release/20.x: [clang] Introduce "binary" StringLiteral for #embed data (#127629)

clang/include/clang/AST/Expr.h

@@ -1752,7 +1752,14 @@ enum class StringLiteralKind {
   UTF8,
   UTF16,
   UTF32,
-  Unevaluated
+  Unevaluated,
+  // Binary kind of string literal is used for the data coming via #embed
+  // directive. File's binary contents is transformed to a special kind of
+  // string literal that in some cases may be used directly as an initializer
+  // and some features of classic string literals are not applicable to this
+  // kind of a string literal, for example finding a particular byte's source
+  // location for better diagnosing.
+  Binary
 };
 
 /// StringLiteral - This represents a string literal expression, e.g. "foo"
@@ -1884,6 +1891,8 @@ class StringLiteral final
   int64_t getCodeUnitS(size_t I, uint64_t BitWidth) const {
     int64_t V = getCodeUnit(I);
     if (isOrdinary() || isWide()) {
+      // Ordinary and wide string literals have types that can be signed.
+      // It is important for checking C23 constexpr initializers.
       unsigned Width = getCharByteWidth() * BitWidth;
       llvm::APInt AInt(Width, (uint64_t)V);
       V = AInt.getSExtValue();
@@ -4965,9 +4974,9 @@ class EmbedExpr final : public Expr {
       assert(EExpr && CurOffset != ULLONG_MAX &&
              "trying to dereference an invalid iterator");
       IntegerLiteral *N = EExpr->FakeChildNode;
-      StringRef DataRef = EExpr->Data->BinaryData->getBytes();
       N->setValue(*EExpr->Ctx,
-                  llvm::APInt(N->getValue().getBitWidth(), DataRef[CurOffset],
+                  llvm::APInt(N->getValue().getBitWidth(),
+                              EExpr->Data->BinaryData->getCodeUnit(CurOffset),
                               N->getType()->isSignedIntegerType()));
       // We want to return a reference to the fake child node in the
       // EmbedExpr, not the local variable N.

clang/lib/AST/Expr.cpp

@@ -1104,6 +1104,7 @@ unsigned StringLiteral::mapCharByteWidth(TargetInfo const &Target,
   switch (SK) {
   case StringLiteralKind::Ordinary:
   case StringLiteralKind::UTF8:
+  case StringLiteralKind::Binary:
     CharByteWidth = Target.getCharWidth();
     break;
   case StringLiteralKind::Wide:
@@ -1216,6 +1217,7 @@ void StringLiteral::outputString(raw_ostream &OS) const {
   switch (getKind()) {
   case StringLiteralKind::Unevaluated:
   case StringLiteralKind::Ordinary:
+  case StringLiteralKind::Binary:
     break; // no prefix.
   case StringLiteralKind::Wide:
     OS << 'L';
@@ -1332,6 +1334,11 @@ StringLiteral::getLocationOfByte(unsigned ByteNo, const SourceManager &SM,
                                  const LangOptions &Features,
                                  const TargetInfo &Target, unsigned *StartToken,
                                  unsigned *StartTokenByteOffset) const {
+  // No source location of bytes for binary literals since they don't come from
+  // source.
+  if (getKind() == StringLiteralKind::Binary)
+    return getStrTokenLoc(0);
+
   assert((getKind() == StringLiteralKind::Ordinary ||
           getKind() == StringLiteralKind::UTF8 ||
           getKind() == StringLiteralKind::Unevaluated) &&

clang/lib/Parse/ParseInit.cpp

@@ -445,7 +445,7 @@ ExprResult Parser::createEmbedExpr() {
           Context.MakeIntValue(Str.size(), Context.getSizeType());
       QualType ArrayTy = Context.getConstantArrayType(
           Ty, ArraySize, nullptr, ArraySizeModifier::Normal, 0);
-      return StringLiteral::Create(Context, Str, StringLiteralKind::Ordinary,
+      return StringLiteral::Create(Context, Str, StringLiteralKind::Binary,
                                    false, ArrayTy, StartLoc);
     };
 

clang/lib/Sema/SemaExprCXX.cpp

@@ -4143,6 +4143,7 @@ Sema::IsStringLiteralToNonConstPointerConversion(Expr *From, QualType ToType) {
             // We don't allow UTF literals to be implicitly converted
             break;
           case StringLiteralKind::Ordinary:
+          case StringLiteralKind::Binary:
             return (ToPointeeType->getKind() == BuiltinType::Char_U ||
                     ToPointeeType->getKind() == BuiltinType::Char_S);
           case StringLiteralKind::Wide:

clang/lib/Sema/SemaInit.cpp

@@ -105,6 +105,7 @@ static StringInitFailureKind IsStringInit(Expr *Init, const ArrayType *AT,
       return SIF_None;
     [[fallthrough]];
   case StringLiteralKind::Ordinary:
+  case StringLiteralKind::Binary:
     // char array can be initialized with a narrow string.
     // Only allow char x[] = "foo";  not char x[] = L"foo";
     if (ElemTy->isCharType())

clang/test/Preprocessor/embed_constexpr.c

@@ -0,0 +1,21 @@
+// RUN: %clang_cc1 %s -fsyntax-only --embed-dir=%S/Inputs -verify -std=c23
+
+static constexpr unsigned char data[] = {
+#embed "big_char.txt"
+};
+
+static constexpr char data1[] = {
+#embed "big_char.txt" // expected-error {{constexpr initializer evaluates to 255 which is not exactly representable in type 'const char'}}
+};
+
+static constexpr int data2[] = {
+#embed "big_char.txt"
+};
+
+static constexpr unsigned data3[] = {
+#embed "big_char.txt" suffix(, -1) // expected-error {{constexpr initializer evaluates to -1 which is not exactly representable in type 'const unsigned int'}}
+};
+
+static constexpr int data4[] = {
+#embed "big_char.txt" suffix(, -1)
+};