Fix a false positive in misc-redundant-expression check

Do not warn for redundant conditional expressions when the true and false
branches are expanded from different macros even when they are defined by
one another.

Patch by Daniel Krupp.

2 files changed, 78 insertions, 8 deletions

diff --git a/clang-tools-extra/clang-tidy/misc/RedundantExpressionCheck.cpp b/clang-tools-extra/clang-tidy/misc/RedundantExpressionCheck.cpp
index e646ee91ac5..e3e84b71601 100644
--- a/clang-tools-extra/clang-tidy/misc/RedundantExpressionCheck.cpp
+++ b/clang-tools-extra/clang-tidy/misc/RedundantExpressionCheck.cpp
@@ -131,6 +131,20 @@ static bool areEquivalentExpr(const Expr *Left, const Expr *Right) {
   case Stmt::BinaryOperatorClass:
     return cast<BinaryOperator>(Left)->getOpcode() ==
            cast<BinaryOperator>(Right)->getOpcode();
+  case Stmt::UnaryExprOrTypeTraitExprClass:
+    const auto *LeftUnaryExpr =
+        cast<UnaryExprOrTypeTraitExpr>(Left);
+    const auto *RightUnaryExpr =
+        cast<UnaryExprOrTypeTraitExpr>(Right);
+    if (LeftUnaryExpr->isArgumentType() && RightUnaryExpr->isArgumentType())
+      return LeftUnaryExpr->getArgumentType() ==
+             RightUnaryExpr->getArgumentType();
+    else if (!LeftUnaryExpr->isArgumentType() &&
+             !RightUnaryExpr->isArgumentType())
+      return areEquivalentExpr(LeftUnaryExpr->getArgumentExpr(),
+                               RightUnaryExpr->getArgumentExpr());
+
+    return false;
   }
 }
 
@@ -604,23 +618,62 @@ static bool retrieveConstExprFromBothSides(const BinaryOperator *&BinOp,
   return true;
 }
 
+static bool isSameRawIdentifierToken(const Token &T1, const Token &T2,
+                        const SourceManager &SM) {
+  if (T1.getKind() != T2.getKind())
+    return false;
+  if (T1.isNot(tok::raw_identifier))
+    return true;
+  if (T1.getLength() != T2.getLength())
+    return false;
+  return StringRef(SM.getCharacterData(T1.getLocation()), T1.getLength()) ==
+         StringRef(SM.getCharacterData(T2.getLocation()), T2.getLength());
+}
+
+bool isTokAtEndOfExpr(SourceRange ExprSR, Token T, const SourceManager &SM) {
+  return SM.getExpansionLoc(ExprSR.getEnd()) == T.getLocation();
+}
+
+/// Returns true if both LhsEpxr and RhsExpr are
+/// macro expressions and they are expanded
+/// from different macros.
 static bool areExprsFromDifferentMacros(const Expr *LhsExpr,
                                         const Expr *RhsExpr,
                                         const ASTContext *AstCtx) {
   if (!LhsExpr || !RhsExpr)
     return false;
-
-  SourceLocation LhsLoc = LhsExpr->getExprLoc();
-  SourceLocation RhsLoc = RhsExpr->getExprLoc();
-
-  if (!LhsLoc.isMacroID() || !RhsLoc.isMacroID())
+  SourceRange Lsr = LhsExpr->getSourceRange();
+  SourceRange Rsr = RhsExpr->getSourceRange();
+  if (!Lsr.getBegin().isMacroID() || !Rsr.getBegin().isMacroID())
     return false;
 
   const SourceManager &SM = AstCtx->getSourceManager();
   const LangOptions &LO = AstCtx->getLangOpts();
 
