[Clang] Allow raw string literals in C as an extension

clang/docs/ReleaseNotes.rst

@@ -43,6 +43,9 @@ code bases.
 C/C++ Language Potentially Breaking Changes
 -------------------------------------------
 
+- Clang now supports raw string literals in ``-std=gnuXY`` mode as an extension in
+  C. This behaviour can also be overridden using ``-f[no-]raw-string-literals``.
+
 C++ Specific Potentially Breaking Changes
 -----------------------------------------
 - Clang now diagnoses function/variable templates that shadow their own template parameters, e.g. ``template<class T> void T();``.

clang/include/clang/Basic/LangOptions.def

@@ -454,6 +454,8 @@ LANGOPT(MatrixTypes, 1, 0, "Enable or disable the builtin matrix type")
 
 LANGOPT(CXXAssumptions, 1, 1, "Enable or disable codegen and compile-time checks for C++23's [[assume]] attribute")
 
+LANGOPT(RawStringLiterals, 1, 0, "Enable or disable raw string literals")
+
 ENUM_LANGOPT(StrictFlexArraysLevel, StrictFlexArraysLevelKind, 2,
              StrictFlexArraysLevelKind::Default,
              "Rely on strict definition of flexible arrays")

clang/include/clang/Basic/LangStandard.h

@@ -130,6 +130,12 @@ struct LangStandard {
   /// hasDigraphs - Language supports digraphs.
   bool hasDigraphs() const { return Flags & Digraphs; }
 
+  /// hasRawStringLiterals - Language supports R"()" raw string literals.
+  bool hasRawStringLiterals() const {
+    // GCC supports raw string literals in C, but not in C++ before C++11.
+    return isCPlusPlus11() || (!isCPlusPlus() && isGNUMode());
+  }
+
   /// isGNUMode - Language includes GNU extensions.
   bool isGNUMode() const { return Flags & GNUMode; }
 

clang/include/clang/Driver/Options.td

@@ -4142,6 +4142,12 @@ def fenable_matrix : Flag<["-"], "fenable-matrix">, Group<f_Group>,
     HelpText<"Enable matrix data type and related builtin functions">,
     MarshallingInfoFlag<LangOpts<"MatrixTypes">>;
 
+defm raw_string_literals : BoolFOption<"raw-string-literals",
+    LangOpts<"RawStringLiterals">, Default<std#".hasRawStringLiterals()">,
+    PosFlag<SetTrue, [], [], "Enable">,
+    NegFlag<SetFalse, [], [], "Disable">,
+    BothFlags<[], [ClangOption, CC1Option], " raw string literals">>;
+
 def fzero_call_used_regs_EQ
     : Joined<["-"], "fzero-call-used-regs=">, Group<f_Group>,
     Visibility<[ClangOption, CC1Option]>,

clang/lib/Basic/LangOptions.cpp

@@ -124,6 +124,7 @@ void LangOptions::setLangDefaults(LangOptions &Opts, Language Lang,
   Opts.HexFloats = Std.hasHexFloats();
   Opts.WChar = Std.isCPlusPlus();
   Opts.Digraphs = Std.hasDigraphs();
+  Opts.RawStringLiterals = Std.hasRawStringLiterals();
 
   Opts.HLSL = Lang == Language::HLSL;
   if (Opts.HLSL && Opts.IncludeDefaultHeader)

clang/lib/Driver/ToolChains/Clang.cpp

@@ -6536,6 +6536,8 @@ void Clang::ConstructJob(Compilation &C, const JobAction &JA,
   Args.AddLastArg(CmdArgs, options::OPT_fheinous_gnu_extensions);
   Args.AddLastArg(CmdArgs, options::OPT_fdigraphs, options::OPT_fno_digraphs);
   Args.AddLastArg(CmdArgs, options::OPT_fzero_call_used_regs_EQ);
+  Args.AddLastArg(CmdArgs, options::OPT_fraw_string_literals,
+                  options::OPT_fno_raw_string_literals);
 
   if (Args.hasFlag(options::OPT_femulated_tls, options::OPT_fno_emulated_tls,
                    Triple.hasDefaultEmulatedTLS()))

clang/lib/Format/Format.cpp

@@ -3850,6 +3850,7 @@ LangOptions getFormattingLangOpts(const FormatStyle &Style) {
   // the sequence "<::" will be unconditionally treated as "[:".
   // Cf. Lexer::LexTokenInternal.
   LangOpts.Digraphs = LexingStd >= FormatStyle::LS_Cpp11;
+  LangOpts.RawStringLiterals = LexingStd >= FormatStyle::LS_Cpp11;
 
