[clang-tidy] Add readability-avoid-default-lambda-capture

clang-tools-extra/clang-tidy/readability/DefaultLambdaCaptureCheck.cpp → clang-tools-extra/clang-tidy/readability/AvoidDefaultLambdaCaptureCheck.cpp

@@ -6,7 +6,7 @@
 //
 //===----------------------------------------------------------------------===//
 
-#include "DefaultLambdaCaptureCheck.h"
+#include "AvoidDefaultLambdaCaptureCheck.h"
 #include "clang/ASTMatchers/ASTMatchFinder.h"
 
 using namespace clang::ast_matchers;
@@ -20,11 +20,12 @@ AST_MATCHER(LambdaExpr, hasDefaultCapture) {
 
 } // namespace
 
-void DefaultLambdaCaptureCheck::registerMatchers(MatchFinder *Finder) {
+void AvoidDefaultLambdaCaptureCheck::registerMatchers(MatchFinder *Finder) {
   Finder->addMatcher(lambdaExpr(hasDefaultCapture()).bind("lambda"), this);
 }
 
-void DefaultLambdaCaptureCheck::check(const MatchFinder::MatchResult &Result) {
+void AvoidDefaultLambdaCaptureCheck::check(
+    const MatchFinder::MatchResult &Result) {
   const auto *Lambda = Result.Nodes.getNodeAs<LambdaExpr>("lambda");
   assert(Lambda);
 

clang-tools-extra/clang-tidy/readability/DefaultLambdaCaptureCheck.h → clang-tools-extra/clang-tidy/readability/AvoidDefaultLambdaCaptureCheck.h

@@ -6,21 +6,20 @@
 //
 //===----------------------------------------------------------------------===//
 
-#ifndef LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_READABILITY_DEFAULTLAMBDACAPTURECHECK_H
-#define LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_READABILITY_DEFAULTLAMBDACAPTURECHECK_H
+#ifndef LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_READABILITY_AVOIDDEFAULTLAMBDACAPTURECHECK_H
+#define LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_READABILITY_AVOIDDEFAULTLAMBDACAPTURECHECK_H
 
 #include "../ClangTidyCheck.h"
 
 namespace clang::tidy::readability {
 
-/** Flags lambdas that use default capture modes
- *
- * For the user-facing documentation see:
- * https://clang.llvm.org/extra/clang-tidy/checks/readability/default-lambda-capture.html
- */
-class DefaultLambdaCaptureCheck : public ClangTidyCheck {
+/// Flags lambdas that use default capture modes
+///
+/// For the user-facing documentation see:
+/// https://clang.llvm.org/extra/clang-tidy/checks/readability/avoid-default-lambda-capture.html
+class AvoidDefaultLambdaCaptureCheck : public ClangTidyCheck {
 public:
-  DefaultLambdaCaptureCheck(StringRef Name, ClangTidyContext *Context)
+  AvoidDefaultLambdaCaptureCheck(StringRef Name, ClangTidyContext *Context)
       : ClangTidyCheck(Name, Context) {}
   void registerMatchers(ast_matchers::MatchFinder *Finder) override;
   void check(const ast_matchers::MatchFinder::MatchResult &Result) override;
@@ -31,4 +30,4 @@ class DefaultLambdaCaptureCheck : public ClangTidyCheck {
 
 } // namespace clang::tidy::readability
 
-#endif // LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_READABILITY_DEFAULTLAMBDACAPTURECHECK_H
+#endif // LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_READABILITY_AVOIDDEFAULTLAMBDACAPTURECHECK_H

