[clang-tidy] Don't issue most google-readability-casting warnings on .c files included in other files.

This is done sometimes for testing purposes, and the check needs to handle this
consistently.

llvm-svn: 238193

clang-tools-extra/clang-tidy/google/AvoidCStyleCastsCheck.cpp

@@ -97,15 +97,19 @@ void AvoidCStyleCastsCheck::check(const MatchFinder::MatchResult &Result) {
   // compiled as C++.
   if (getCurrentMainFile().endswith(".c"))
     return;
-
+  // Ignore code in .c files #included in other files (which shouldn't be done,
+  // but people still do this for test and other purposes).
+  SourceManager &SM = *Result.SourceManager;
+  if (SM.getFilename(SM.getSpellingLoc(CastExpr->getLocStart())).endswith(".c"))
+    return;
 
   // Leave type spelling exactly as it was (unlike
   // getTypeAsWritten().getAsString() which would spell enum types 'enum X').
-  StringRef DestTypeString = Lexer::getSourceText(
-      CharSourceRange::getTokenRange(
-          CastExpr->getLParenLoc().getLocWithOffset(1),
-          CastExpr->getRParenLoc().getLocWithOffset(-1)),
-      *Result.SourceManager, Result.Context->getLangOpts());
+  StringRef DestTypeString =
+      Lexer::getSourceText(CharSourceRange::getTokenRange(
+                               CastExpr->getLParenLoc().getLocWithOffset(1),
+                               CastExpr->getRParenLoc().getLocWithOffset(-1)),
+                           SM, Result.Context->getLangOpts());
 
   auto diag_builder =
       diag(CastExpr->getLocStart(), "C-style casts are discouraged. %0");
@@ -118,8 +122,7 @@ void AvoidCStyleCastsCheck::check(const MatchFinder::MatchResult &Result) {
     if (!isa<ParenExpr>(SubExpr)) {
       CastText.push_back('(');
       diag_builder << FixItHint::CreateInsertion(
-          Lexer::getLocForEndOfToken(SubExpr->getLocEnd(), 0,
-                                     *Result.SourceManager,
+          Lexer::getLocForEndOfToken(SubExpr->getLocEnd(), 0, SM,
                                      Result.Context->getLangOpts()),
           ")");
     }

clang-tools-extra/test/clang-tidy/google-readability-casting.c

@@ -2,11 +2,22 @@
 // The testing script always adds .cpp extension to the input file name, so we
 // need to run clang-tidy directly in order to verify handling of .c files:
 // RUN: clang-tidy --checks=-*,google-readability-casting %s -- -x c++ | FileCheck %s -check-prefix=CHECK-MESSAGES -implicit-check-not='{{warning|error}}:'
+// RUN: cp %s %t.main_file.cpp
+// RUN: clang-tidy --checks=-*,google-readability-casting -header-filter='.*' %t.main_file.cpp -- -I%S -DTEST_INCLUDE -x c++ | FileCheck %s -check-prefix=CHECK-MESSAGES -implicit-check-not='{{warning|error}}:'
 // REQUIRES: shell
 
+#ifdef TEST_INCLUDE
+
+#undef TEST_INCLUDE
+#include "google-readability-casting.c"
+
+#else
+
 void f(const char *cpc) {
   const char *cpc2 = (const char*)cpc;
   // CHECK-MESSAGES: :[[@LINE-1]]:22: warning: redundant cast to the same type [google-readability-casting]
   // CHECK-FIXES: const char *cpc2 = cpc;
   char *pc = (char*)cpc;
 }
+
+#endif