Fix false positives in RULE-15-1-4 for class template constructors

change_notes/2026-10-20-fix-fp-rule-15-1-4-template-constructors.md

@@ -0,0 +1,2 @@
+- `RULE-15-1-4` - `NonStaticMemberNotInitBeforeUse.ql`:
+  - Remove false positives for constructors of uninstantiated class templates, where delegating constructors are not modelled as such. The instantiations are still checked.

cpp/misra/src/rules/RULE-15-1-4/NonStaticMemberNotInitBeforeUse.ql

@@ -116,6 +116,9 @@ class IncompleteConstructor extends Constructor, IncompleteInitialization {
     not getDeclaringType() instanceof Union and
     this.getDeclaringType().hasDefinition() and
     not this.isDeleted() and
+    // Constructors of uninstantiated class templates cannot be analysed reliably, because for
+    // instance a delegating constructor is not modelled as such. The instantiations are checked.
+    not this.getDeclaringType() instanceof TemplateClass and
     // Delegating constructors do not need to initialize members
     not any(ConstructorDelegationInit init) = this.getAnInitializer() and
     // exclude defaulted move and copy constructors.

cpp/misra/test/rules/RULE-15-1-4/NonStaticMemberNotInitBeforeUse.expected

@@ -24,3 +24,4 @@
 | test.cpp:267:18:267:18 | a | Aggregate variable does not initialize non-static data member $@ (and 9 more). | test.cpp:262:43:262:45 | m10 | m10 |
 | test.cpp:290:18:290:18 | a | Aggregate variable does not initialize non-static data member $@ (and 1 more). | test.cpp:285:9:285:10 | m1 | m1 |
 | test.cpp:290:18:290:18 | a | Aggregate variable does not initialize non-static data member $@ (and 1 more). | test.cpp:286:11:286:12 | m2 | m2 |
+| test.cpp:318:3:318:3 | TemplateMemberUninit | Constructor does not initialize non-static data member $@. | test.cpp:322:7:322:8 | m2 | m2 |

cpp/misra/test/rules/RULE-15-1-4/test.cpp

@@ -302,4 +302,52 @@ union UnionWithConstructor {
   // Union constructors should still be required to initialize one member, but
   // this is not implemented.
   UnionWithConstructor() {} // NON_COMPLIANT[False negative]
-};
+};
+template <typename T> class TemplateAllInit {
+public:
+  TemplateAllInit(T value) : m1(value), m2(0) {} // COMPLIANT
+  TemplateAllInit(const TemplateAllInit &) = delete;
+
+private:
+  T m1;
+  int m2;
+};
+
+template <typename T> class TemplateMemberUninit {
+public:
+  TemplateMemberUninit(T value) : m1(value) {} // NON_COMPLIANT
+
+private:
+  T m1;
+  int m2;
+};
+
+template <typename T> class TemplateOutOfLineInit {
+public:
+  TemplateOutOfLineInit(T value);
+
+private:
+  T m1;
+  int m2;
+};
+
+template <typename T>
+TemplateOutOfLineInit<T>::TemplateOutOfLineInit(T value)
+    : m1(value), m2(0) {} // COMPLIANT
+
+template <typename T> class TemplateDelegating {
+public:
+  TemplateDelegating() : TemplateDelegating(0) {}   // COMPLIANT
+  TemplateDelegating(T value) : m1(value), m2(0) {} // COMPLIANT
+
+private:
+  T m1;
+  int m2;
+};
+
+void instantiateTemplates() {
+  TemplateAllInit<int> a(1);
+  TemplateMemberUninit<int> b(1);
+  TemplateOutOfLineInit<int> c(1);
+  TemplateDelegating<int> d;
+}