[clang-tidy] Make copy-and-swap idiom more general for bugprone-unhandled-self-assignment

clang-tools-extra/clang-tidy/bugprone/UnhandledSelfAssignmentCheck.cpp

@@ -69,6 +69,22 @@ void UnhandledSelfAssignmentCheck::registerMatchers(MatchFinder *Finder) {
       cxxMethodDecl(unless(hasDescendant(cxxMemberCallExpr(callee(cxxMethodDecl(
           hasName("operator="), ofClass(equalsBoundNode("class"))))))));
 
+  // Checking that some kind of constructor is called and followed by a `swap`:
+  // T& operator=(const T& other) {
+  //    T tmp{this->internal_data(), some, other, args};
+  //    swap(tmp);
+  //    return *this;
+  // }
+  const auto HasCopyAndSwap = cxxMethodDecl(
+      ofClass(cxxRecordDecl(unless(hasAncestor(classTemplateDecl())))),
+      hasDescendant(
+          stmt(hasDescendant(
+                   varDecl(hasType(cxxRecordDecl(equalsBoundNode("class"))))
+                       .bind("tmp_var")),
+               hasDescendant(callExpr(callee(functionDecl(hasName("swap"))),
+                                      hasAnyArgument(declRefExpr(to(varDecl(
+                                          equalsBoundNode("tmp_var"))))))))));
+
   DeclarationMatcher AdditionalMatcher = cxxMethodDecl();
   if (WarnOnlyIfThisHasSuspiciousField) {
     // Matcher for standard smart pointers.
@@ -89,14 +105,14 @@ void UnhandledSelfAssignmentCheck::registerMatchers(MatchFinder *Finder) {
                             hasType(arrayType())))))));
   }
 
-  Finder->addMatcher(cxxMethodDecl(ofClass(cxxRecordDecl().bind("class")),
-                                   isCopyAssignmentOperator(), IsUserDefined,
-                                   HasReferenceParam, HasNoSelfCheck,
-                                   unless(HasNonTemplateSelfCopy),
-                                   unless(HasTemplateSelfCopy),
-                                   HasNoNestedSelfAssign, AdditionalMatcher)
-                         .bind("copyAssignmentOperator"),
-                     this);
+  Finder->addMatcher(
+      cxxMethodDecl(
+          ofClass(cxxRecordDecl().bind("class")), isCopyAssignmentOperator(),
+          IsUserDefined, HasReferenceParam, HasNoSelfCheck,
+          unless(HasNonTemplateSelfCopy), unless(HasTemplateSelfCopy),
+          unless(HasCopyAndSwap), HasNoNestedSelfAssign, AdditionalMatcher)
+          .bind("copyAssignmentOperator"),
+      this);
 }
 
 void UnhandledSelfAssignmentCheck::check(

clang-tools-extra/docs/ReleaseNotes.rst

@@ -189,6 +189,12 @@ Changes in existing checks
   calls of ``std::string`` constructor with char pointer, start position and
   length parameters.
 
+- Improved :doc:`bugprone-unhandled-self-assignment
+  <clang-tidy/checks/bugprone/unhandled-self-assignment>` check by adding
+  an additional matcher that generalizes the copy-and-swap idiom pattern
+  detection. The checker now properly recognizes copy-and-swap implementations
+  that use "extended" copy/move constructors.
+
 - Improved :doc:`bugprone-unchecked-optional-access
   <clang-tidy/checks/bugprone/unchecked-optional-access>` fixing false
   positives from smart pointer accessors repeated in checking ``has_value``

clang-tools-extra/test/clang-tidy/checkers/bugprone/unhandled-self-assignment.cpp

@@ -28,6 +28,13 @@ template <class T>
 class auto_ptr {
 };
 
+namespace pmr {
+    template <typename TYPE = void>
+    class allocator {};
+}
+
+struct allocator_arg_t {} allocator_arg;
+
 } // namespace std
 
 void assert(int expression){};
@@ -540,6 +547,89 @@ class NotACopyAssignmentOperator {
   Uy *getUy() const { return Ptr2; }
 };
 
+// Support "extended" copy/move constructors
+class AllocatorAwareClass {
+  // pointer member to trigger bugprone-unhandled-self-assignment
+  void *foo = nullptr;
+
+  public:
+    using allocator_type = std::pmr::allocator<>;
+
+    AllocatorAwareClass(const AllocatorAwareClass& other) {
+    }
+
+    AllocatorAwareClass(const AllocatorAwareClass& other, const allocator_type& alloc) {
+    }
+
+    AllocatorAwareClass& operator=(const AllocatorAwareClass& other) {
+        AllocatorAwareClass tmp(other, get_allocator());
+        swap(tmp);
+        return *this;
+    }
+
+    void swap(AllocatorAwareClass& other) noexcept {
+    }
+
+    allocator_type get_allocator() const {
+        return allocator_type();
+    }
+};
+
+// Support "extended" copy/move constructors + std::swap
+class AllocatorAwareClassStdSwap {
+  // pointer member to trigger bugprone-unhandled-self-assignment
+  void *foo = nullptr;
+
+  public:
+    using allocator_type = std::pmr::allocator<>;
+
+    AllocatorAwareClassStdSwap(const AllocatorAwareClassStdSwap& other) {
+    }
+
+    AllocatorAwareClassStdSwap(const AllocatorAwareClassStdSwap& other, const allocator_type& alloc) {
+    }
+
+    AllocatorAwareClassStdSwap& operator=(const AllocatorAwareClassStdSwap& other) {
+        using std::swap;
+
+        AllocatorAwareClassStdSwap tmp(other, get_allocator());
+        swap(*this, tmp);
+        return *this;
+    }
+
+    allocator_type get_allocator() const {
+        return allocator_type();
+    }
+};
+
+// Support "extended" copy/move constructors + ADL swap
+class AllocatorAwareClassAdlSwap {
+  // pointer member to trigger bugprone-unhandled-self-assignment
+  void *foo = nullptr;
+
+  public:
+    using allocator_type = std::pmr::allocator<>;
+
+    AllocatorAwareClassAdlSwap(const AllocatorAwareClassAdlSwap& other) {
+    }
+
+    AllocatorAwareClassAdlSwap(const AllocatorAwareClassAdlSwap& other, const allocator_type& alloc) {
+    }
+
+    AllocatorAwareClassAdlSwap& operator=(const AllocatorAwareClassAdlSwap& other) {
+        AllocatorAwareClassAdlSwap tmp(other, get_allocator());
+        swap(*this, tmp);
+        return *this;
+    }
+
+    allocator_type get_allocator() const {
+        return allocator_type();
+    }
+
+    friend void swap(AllocatorAwareClassAdlSwap&, AllocatorAwareClassAdlSwap&) {
+    }
+};
+
 ///////////////////////////////////////////////////////////////////
 /// Test cases which should be caught by the check.