraCppQuery() and
+  queryId =
+    // `@id` for the `unusedReturnValueMisraCpp` query
+    "cpp/misra/unused-return-value-misra-cpp" and
+  ruleId = "RULE-0-1-2" and
+  category = "required"
+}
+
+module DeadCode6Package {
+  Query unusedReturnValueMisraCppQuery() {
+    //autogenerate `Query` type
+    result =
+      // `Query` type for `unusedReturnValueMisraCpp` query
+      TQueryCPP(TDeadCode6PackageQuery(TUnusedReturnValueMisraCppQuery()))
+  }
+}
diff --git a/cpp/common/src/codingstandards/cpp/exclusions/cpp/RuleMetadata.qll b/cpp/common/src/codingstandards/cpp/exclusions/cpp/RuleMetadata.qll
@@ -19,6 +19,7 @@ import Conversions2
 import DeadCode
 import DeadCode3
 import DeadCode4
+import DeadCode6
 import Declarations
 import ExceptionSafety
 import Exceptions1
@@ -91,6 +92,7 @@ newtype TCPPQuery =
   TDeadCodePackageQuery(DeadCodeQuery q) or
   TDeadCode3PackageQuery(DeadCode3Query q) or
   TDeadCode4PackageQuery(DeadCode4Query q) or
+  TDeadCode6PackageQuery(DeadCode6Query q) or
   TDeclarationsPackageQuery(DeclarationsQuery q) or
   TExceptionSafetyPackageQuery(ExceptionSafetyQuery q) or
   TExceptions1PackageQuery(Exceptions1Query q) or
@@ -163,6 +165,7 @@ predicate isQueryMetadata(Query query, string queryId, string ruleId, string cat
   isDeadCodeQueryMetadata(query, queryId, ruleId, category) or
   isDeadCode3QueryMetadata(query, queryId, ruleId, category) or
   isDeadCode4QueryMetadata(query, queryId, ruleId, category) or
+  isDeadCode6QueryMetadata(query, queryId, ruleId, category) or
   isDeclarationsQueryMetadata(query, queryId, ruleId, category) or
   isExceptionSafetyQueryMetadata(query, queryId, ruleId, category) or
   isExceptions1QueryMetadata(query, queryId, ruleId, category) or
diff --git a/cpp/common/src/codingstandards/cpp/rules/unusedreturnvalueshared/UnusedReturnValueShared.qll b/cpp/common/src/codingstandards/cpp/rules/unusedreturnvalueshared/UnusedReturnValueShared.qll
@@ -0,0 +1,47 @@
+/**
+ * Provides a configurable module UnusedReturnValue with a `problems` predicate
+ * for the following issue:
+ * The value returned by a function having a non-void return type that is not an
+ * overloaded operator shall be used.
+ */
+
+import cpp
+import codingstandards.cpp.Customizations
+import codingstandards.cpp.Exclusions
+
+signature module UnusedReturnValueSharedConfigSig {
+  Query getQuery();
+}
+
+module UnusedReturnValueShared<UnusedReturnValueSharedConfigSig Config> {
+  /*
+   * This query performs a simple syntactic check to ensure that the return value of the function is
+   * not completely ignored. This matches the examples given in the rule, although the text itself is
+   * not entirely clear. This means it will not find cases where something is done with the return
+   * value, but it is not meaningfully read. For example: `int ret_val = f();`, with no subsequent
+   * access of `ret_val`. However, such a case _would_ be flagged by A0-1-1 - Useless assignment.
+   */
+
+  query predicate problems(FunctionCall fc, string message, Function f, string funcName) {
+    not isExcluded(fc, Config::getQuery()) and
+    message = "Return value from call to $@ is unused." and
+    funcName = f.getName() and
+    // Find function calls in `ExprStmt`s, which indicate the return value is ignored
+    fc.getParent() instanceof ExprStmt and
+    // Ignore calls to void functions, which don't return values
+    not fc.getUnderlyingType() instanceof VoidType and
+    // Get the function target
+    f = fc.getTarget() and
+    // Overloaded (i.e. user defined) operators should behave in the same way as built-in operators,
+    // so the rule does not require the use of the return value
+    not f instanceof Operator and
+    // Exclude cases where the function call is generated within a macro, as the user of the macro is
+    // not necessarily able to address those results
+    not fc.isAffectedByMacro() and
+    // Rule allows disabling this rule where a static_cast<void> or a C-style cast to void is applied
+    not exists(Cast cast | cast instanceof StaticCast or cast instanceof CStyleCast |
+      fc.getExplicitlyConverted() = cast and
+      cast.getActualType() instanceof VoidType
+    )
+  }
+}
diff --git a/cpp/common/test/deviations/deviation_permits_basic_test/UnusedReturnValue.ql b/cpp/common/test/deviations/deviation_permits_basic_test/UnusedReturnValue.ql
@@ -17,31 +17,11 @@
 import cpp
 import codingstandards.cpp.CodingStandards
 import codingstandards.cpp.exclusions.cpp.RuleMetadata
+import codingstandards.cpp.rules.unusedreturnvalueshared.UnusedReturnValueShared
 