clang-tools-extra/clang-tidy/readability/CMakeLists.txt

@@ -6,6 +6,7 @@ set(LLVM_LINK_COMPONENTS
 add_clang_library(clangTidyReadabilityModule STATIC
   AmbiguousSmartptrResetCallCheck.cpp
   AvoidConstParamsInDecls.cpp
+  AvoidDefaultLambdaCaptureCheck.cpp
   AvoidNestedConditionalOperatorCheck.cpp
   AvoidReturnWithVoidValueCheck.cpp
   AvoidUnconditionalPreprocessorIfCheck.cpp
@@ -15,7 +16,6 @@ add_clang_library(clangTidyReadabilityModule STATIC
   ContainerDataPointerCheck.cpp
   ContainerSizeEmptyCheck.cpp
   ConvertMemberFunctionsToStatic.cpp
-  DefaultLambdaCaptureCheck.cpp
   DeleteNullPointerCheck.cpp
   DuplicateIncludeCheck.cpp
   ElseAfterReturnCheck.cpp

clang-tools-extra/clang-tidy/readability/ReadabilityTidyModule.cpp

@@ -11,6 +11,7 @@
 #include "../ClangTidyModuleRegistry.h"
 #include "AmbiguousSmartptrResetCallCheck.h"
 #include "AvoidConstParamsInDecls.h"
+#include "AvoidDefaultLambdaCaptureCheck.h"
 #include "AvoidNestedConditionalOperatorCheck.h"
 #include "AvoidReturnWithVoidValueCheck.h"
 #include "AvoidUnconditionalPreprocessorIfCheck.h"
@@ -20,7 +21,6 @@
 #include "ContainerDataPointerCheck.h"
 #include "ContainerSizeEmptyCheck.h"
 #include "ConvertMemberFunctionsToStatic.h"
-#include "DefaultLambdaCaptureCheck.h"
 #include "DeleteNullPointerCheck.h"
 #include "DuplicateIncludeCheck.h"
 #include "ElseAfterReturnCheck.h"
@@ -93,8 +93,8 @@ class ReadabilityModule : public ClangTidyModule {
         "readability-container-size-empty");
     CheckFactories.registerCheck<ConvertMemberFunctionsToStatic>(
         "readability-convert-member-functions-to-static");
-    CheckFactories.registerCheck<DefaultLambdaCaptureCheck>(
-        "readability-default-lambda-capture");
+    CheckFactories.registerCheck<AvoidDefaultLambdaCaptureCheck>(
+        "readability-avoid-default-lambda-capture");
     CheckFactories.registerCheck<DeleteNullPointerCheck>(
         "readability-delete-null-pointer");
     CheckFactories.registerCheck<DuplicateIncludeCheck>(

clang-tools-extra/docs/ReleaseNotes.rst

@@ -351,8 +351,8 @@ Changes in existing checks
   <clang-tidy/checks/readability/uppercase-literal-suffix>` check to recognize
   literal suffixes added in C++23 and C23.
 
-- New :doc:`readability-default-lambda-capture
-  <clang-tidy/checks/readability/default-lambda-capture>` check.
+- New :doc:`readability-avoid-default-lambda-capture
+  <clang-tidy/checks/readability/avoid-default-lambda-capture>` check.
 
   Warns on default lambda captures (e.g. ``[&](){ ... }``, ``[=](){ ... }``)
 

clang-tools-extra/docs/clang-tidy/checks/list.rst

@@ -377,7 +377,7 @@ Clang-Tidy Checks
    :doc:`readability-container-data-pointer <readability/container-data-pointer>`, "Yes"
    :doc:`readability-container-size-empty <readability/container-size-empty>`, "Yes"
    :doc:`readability-convert-member-functions-to-static <readability/convert-member-functions-to-static>`, "Yes"
-   :doc:`readability-default-lambda-capture <readability/default-lambda-capture>`,
+   :doc:`readability-avoid-default-lambda-capture <readability/avoid-default-lambda-capture>`,
    :doc:`readability-delete-null-pointer <readability/delete-null-pointer>`, "Yes"
    :doc:`readability-duplicate-include <readability/duplicate-include>`, "Yes"
    :doc:`readability-else-after-return <readability/else-after-return>`, "Yes"

clang-tools-extra/docs/clang-tidy/checks/readability/avoid-default-lambda-capture.rst