   LangOpts.LineComment = 1;
   bool AlternativeOperators = Style.isCpp();

clang/lib/Lex/Lexer.cpp

@@ -3867,7 +3867,7 @@ bool Lexer::LexTokenInternal(Token &Result, bool TokAtPhysicalStartOfLine) {
                                tok::utf16_char_constant);
 
       // UTF-16 raw string literal
-      if (Char == 'R' && LangOpts.CPlusPlus11 &&
+      if (Char == 'R' && LangOpts.RawStringLiterals &&
           getCharAndSize(CurPtr + SizeTmp, SizeTmp2) == '"')
         return LexRawStringLiteral(Result,
                                ConsumeChar(ConsumeChar(CurPtr, SizeTmp, Result),
@@ -3889,7 +3889,7 @@ bool Lexer::LexTokenInternal(Token &Result, bool TokAtPhysicalStartOfLine) {
                                   SizeTmp2, Result),
               tok::utf8_char_constant);
 
-        if (Char2 == 'R' && LangOpts.CPlusPlus11) {
+        if (Char2 == 'R' && LangOpts.RawStringLiterals) {
           unsigned SizeTmp3;
           char Char3 = getCharAndSize(CurPtr + SizeTmp + SizeTmp2, SizeTmp3);
           // UTF-8 raw string literal
@@ -3925,7 +3925,7 @@ bool Lexer::LexTokenInternal(Token &Result, bool TokAtPhysicalStartOfLine) {
                                tok::utf32_char_constant);
 
       // UTF-32 raw string literal
-      if (Char == 'R' && LangOpts.CPlusPlus11 &&
+      if (Char == 'R' && LangOpts.RawStringLiterals &&
           getCharAndSize(CurPtr + SizeTmp, SizeTmp2) == '"')
         return LexRawStringLiteral(Result,
                                ConsumeChar(ConsumeChar(CurPtr, SizeTmp, Result),
@@ -3940,7 +3940,7 @@ bool Lexer::LexTokenInternal(Token &Result, bool TokAtPhysicalStartOfLine) {
     // Notify MIOpt that we read a non-whitespace/non-comment token.
     MIOpt.ReadToken();
 
-    if (LangOpts.CPlusPlus11) {
+    if (LangOpts.RawStringLiterals) {
       Char = getCharAndSize(CurPtr, SizeTmp);
 
       if (Char == '"')
@@ -3963,7 +3963,7 @@ bool Lexer::LexTokenInternal(Token &Result, bool TokAtPhysicalStartOfLine) {
                               tok::wide_string_literal);
 
     // Wide raw string literal.
-    if (LangOpts.CPlusPlus11 && Char == 'R' &&
+    if (LangOpts.RawStringLiterals && Char == 'R' &&
         getCharAndSize(CurPtr + SizeTmp, SizeTmp2) == '"')
       return LexRawStringLiteral(Result,
                                ConsumeChar(ConsumeChar(CurPtr, SizeTmp, Result),

clang/test/Lexer/raw-string-ext.c

@@ -0,0 +1,18 @@
+// RUN: %clang_cc1 -fsyntax-only -std=gnu11 -verify=gnu -DGNU %s
+// RUN: %clang_cc1 -fsyntax-only -std=c11 -fraw-string-literals -verify=gnu -DGNU %s
+// RUN: %clang_cc1 -fsyntax-only -std=c11 -verify=std %s
+// RUN: %clang_cc1 -fsyntax-only -std=gnu11 -fno-raw-string-literals -verify=std %s
+
+void f() {
+  (void) R"foo()foo"; // std-error {{use of undeclared identifier 'R'}}
+  (void) LR"foo()foo"; // std-error {{use of undeclared identifier 'LR'}}
+  (void) uR"foo()foo"; // std-error {{use of undeclared identifier 'uR'}}
+  (void) u8R"foo()foo"; // std-error {{use of undeclared identifier 'u8R'}}
+  (void) UR"foo()foo"; // std-error {{use of undeclared identifier 'UR'}}
+}
+
+// gnu-error@* {{missing terminating delimiter}}
+// gnu-error@* {{expected expression}}
+// gnu-error@* {{expected ';' after top level declarator}}
+#define R "bar"
+const char* s =  R"foo(";