 /* This is a copy of an AUTOSAR rule, which we are using for testing purposes. */
-/*
- * This query performs a simple syntactic check to ensure that the return value of the function is
- * not completely ignored. This matches the examples given in the rule, although the text itself is
- * not entirely clear. This means it will not find cases where something is done with the return
- * value, but it is not meaningfully read. For example: `int ret_val = f();`, with no subsequent
- * access of `ret_val`. However, such a case _would_ be flagged by A0-1-1 - Useless assignment.
- */
+module UnusedReturnValueConfig implements UnusedReturnValueSharedConfigSig {
+  Query getQuery() { result = DeadCodePackage::unusedReturnValueQuery() }
+}
 
-from FunctionCall fc, Function f
-where
-  not isExcluded(fc, DeadCodePackage::unusedReturnValueQuery()) and
-  // Find function calls in `ExprStmt`s, which indicate the return value is ignored
-  fc.getParent() instanceof ExprStmt and
-  // Ignore calls to void functions, which don't return values
-  not fc.getType() instanceof VoidType and
-  // Get the function target
-  f = fc.getTarget() and
-  // Overloaded (i.e. user defined) operators should behave in the same way as built-in operators,
-  // so the rule does not require the use of the return value
-  not f instanceof Operator and
-  // Exclude cases where the function call is generated within a macro, as the user of the macro is
-  // not necessarily able to address thoes results
-  not fc.isAffectedByMacro() and
-  // Rule allows disabling this rule where a static_cast<void> is applied
-  not fc.getExplicitlyConverted().(StaticCast).getActualType() instanceof VoidType
-select fc, "Return value from call to $@ is unused.", f, f.getName()
+import UnusedReturnValueShared<UnusedReturnValueConfig>
diff --git a/cpp/common/test/deviations/deviations_basic_test/UnusedReturnValue.ql b/cpp/common/test/deviations/deviations_basic_test/UnusedReturnValue.ql
@@ -17,31 +17,11 @@
 import cpp
 import codingstandards.cpp.CodingStandards
 import codingstandards.cpp.exclusions.cpp.RuleMetadata
+import codingstandards.cpp.rules.unusedreturnvalueshared.UnusedReturnValueShared
 
 /* This is a copy of an AUTOSAR rule, which we are using for testing purposes. */
-/*
- * This query performs a simple syntactic check to ensure that the return value of the function is
- * not completely ignored. This matches the examples given in the rule, although the text itself is
- * not entirely clear. This means it will not find cases where something is done with the return
- * value, but it is not meaningfully read. For example: `int ret_val = f();`, with no subsequent
- * access of `ret_val`. However, such a case _would_ be flagged by A0-1-1 - Useless assignment.
- */
+module UnusedReturnValueConfig implements UnusedReturnValueSharedConfigSig {
+  Query getQuery() { result = DeadCodePackage::unusedReturnValueQuery() }
+}
 
-from FunctionCall fc, Function f
-where
-  not isExcluded(fc, DeadCodePackage::unusedReturnValueQuery()) and
-  // Find function calls in `ExprStmt`s, which indicate the return value is ignored
-  fc.getParent() instanceof ExprStmt and
-  // Ignore calls to void functions, which don't return values
-  not fc.getType() instanceof VoidType and
-  // Get the function target
-  f = fc.getTarget() and
-  // Overloaded (i.e. user defined) operators should behave in the same way as built-in operators,
-  // so the rule does not require the use of the return value
-  not f instanceof Operator and
-  // Exclude cases where the function call is generated within a macro, as the user of the macro is
-  // not necessarily able to address thoes results
-  not fc.isAffectedByMacro() and
-  // Rule allows disabling this rule where a static_cast<void> is applied
-  not fc.getExplicitlyConverted().(StaticCast).getActualType() instanceof VoidType
-select fc, "Return value from call to $@ is unused.", f, f.getName()
+import UnusedReturnValueShared<UnusedReturnValueConfig>
diff --git a/cpp/common/test/deviations/deviations_report_deviated/UnusedReturnValue.ql b/cpp/common/test/deviations/deviations_report_deviated/UnusedReturnValue.ql
@@ -17,31 +17,11 @@
 import cpp
 import codingstandards.cpp.CodingStandards
 import codingstandards.cpp.exclusions.cpp.RuleMetadata
+import codingstandards.cpp.rules.unusedreturnvalueshared.UnusedReturnValueShared
 