@@ -0,0 +1,55 @@
+.. title:: clang-tidy - readability-avoid-default-lambda-capture
+
+readability-avoid-default-lambda-capture
+=========================================
+
+Warns on default lambda captures (e.g. ``[&](){ ... }``, ``[=](){ ... }``)
+
+Captures can lead to subtle bugs including dangling references and unnecessary
+copies. Writing out the name of the variables being captured reminds programmers
+and reviewers to know what is being captured. And knowing is half the battle.
+
+Coding guidelines that recommend against defaulted lambda captures include:
+
+* Item 31 of Effective Modern C++ by Scott Meyers
+* `AUTOSAR C++ Rule A5-1-2 <https://www.mathworks.com/help//releases/
+  R2021a/bugfinder/ref/autosarc14rulea512.html>`__
+
+Example
+-------
+
+.. code-block:: c++
+
+  #include <iostream>
+
+  class Widget {
+    std::vector<std::function<void(int)>> callbacks;
+    int                                   widgetId;
+    void addCallback(int factoryId) {
+      callbacks.emplace_back(
+        [&](){
+          std::cout << "Widget " << widgetId << " made in factory " << factoryId;
+        }
+      );
+    }
+  }
+
+When ``callbacks`` is executed, ``factoryId`` will dangle. Writing the name of
+``factoryId`` in the capture list makes it easy to review the captures and
+detect obvious bugs.
+
+.. code-block:: c++
+
+  #include <iostream>
+
+  class Widget {
+    std::vector<std::function<void(int)>> callbacks;
+    int                                   widgetId;
+    void addCallback(int factoryId) {
+      callbacks.emplace_back(
+        [&factoryId, &widgetId](){ // Why isn't factoryId captured by value??
+          std::cout << "Widget " << widgetId << " made in factory " << factoryId;
+        }
+      );
+    }
+  }

clang-tools-extra/test/clang-tidy/checkers/readability/default-lambda-capture.cpp → clang-tools-extra/test/clang-tidy/checkers/readability/avoid-default-lambda-capture.cpp

@@ -1,20 +1,20 @@
-// RUN: %check_clang_tidy %s readability-default-lambda-capture %t
+// RUN: %check_clang_tidy %s readability-avoid-default-lambda-capture %t
 
 void test_default_captures() {
   int value = 42;
   int another = 10;
 
   auto lambda1 = [=](int x) { return value + x; };
-  // CHECK-MESSAGES: :[[@LINE-1]]:19: warning: lambda default captures are discouraged; prefer to capture specific variables explicitly [readability-default-lambda-capture]
+  // CHECK-MESSAGES: :[[@LINE-1]]:19: warning: lambda default captures are discouraged; prefer to capture specific variables explicitly [readability-avoid-default-lambda-capture]
 
   auto lambda2 = [&](int x) { return value + x; };
-  // CHECK-MESSAGES: :[[@LINE-1]]:19: warning: lambda default captures are discouraged; prefer to capture specific variables explicitly [readability-default-lambda-capture]
+  // CHECK-MESSAGES: :[[@LINE-1]]:19: warning: lambda default captures are discouraged; prefer to capture specific variables explicitly [readability-avoid-default-lambda-capture]
 
   auto lambda3 = [=, &another](int x) { return value + another + x; };
-  // CHECK-MESSAGES: :[[@LINE-1]]:19: warning: lambda default captures are discouraged; prefer to capture specific variables explicitly [readability-default-lambda-capture]
+  // CHECK-MESSAGES: :[[@LINE-1]]:19: warning: lambda default captures are discouraged; prefer to capture specific variables explicitly [readability-avoid-default-lambda-capture]
 
   auto lambda4 = [&, value](int x) { return value + another + x; };
-  // CHECK-MESSAGES: :[[@LINE-1]]:19: warning: lambda default captures are discouraged; prefer to capture specific variables explicitly [readability-default-lambda-capture]
+  // CHECK-MESSAGES: :[[@LINE-1]]:19: warning: lambda default captures are discouraged; prefer to capture specific variables explicitly [readability-avoid-default-lambda-capture]
 }
 
 void test_acceptable_captures() {
@@ -42,10 +42,10 @@ void test_nested_lambdas() {
   int inner_var = 3;
 
