1 files changed, 48 insertions, 3 deletions

diff --git a/clang/lib/Sema/SemaExpr.cpp b/clang/lib/Sema/SemaExpr.cpp
index 1bab239ab32..ab96f7416fe 100644
--- a/clang/lib/Sema/SemaExpr.cpp
+++ b/clang/lib/Sema/SemaExpr.cpp
@@ -5948,6 +5948,46 @@ static bool checkArithmethicPointerOnNonFragileABI(Sema &S,
   return false;
 }
 
+/// diagnoseStringPlusInt - Emit a warning when adding an integer to a string
+/// literal.
+static void diagnoseStringPlusInt(Sema &Self, SourceLocation OpLoc,
+                                  Expr *LHSExpr, Expr *RHSExpr) {
+  StringLiteral* StrExpr = dyn_cast<StringLiteral>(LHSExpr->IgnoreImpCasts());
+  Expr* IndexExpr = RHSExpr;
+  if (!StrExpr) {
+    StrExpr = dyn_cast<StringLiteral>(RHSExpr->IgnoreImpCasts());
+    IndexExpr = LHSExpr;
+  }
+
+  bool IsStringPlusInt = StrExpr &&
+      IndexExpr->getType()->isIntegralOrUnscopedEnumerationType();
+  if (!IsStringPlusInt)
+    return;
+
+  llvm::APSInt index;
+  if (IndexExpr->EvaluateAsInt(index, Self.getASTContext())) {
+    unsigned StrLenWithNull = StrExpr->getLength() + 1;
+    if (index.isNonNegative() &&
+        index <= llvm::APSInt(llvm::APInt(index.getBitWidth(), StrLenWithNull),
+                              index.isUnsigned()))
+      return;
+  }
+
+  SourceRange DiagRange(LHSExpr->getLocStart(), RHSExpr->getLocEnd());
+  Self.Diag(OpLoc, diag::warn_string_plus_int)
+      << DiagRange << IndexExpr->IgnoreImpCasts()->getType();
+
+  // Only print a fixit for "str" + int, not for int + "str".
+  if (IndexExpr == RHSExpr) {
+    SourceLocation EndLoc = Self.PP.getLocForEndOfToken(RHSExpr->getLocEnd());
+    Self.Diag(OpLoc, diag::note_string_plus_int_silence)
+        << FixItHint::CreateInsertion(LHSExpr->getLocStart(), "&")
+        << FixItHint::CreateReplacement(SourceRange(OpLoc), "[")
+        << FixItHint::CreateInsertion(EndLoc, "]");
+  } else
+    Self.Diag(OpLoc, diag::note_string_plus_int_silence);
+}
+
 /// \brief Emit error when two pointers are incompatible.
 static void diagnosePointerIncompatibility(Sema &S, SourceLocation Loc,
                                            Expr *LHSExpr, Expr *RHSExpr) {
@@ -5959,7 +5999,8 @@ static void diagnosePointerIncompatibility(Sema &S, SourceLocation Loc,
 }
 
 QualType Sema::CheckAdditionOperands( // C99 6.5.6
-  ExprResult &LHS, ExprResult &RHS, SourceLocation Loc, QualType* CompLHSTy) {
+    ExprResult &LHS, ExprResult &RHS, SourceLocation Loc, unsigned Opc,
+    QualType* CompLHSTy) {
   checkArithmeticNull(*this, LHS, RHS, Loc, /*isCompare=*/false);
 
   if (LHS.get()->getType()->isVectorType() ||
@@ -5973,6 +6014,10 @@ QualType Sema::CheckAdditionOperands( // C99 6.5.6
   if (LHS.isInvalid() || RHS.isInvalid())
     return QualType();
 
+  // Diagnose "string literal" '+' int.
+  if (Opc == BO_Add)
+    diagnoseStringPlusInt(*this, Loc, LHS.get(), RHS.get());
+
   // handle the common case first (both operands are arithmetic).
   if (LHS.get()->getType()->isArithmeticType() &&
       RHS.get()->getType()->isArithmeticType()) {
@@ -7669,7 +7714,7 @@ ExprResult Sema::CreateBuiltinBinOp(SourceLocation OpLoc,
     ResultTy = CheckRemainderOperands(LHS, RHS, OpLoc);
     break;
   case BO_Add:
-    ResultTy = CheckAdditionOperands(LHS, RHS, OpLoc);
+    ResultTy = CheckAdditionOperands(LHS, RHS, OpLoc, Opc);
     break;
   case BO_Sub:
     ResultTy = CheckSubtractionOperands(LHS, RHS, OpLoc);
@@ -7712,7 +7757,7 @@ ExprResult Sema::CreateBuiltinBinOp(SourceLocation OpLoc,
       ResultTy = CheckAssignmentOperands(LHS.get(), RHS, OpLoc, CompResultTy);
     break;
   case BO_AddAssign:
-    CompResultTy = CheckAdditionOperands(LHS, RHS, OpLoc, &CompLHSTy);
+    CompResultTy = CheckAdditionOperands(LHS, RHS, OpLoc, Opc, &CompLHSTy);
     if (!CompResultTy.isNull() && !LHS.isInvalid() && !RHS.isInvalid())
       ResultTy = CheckAssignmentOperands(LHS.get(), RHS, OpLoc, CompResultTy);
     break;