 /* This is a copy of an AUTOSAR rule, which we are using for testing purposes. */
-/*
- * This query performs a simple syntactic check to ensure that the return value of the function is
- * not completely ignored. This matches the examples given in the rule, although the text itself is
- * not entirely clear. This means it will not find cases where something is done with the return
- * value, but it is not meaningfully read. For example: `int ret_val = f();`, with no subsequent
- * access of `ret_val`. However, such a case _would_ be flagged by A0-1-1 - Useless assignment.
- */
+module UnusedReturnValueConfig implements UnusedReturnValueSharedConfigSig {
+  Query getQuery() { result = DeadCodePackage::unusedReturnValueQuery() }
+}
 
-from FunctionCall fc, Function f
-where
-  not isExcluded(fc, DeadCodePackage::unusedReturnValueQuery()) and
-  // Find function calls in `ExprStmt`s, which indicate the return value is ignored
-  fc.getParent() instanceof ExprStmt and
-  // Ignore calls to void functions, which don't return values
-  not fc.getType() instanceof VoidType and
-  // Get the function target
-  f = fc.getTarget() and
-  // Overloaded (i.e. user defined) operators should behave in the same way as built-in operators,
-  // so the rule does not require the use of the return value
-  not f instanceof Operator and
-  // Exclude cases where the function call is generated within a macro, as the user of the macro is
-  // not necessarily able to address thoes results
-  not fc.isAffectedByMacro() and
-  // Rule allows disabling this rule where a static_cast<void> is applied
-  not fc.getExplicitlyConverted().(StaticCast).getActualType() instanceof VoidType
-select fc, "Return value from call to $@ is unused.", f, f.getName()
+import UnusedReturnValueShared<UnusedReturnValueConfig>
diff --git a/cpp/common/test/rules/unusedreturnvalueshared/UnusedReturnValueShared.expected b/cpp/common/test/rules/unusedreturnvalueshared/UnusedReturnValueShared.expected
@@ -0,0 +1 @@
+| test.cpp:15:3:15:3 | call to f | Return value from call to $@ is unused. | test.cpp:3:5:3:5 | f | f |
diff --git a/cpp/common/test/rules/unusedreturnvalueshared/UnusedReturnValueShared.ql b/cpp/common/test/rules/unusedreturnvalueshared/UnusedReturnValueShared.ql
@@ -0,0 +1,8 @@
+// GENERATED FILE - DO NOT MODIFY
+import codingstandards.cpp.rules.unusedreturnvalueshared.UnusedReturnValueShared
+
+module TestFileConfig implements UnusedReturnValueSharedConfigSig {
+  Query getQuery() { result instanceof TestQuery }
+}
+
+import UnusedReturnValueShared<TestFileConfig>
diff --git a/cpp/common/test/rules/unusedreturnvalueshared/test.cpp b/cpp/common/test/rules/unusedreturnvalueshared/test.cpp
@@ -5,6 +5,9 @@ void g(int x);
 
 class A {
 public:
+  A() {
+    g(2); // Make constructor non-trivial so its call is always extracted.
+  }
   A operator+(const A &other);
 };
 
@@ -21,6 +24,7 @@ void test_return_val() {
   a1 + a2; // COMPLIANT - `+` is a call to operator+, but is permitted by the
            // rule
 