   auto outer = [=]() {
-    // CHECK-MESSAGES: :[[@LINE-1]]:17: warning: lambda default captures are discouraged; prefer to capture specific variables explicitly [readability-default-lambda-capture]
-    
+    // CHECK-MESSAGES: :[[@LINE-1]]:17: warning: lambda default captures are discouraged; prefer to capture specific variables explicitly [readability-avoid-default-lambda-capture]
+
     auto inner = [&](int x) { return outer_var + middle_var + inner_var + x; };
-    // CHECK-MESSAGES: :[[@LINE-1]]:19: warning: lambda default captures are discouraged; prefer to capture specific variables explicitly [readability-default-lambda-capture]
+    // CHECK-MESSAGES: :[[@LINE-1]]:19: warning: lambda default captures are discouraged; prefer to capture specific variables explicitly [readability-avoid-default-lambda-capture]
 
     return inner(10);
   };
@@ -55,15 +55,15 @@ void test_lambda_returns() {
   int a = 1, b = 2, c = 3;
 
   auto create_adder = [=](int x) {
-    // CHECK-MESSAGES: :[[@LINE-1]]:24: warning: lambda default captures are discouraged; prefer to capture specific variables explicitly [readability-default-lambda-capture]
+    // CHECK-MESSAGES: :[[@LINE-1]]:24: warning: lambda default captures are discouraged; prefer to capture specific variables explicitly [readability-avoid-default-lambda-capture]
     return [x](int y) { return x + y; }; // Inner lambda is fine - explicit capture
   };
 
   auto func1 = [&]() { return a; };
-  // CHECK-MESSAGES: :[[@LINE-1]]:17: warning: lambda default captures are discouraged; prefer to capture specific variables explicitly [readability-default-lambda-capture]
-  
+  // CHECK-MESSAGES: :[[@LINE-1]]:17: warning: lambda default captures are discouraged; prefer to capture specific variables explicitly [readability-avoid-default-lambda-capture]
+
   auto func2 = [=]() { return b; };
-  // CHECK-MESSAGES: :[[@LINE-1]]:17: warning: lambda default captures are discouraged; prefer to capture specific variables explicitly [readability-default-lambda-capture]
+  // CHECK-MESSAGES: :[[@LINE-1]]:17: warning: lambda default captures are discouraged; prefer to capture specific variables explicitly [readability-avoid-default-lambda-capture]
 }
 
 class TestClass {
@@ -74,10 +74,10 @@ class TestClass {
     int local = 10;
 
     auto lambda1 = [=]() { return member + local; };
-    // CHECK-MESSAGES: :[[@LINE-1]]:21: warning: lambda default captures are discouraged; prefer to capture specific variables explicitly [readability-default-lambda-capture]
-    
+    // CHECK-MESSAGES: :[[@LINE-1]]:21: warning: lambda default captures are discouraged; prefer to capture specific variables explicitly [readability-avoid-default-lambda-capture]
+
     auto lambda2 = [&]() { return member + local; };
-    // CHECK-MESSAGES: :[[@LINE-1]]:21: warning: lambda default captures are discouraged; prefer to capture specific variables explicitly [readability-default-lambda-capture]
+    // CHECK-MESSAGES: :[[@LINE-1]]:21: warning: lambda default captures are discouraged; prefer to capture specific variables explicitly [readability-avoid-default-lambda-capture]
 
     auto lambda3 = [this, local]() { return member + local; };
     auto lambda4 = [this, &local]() { return member + local; };
@@ -89,7 +89,7 @@ void test_template_lambdas() {
   T value{};
 
   auto lambda = [=](T x) { return value + x; };
-  // CHECK-MESSAGES: :[[@LINE-1]]:18: warning: lambda default captures are discouraged; prefer to capture specific variables explicitly [readability-default-lambda-capture]
+  // CHECK-MESSAGES: :[[@LINE-1]]:18: warning: lambda default captures are discouraged; prefer to capture specific variables explicitly [readability-avoid-default-lambda-capture]
 }
 
 void instantiate_templates() {