[clang-tidy] Do not lint on attribute macros

cppcoreguidelines-macro-usage lint incorrectly identifies these macros
as candidates for rewrite into template arguments.
There are no, variadic or not, equivalent to these macros using
templated functions.

Signed-off-by: Xiangfei Ding <[email protected]>

Author: dingxiangfei2009

clang-tools-extra/clang-tidy/cppcoreguidelines/MacroUsageCheck.cpp

@@ -82,17 +82,26 @@ void MacroUsageCheck::registerPPCallbacks(const SourceManager &SM,
 void MacroUsageCheck::warnMacro(const MacroDirective *MD, StringRef MacroName) {
   const MacroInfo *Info = MD->getMacroInfo();
   StringRef Message;
+  bool MacroBodyExpressionLike;
+  if (Info->getNumTokens() > 0) {
+    const Token &Tok = Info->getReplacementToken(0);
+    // Now notice that keywords like `__attribute` cannot be a leading
+    // token in an expression.
+    MacroBodyExpressionLike = !Tok.is(tok::kw___attribute);
+  } else {
+    MacroBodyExpressionLike = true;
+  }
 
   if (llvm::all_of(Info->tokens(), std::mem_fn(&Token::isLiteral)))
     Message = "macro '%0' used to declare a constant; consider using a "
               "'constexpr' constant";
   // A variadic macro is function-like at the same time. Therefore variadic
   // macros are checked first and will be excluded for the function-like
   // diagnostic.
-  else if (Info->isVariadic())
+  else if (Info->isVariadic() && MacroBodyExpressionLike)
     Message = "variadic macro '%0' used; consider using a 'constexpr' "
               "variadic template function";
-  else if (Info->isFunctionLike())
+  else if (Info->isFunctionLike() && MacroBodyExpressionLike)
     Message = "function-like macro '%0' used; consider a 'constexpr' template "
               "function";
 

clang-tools-extra/docs/ReleaseNotes.rst

@@ -325,6 +325,12 @@ Changes in existing checks
   <clang-tidy/checks/cppcoreguidelines/init-variables>` check by fixing the
   insertion location for function pointers with multiple parameters.
 
+- Improved :doc:`cppcoreguidelines-macro-usage
+  <clang-tidy/checks/cppcoreguidelines/macro-usage>` check by excluding macro
+  bodies that starts with ``__attribute__((..))`` keyword.
+  Such a macro body is unlikely a proper expression and so suggesting users
+  an impossible rewrite into a template function should be avoided.
+
 - Improved :doc:`cppcoreguidelines-prefer-member-initializer
   <clang-tidy/checks/cppcoreguidelines/prefer-member-initializer>` check to
   avoid false positives on inherited members in class templates.

clang-tools-extra/test/clang-tidy/checkers/cppcoreguidelines/macro-usage.cpp

@@ -47,4 +47,6 @@
 #define DLLEXPORTS __declspec(dllimport)
 #endif
 
+#define ATTRIBUTE_MACRO(...) __attribute__(__VA_ARGS__)
+
 #endif