[clang-tidy][libc] Ignore implicit function inline (#71095)

This patch adjusts the inline function decl check for LLVM libc to
ignore implicit functions. For the moment the plan is to ignore these
and mark the class with a macro so that it can be given the appropriate
properties without explicitly defining all its ctors/dtors.

Author: michaelrj-google

clang-tools-extra/clang-tidy/llvmlibc/InlineFunctionDeclCheck.cpp

@@ -45,7 +45,9 @@ InlineFunctionDeclCheck::InlineFunctionDeclCheck(StringRef Name,
       HeaderFileExtensions(Context->getHeaderFileExtensions()) {}
 
 void InlineFunctionDeclCheck::registerMatchers(MatchFinder *Finder) {
-  Finder->addMatcher(decl(functionDecl()).bind("func_decl"), this);
+  // Ignore functions that have been deleted.
+  Finder->addMatcher(decl(functionDecl(unless(isDeleted()))).bind("func_decl"),
+                     this);
 }
 
 void InlineFunctionDeclCheck::check(const MatchFinder::MatchResult &Result) {

clang-tools-extra/clang-tidy/llvmlibc/InlineFunctionDeclCheck.h

@@ -33,6 +33,11 @@ class InlineFunctionDeclCheck : public ClangTidyCheck {
   void registerMatchers(ast_matchers::MatchFinder *Finder) override;
   void check(const ast_matchers::MatchFinder::MatchResult &Result) override;
 
+  // Ignore implicit functions (e.g. implicit constructors or destructors)
+  std::optional<TraversalKind> getCheckTraversalKind() const override {
+    return TK_IgnoreUnlessSpelledInSource;
+  }
+
 private:
   FileExtensionsSet HeaderFileExtensions;
 };

clang-tools-extra/docs/ReleaseNotes.rst

@@ -304,6 +304,10 @@ Changes in existing checks
   customizable namespace. This further allows for testing the libc when the
   system-libc is also LLVM's libc.
 
+- Improved :doc:`llvmlibc-inline-function-decl
+  <clang-tidy/checks/llvmlibc/inline-function-decl>` to properly ignore implicit
+  functions, such as struct constructors, and explicitly deleted functions.
+
 - Improved :doc:`misc-const-correctness
   <clang-tidy/checks/misc/const-correctness>` check to avoid false positive when
   using pointer to member function.

clang-tools-extra/docs/clang-tidy/checks/llvmlibc/inline-function-decl.rst

@@ -3,6 +3,8 @@
 llvmlibc-inline-function-decl
 =============================
 
-Checks that all implicit and explicit inline functions in header files are
-tagged with the ``LIBC_INLINE`` macro. See the `libc style guide
-<https://libc.llvm.org/dev/code_style.html>`_ for more information about this macro.
+Checks that all implicitly and explicitly inline functions in header files are
+tagged with the ``LIBC_INLINE`` macro, except for functions implicit to classes
+or deleted functions.
+See the `libc style guide <https://libc.llvm.org/dev/code_style.html>`_ for more
+information about this macro.

clang-tools-extra/test/clang-tidy/checkers/llvmlibc/inline-function-decl.hpp

@@ -278,6 +278,28 @@ template <typename T>LIBC_INLINE void goodWeirdFormatting() {}
 template <typename T>void LIBC_INLINE badWeirdFormatting() {}
 // CHECK-MESSAGES: :[[@LINE-1]]:22: warning: 'badWeirdFormatting' must be tagged with the LIBC_INLINE macro; the macro should be placed at the beginning of the declaration [llvmlibc-inline-function-decl]
 
+
+template <unsigned int NumberOfBits> struct HasMemberAndTemplate {
+  char Data[NumberOfBits];
+
+  void explicitFunction() {}
+// CHECK-MESSAGES: :[[@LINE-1]]:3: warning: 'explicitFunction' must be tagged with the LIBC_INLINE macro; the macro should be placed at the beginning of the declaration [llvmlibc-inline-function-decl]
+// CHECK-FIXES: LIBC_INLINE void explicitFunction() {}
+};
+
+static auto instanceOfStruct = HasMemberAndTemplate<16>(); 
+
+struct HasMemberAndExplicitDefault {
+  int TrivialMember;
+
+  HasMemberAndExplicitDefault() = default;
+// CHECK-MESSAGES: :[[@LINE-1]]:3: warning: 'HasMemberAndExplicitDefault' must be tagged with the LIBC_INLINE macro; the macro should be placed at the beginning of the declaration [llvmlibc-inline-function-decl]
+// CHECK-FIXES: LIBC_INLINE HasMemberAndExplicitDefault() = default;
+
+  ~HasMemberAndExplicitDefault() = delete;
+};
+
+
 } // namespace issue_62746
 
 } // namespace __llvm_libc