+  A a3{};    // COMPLIANT - not function call syntax.
   (void)f(); // COMPLIANT - explicitly ignoring the return value by C-style cast
              // to void.
   std::ignore = f(); // COMPLIANT - explicitly ignoring the return value by
diff --git a/cpp/misra/src/rules/RULE-0-1-2/UnusedReturnValueMisraCpp.ql b/cpp/misra/src/rules/RULE-0-1-2/UnusedReturnValueMisraCpp.ql
@@ -0,0 +1,23 @@
+/**
+ * @id cpp/misra/unused-return-value-misra-cpp
+ * @name RULE-0-1-2: The value returned by a function shall be used
+ * @description The result of a non-void function shall be used if called with function call syntax.
+ * @kind problem
+ * @precision very-high
+ * @problem.severity error
+ * @tags external/misra/id/rule-0-1-2
+ *       scope/single-translation-unit
+ *       correctness
+ *       external/misra/enforcement/decidable
+ *       external/misra/obligation/required
+ */
+
+import cpp
+import codingstandards.cpp.misra
+import codingstandards.cpp.rules.unusedreturnvalueshared.UnusedReturnValueShared
+
+module UnusedReturnValueMisraCppConfig implements UnusedReturnValueSharedConfigSig {
+  Query getQuery() { result = DeadCode6Package::unusedReturnValueMisraCppQuery() }
+}
+
+import UnusedReturnValueShared<UnusedReturnValueMisraCppConfig>
diff --git a/cpp/misra/test/rules/RULE-0-1-2/UnusedReturnValueMisraCpp.testref b/cpp/misra/test/rules/RULE-0-1-2/UnusedReturnValueMisraCpp.testref
@@ -0,0 +1 @@
+cpp/common/test/rules/unusedreturnvalueshared/UnusedReturnValueShared.ql
diff --git a/rule_packages/cpp/DeadCode.json b/rule_packages/cpp/DeadCode.json
@@ -40,6 +40,7 @@
           "precision": "very-high",
           "severity": "warning",
           "short_name": "UnusedReturnValue",
+          "shared_implementation_short_name": "UnusedReturnValueShared",
           "tags": [
             "readability",
             "maintainability"
diff --git a/rule_packages/cpp/DeadCode6.json b/rule_packages/cpp/DeadCode6.json
@@ -0,0 +1,26 @@
+{
+  "MISRA-C++-2023": {
+    "RULE-0-1-2": {
+      "properties": {
+        "enforcement": "decidable",
+        "obligation": "required"
+      },
+      "queries": [
+        {
+          "description": "The result of a non-void function shall be used if called with function call syntax.",
+          "kind": "problem",
+          "name": "The value returned by a function shall be used",
+          "precision": "very-high",
+          "severity": "error",
+          "short_name": "UnusedReturnValueMisraCpp",
+          "shared_implementation_short_name": "UnusedReturnValueShared",
+          "tags": [
+            "scope/single-translation-unit",
+            "correctness"
+          ]
+        }
+      ],
+      "title": "The value returned by a function shall be used"
+    }
+  }
+}
diff --git a/rules.csv b/rules.csv
@@ -826,7 +826,7 @@ c,MISRA-C-2012,RULE-23-8,Yes,Required,,,A default association shall appear as ei
 cpp,MISRA-C++-2023,RULE-0-0-1,Yes,Required,Decidable,Single Translation Unit,A function shall not contain unreachable statements,M0-1-1,DeadCode3,Medium,
 cpp,MISRA-C++-2023,RULE-0-0-2,Yes,Advisory,Undecidable,System,Controlling expressions should not be invariant,M0-1-2,DeadCode4,Easy,
 cpp,MISRA-C++-2023,RULE-0-1-1,Yes,Advisory,Undecidable,System,A value should not be unnecessarily written to a local object,A0-1-1,DeadCode2,Medium,
-cpp,MISRA-C++-2023,RULE-0-1-2,Yes,Required,Decidable,Single Translation Unit,The value returned by a function shall be used,A0-1-2,DeadCode2,Easy,
+cpp,MISRA-C++-2023,RULE-0-1-2,Yes,Required,Decidable,Single Translation Unit,The value returned by a function shall be used,A0-1-2,DeadCode6,Easy,
 cpp,MISRA-C++-2023,RULE-0-2-1,Yes,Advisory,Decidable,Single Translation Unit,Variables with limited visibility should be used at least once,M0-1-3,DeadCode2,Easy,
 cpp,MISRA-C++-2023,RULE-0-2-2,Yes,Required,Decidable,Single Translation Unit,A named function parameter shall be used at least once,"A0-1-4, A0-1-5",DeadCode2,Easy,
 cpp,MISRA-C++-2023,RULE-0-2-3,Yes,Advisory,Decidable,Single Translation Unit,Types with limited visibility should be used at least once,A0-1-6,DeadCode2,Easy,

Original file line number	Diff line number	Diff line change
`@@ -0,0 +1,2 @@`
	`1`	+ - `A0-1-2` - `UnusedReturnValue.ql`:
	`2`	`+ - Refactors the rule implementation into a shared library for usage in MISRA C++ ruleset. No externally visible changes expected.`
Original file line number	Diff line number	Diff line change
`@@ -0,0 +1 @@`
	`1`	`+cpp/common/test/rules/unusedreturnvalueshared/UnusedReturnValueShared.ql`