Add AllowFalseEvaluated to clang-tidy noexcept-move-constructor check

Author: Nechda

clang-tools-extra/clang-tidy/performance/NoexceptFunctionBaseCheck.cpp

@@ -30,7 +30,7 @@ void NoexceptFunctionBaseCheck::check(const MatchFinder::MatchResult &Result) {
  const Expr *NoexceptExpr = ProtoType->getNoexceptExpr();
  if (NoexceptExpr) {
  NoexceptExpr = NoexceptExpr->IgnoreImplicit();
- if (!isa<CXXBoolLiteralExpr>(NoexceptExpr))
+ if (!isa<CXXBoolLiteralExpr>(NoexceptExpr) && !AllowFalseEvaluated)
  reportNoexceptEvaluatedToFalse(FuncDecl, NoexceptExpr);
  return;
  }

clang-tools-extra/clang-tidy/performance/NoexceptFunctionBaseCheck.h

@@ -22,7 +22,8 @@ namespace clang::tidy::performance {
 class NoexceptFunctionBaseCheck : public ClangTidyCheck {
 public:
  NoexceptFunctionBaseCheck(StringRef Name, ClangTidyContext *Context)
- : ClangTidyCheck(Name, Context) {}
+ : ClangTidyCheck(Name, Context)
+ , AllowFalseEvaluated(Options.getLocalOrGlobal("AllowFalseEvaluated", false)) {}
 
  bool isLanguageVersionSupported(const LangOptions &LangOpts) const override {
  return LangOpts.CPlusPlus11 && LangOpts.CXXExceptions;
@@ -33,6 +34,10 @@ class NoexceptFunctionBaseCheck : public ClangTidyCheck {
  return TK_IgnoreUnlessSpelledInSource;
  }
 
+ void storeOptions(ClangTidyOptions::OptionMap &Opts) override {
+ Options.store(Opts, "AllowFalseEvaluated", AllowFalseEvaluated);
+ }
+
 protected:
  virtual DiagnosticBuilder
  reportMissingNoexcept(const FunctionDecl *FuncDecl) = 0;
@@ -42,6 +47,7 @@ class NoexceptFunctionBaseCheck : public ClangTidyCheck {
  static constexpr StringRef BindFuncDeclName = "FuncDecl";
 
 private:
+ bool AllowFalseEvaluated;
  utils::ExceptionSpecAnalyzer SpecAnalyzer;
 };
 

clang-tools-extra/docs/ReleaseNotes.rst

@@ -110,6 +110,12 @@ Changes in existing checks
  <clang-tidy/checks/misc/redundant-expression>` check by providing additional
  examples and fixing some macro related false positives.
 
+- Improved :doc:`performance-noexcept-move-constructor
+ <clang-tidy/checks/performance/noexcept-move-constructor>` check by adding
+ a new (off-by-default) option `AllowFalseEvaluated`, which allows marking
+ move constructors with ``noexcept(expr)`` even if ``expr``
+ evaluates to ``false``.
+
 Removed checks
 ^^^^^^^^^^^^^^
 

clang-tools-extra/docs/clang-tidy/checks/performance/noexcept-move-constructor.rst

@@ -11,3 +11,12 @@ evaluates to ``false`` (but is not a ``false`` literal itself).
 Move constructors of all the types used with STL containers, for example,
 need to be declared ``noexcept``. Otherwise STL will choose copy constructors
 instead. The same is valid for move assignment operations.
+
+Options
+-------
+
+.. option:: AllowFalseEvaluated
+
+ When `true`, the check will not generate any warning
+ if the ``expr`` in ``noexcept(expr)`` evaluates to ``false``.
+ Default is `false`.

clang-tools-extra/test/clang-tidy/checkers/performance/noexcept-move-constructor-allow-false-evaluated.cpp