-  return !(Lexer::getImmediateMacroName(LhsLoc, SM, LO) ==
-          Lexer::getImmediateMacroName(RhsLoc, SM, LO));
+  std::pair<FileID, unsigned> LsrLocInfo =
+      SM.getDecomposedLoc(SM.getExpansionLoc(Lsr.getBegin()));
+  std::pair<FileID, unsigned> RsrLocInfo =
+      SM.getDecomposedLoc(SM.getExpansionLoc(Rsr.getBegin()));
+  const llvm::MemoryBuffer *MB = SM.getBuffer(LsrLocInfo.first);
+
+  const char *LTokenPos = MB->getBufferStart() + LsrLocInfo.second;
+  const char *RTokenPos = MB->getBufferStart() + RsrLocInfo.second;
+  Lexer LRawLex(SM.getLocForStartOfFile(LsrLocInfo.first), LO,
+                MB->getBufferStart(), LTokenPos, MB->getBufferEnd());
+  Lexer RRawLex(SM.getLocForStartOfFile(RsrLocInfo.first), LO,
+                MB->getBufferStart(), RTokenPos, MB->getBufferEnd());
+
+  Token LTok, RTok;
+  do { // Compare the expressions token-by-token.
+    LRawLex.LexFromRawLexer(LTok);
+    RRawLex.LexFromRawLexer(RTok);
+  } while (!LTok.is(tok::eof) && !RTok.is(tok::eof) &&
+           isSameRawIdentifierToken(LTok, RTok, SM) &&
+           !isTokAtEndOfExpr(Lsr, LTok, SM) &&
+           !isTokAtEndOfExpr(Rsr, RTok, SM));
+  return (!isTokAtEndOfExpr(Lsr, LTok, SM) ||
+          !isTokAtEndOfExpr(Rsr, RTok, SM)) ||
+         !isSameRawIdentifierToken(LTok, RTok, SM);
 }
 
 static bool areExprsMacroAndNonMacro(const Expr *&LhsExpr,
diff --git a/clang-tools-extra/test/clang-tidy/checkers/misc-redundant-expression.cpp b/clang-tools-extra/test/clang-tidy/checkers/misc-redundant-expression.cpp
index f6b47eb79fb..500478159a4 100644
--- a/clang-tools-extra/test/clang-tidy/checkers/misc-redundant-expression.cpp
+++ b/clang-tools-extra/test/clang-tidy/checkers/misc-redundant-expression.cpp
@@ -114,6 +114,7 @@ int Valid(int X, int Y) {
 
 #define COND_OP_MACRO 9
 #define COND_OP_OTHER_MACRO 9
+#define COND_OP_THIRD_MACRO COND_OP_MACRO
 int TestConditional(int x, int y) {
   int k = 0;
   k += (y < 0) ? x : x;
@@ -122,11 +123,27 @@ int TestConditional(int x, int y) {
   // CHECK-MESSAGES: :[[@LINE-1]]:24: warning: 'true' and 'false' expressions are equivalent
   k += (y < 0) ? COND_OP_MACRO : COND_OP_MACRO;
   // CHECK-MESSAGES: :[[@LINE-1]]:32: warning: 'true' and 'false' expressions are equivalent
+  k += (y < 0) ? COND_OP_MACRO + COND_OP_OTHER_MACRO : COND_OP_MACRO + COND_OP_OTHER_MACRO;
+  // CHECK-MESSAGES: :[[@LINE-1]]:54: warning: 'true' and 'false' expressions are equivalent
 
   // Do not match for conditional operators with a macro and a const.
   k += (y < 0) ? COND_OP_MACRO : 9;
   // Do not match for conditional operators with expressions from different macros.
   k += (y < 0) ? COND_OP_MACRO : COND_OP_OTHER_MACRO;
+  // Do not match for conditional operators when a macro is defined to another macro
+  k += (y < 0) ? COND_OP_MACRO : COND_OP_THIRD_MACRO;
+#undef COND_OP_THIRD_MACRO
+#define   COND_OP_THIRD_MACRO 8
+  k += (y < 0) ? COND_OP_MACRO : COND_OP_THIRD_MACRO;
+#undef COND_OP_THIRD_MACRO
+
+  k += (y < 0) ? sizeof(I64) : sizeof(I64);
+  // CHECK-MESSAGES: :[[@LINE-1]]:30: warning: 'true' and 'false' expressions are equivalent
+  k += (y < 0) ? sizeof(TestConditional(k,y)) : sizeof(TestConditional(k,y));
+  // CHECK-MESSAGES: :[[@LINE-1]]:47: warning: 'true' and 'false' expressions are equivalent
+  // No warning if the expression arguments are different.
+  k += (y < 0) ? sizeof(TestConditional(k,y)) : sizeof(Valid(k,y));
+
   return k;
 }
 #undef COND_OP_MACRO
@@ -134,7 +151,7 @@ int TestConditional(int x, int y) {
 
 // Overloaded operators that compare two instances of a struct.
 struct MyStruct {
-  int x;  
+  int x;
   bool operator==(const MyStruct& rhs) const {return this->x == rhs.x; } // not modifing
   bool operator>=(const MyStruct& rhs) const { return this->x >= rhs.x; } // not modifing
   bool operator<=(MyStruct& rhs) const { return this->x <= rhs.x; }