@@ -0,0 +1,63 @@
+// RUN: %check_clang_tidy %s performance-noexcept-move-constructor %t -- -- -fexceptions
+
+// RUN: %check_clang_tidy -check-suffix=CONFIG %s performance-noexcept-move-constructor,performance-noexcept-destructor %t -- \
+// RUN: -config="{CheckOptions: {performance-noexcept-move-constructor.AllowFalseEvaluated: true}}" \
+// RUN: -- -fexceptions
+
+namespace std
+{
+ template <typename T>
+ struct is_nothrow_move_constructible
+ {
+ static constexpr bool value = __is_nothrow_constructible(T, __add_rvalue_reference(T));
+ };
+} // namespace std
+
+struct ThrowOnAnything {
+ ThrowOnAnything() noexcept(false);
+ ThrowOnAnything(ThrowOnAnything&&) noexcept(false);
+ // CHECK-MESSAGES-NOT: :[[@LINE-1]]:3: warning: move constructors should be marked noexcept
+ // CHECK-MESSAGES-CONFIG-NOT: :[[@LINE-2]]:3: warning: move constructors should be marked noexcept
+ ThrowOnAnything& operator=(ThrowOnAnything &&) noexcept(false);
+ ~ThrowOnAnything() noexcept(false);
+};
+
+struct C_1 {
+ static constexpr bool kFalse = false;
+ C_1(C_1&&) noexcept(kFalse) = default;
+ // CHECK-MESSAGES: :[[@LINE-1]]:25: warning: noexcept specifier on the move constructor evaluates to 'false' [performance-noexcept-move-constructor]
+ // CHECK-MESSAGES-CONFIG-NOT: :[[@LINE-2]]:25: warning: noexcept specifier on the move constructor evaluates to 'false' [performance-noexcept-move-constructor]
+
+ C_1 &operator=(C_1 &&) noexcept(kFalse);
+ // CHECK-MESSAGES: :[[@LINE-1]]:37: warning: noexcept specifier on the move assignment operator evaluates to 'false' [performance-noexcept-move-constructor]
+ // CHECK-MESSAGES-CONFIG-NOT: :[[@LINE-2]]:37: warning: noexcept specifier on the move assignment operator evaluates to 'false' [performance-noexcept-move-constructor]
+};
+
+struct C_2 {
+ static constexpr bool kEval = std::is_nothrow_move_constructible<ThrowOnAnything>::value;
+ static_assert(!kEval); // kEval == false;
+
+ C_2(C_2&&) noexcept(kEval) = default;
+ // CHECK-MESSAGES: :[[@LINE-1]]:25: warning: noexcept specifier on the move constructor evaluates to 'false' [performance-noexcept-move-constructor]
+ // CHECK-MESSAGES-CONFIG-NOT: :[[@LINE-2]]:25: warning: noexcept specifier on the move constructor evaluates to 'false' [performance-noexcept-move-constructor]
+
+ C_2 &operator=(C_2 &&) noexcept(kEval);
+ // CHECK-MESSAGES: :[[@LINE-1]]:37: warning: noexcept specifier on the move assignment operator evaluates to 'false' [performance-noexcept-move-constructor]
+ // CHECK-MESSAGES-CONFIG-NOT: :[[@LINE-2]]:37: warning: noexcept specifier on the move assignment operator evaluates to 'false' [performance-noexcept-move-constructor]
+
+ ThrowOnAnything field;
+};
+
+struct C_3 {
+ static constexpr bool kEval = std::is_nothrow_move_constructible<ThrowOnAnything>::value;
+ static_assert(!kEval); // kEval == false;
+
+ C_3(C_3&&) noexcept(kEval) = default;
+ // CHECK-MESSAGES: :[[@LINE-1]]:25: warning: noexcept specifier on the move constructor evaluates to 'false' [performance-noexcept-move-constructor]
+ // CHECK-MESSAGES-CONFIG-NOT: :[[@LINE-2]]:25: warning: noexcept specifier on the move constructor evaluates to 'false' [performance-noexcept-move-constructor]
+
+ ~C_3() noexcept(kEval) = default;
+ // CHECK-MESSAGES-CONFIG: :[[@LINE-1]]:21: warning: noexcept specifier on the destructor evaluates to 'false'
+
+ ThrowOnAnything field;
+};