Commit 49e0495f authored by Corentin Jabot's avatar Corentin Jabot
Browse files

[Clang] Produce a warning instead of an error in unevaluated strings before C++26 

Emiting an error on unexpected encoding prefix - which was allowed before C++26 -
caused build errors for a few users.
This downgrade the error to a warning on older language modes and C.

Reviewed By: aaron.ballman, hubert.reinterpretcast

Differential Revision: https://reviews.llvm.org/D156596
parent b720dcba

clang/include/clang/Basic/DiagnosticLexKinds.td

+4 −0
Original line number Diff line number Diff line
@@ -285,6 +285,10 @@ def ext_ms_reserved_user_defined_literal : ExtWarn< 
def err_unsupported_string_concat : Error<

  "unsupported non-standard concatenation of string literals">;



def warn_unevaluated_string_prefix : Warning<

  "encoding prefix '%0' on an unevaluated string literal has no effect"

  "%select{| and is incompatible with c++2c}1">,

  InGroup<DiagGroup<"invalid-unevaluated-string">>;

def err_unevaluated_string_prefix : Error<

  "an unevaluated string literal cannot have an encoding prefix">;

def err_unevaluated_string_udl : Error<

clang/lib/Lex/LiteralSupport.cpp

+38 −3
Original line number Diff line number Diff line
@@ -57,6 +57,26 @@ static unsigned getCharWidth(tok::TokenKind kind, const TargetInfo &Target) { 
  }

}



static unsigned getEncodingPrefixLen(tok::TokenKind kind) {

  switch (kind) {

  default:

    llvm_unreachable("Unknown token type!");

  case tok::char_constant:

  case tok::string_literal:

    return 0;

  case tok::utf8_char_constant:

  case tok::utf8_string_literal:

    return 2;

  case tok::wide_char_constant:

  case tok::wide_string_literal:

  case tok::utf16_char_constant:

  case tok::utf16_string_literal:

  case tok::utf32_char_constant:

  case tok::utf32_string_literal:

    return 1;

  }

}



static CharSourceRange MakeCharSourceRange(const LangOptions &Features,

                                           FullSourceLoc TokLoc,

                                           const char *TokBegin,
@@ -343,7 +363,9 @@ static unsigned ProcessCharEscape(const char *ThisTokBegin, 
    Diag(Diags, Features, Loc, ThisTokBegin, EscapeBegin, ThisTokBuf,

         diag::err_unevaluated_string_invalid_escape_sequence)

        << StringRef(EscapeBegin, ThisTokBuf - EscapeBegin);

    HadError = true;

  }



  return ResultChar;

}
@@ -1930,8 +1952,21 @@ void StringLiteralParser::init(ArrayRef<Token> StringToks){ 
    // Remember if we see any wide or utf-8/16/32 strings.

    // Also check for illegal concatenations.

    if (isUnevaluated() && Tok.getKind() != tok::string_literal) {

      if (Diags)

        Diags->Report(Tok.getLocation(), diag::err_unevaluated_string_prefix);

      if (Diags) {

        SourceLocation PrefixEndLoc = Lexer::AdvanceToTokenCharacter(

            Tok.getLocation(), getEncodingPrefixLen(Tok.getKind()), SM,

            Features);

        CharSourceRange Range =

            CharSourceRange::getCharRange({Tok.getLocation(), PrefixEndLoc});

        StringRef Prefix(SM.getCharacterData(Tok.getLocation()),

                         getEncodingPrefixLen(Tok.getKind()));

        Diags->Report(Tok.getLocation(),

                      Features.CPlusPlus26

                          ? diag::err_unevaluated_string_prefix

                          : diag::warn_unevaluated_string_prefix)

            << Prefix << Features.CPlusPlus << FixItHint::CreateRemoval(Range);

      }

      if (Features.CPlusPlus26)

        hadError = true;

    } else if (Tok.isNot(Kind) && Tok.isNot(tok::string_literal)) {

      if (isOrdinary()) {

clang/lib/Parse/ParseDeclCXX.cpp

+1 −1
Original line number Diff line number Diff line
@@ -1023,7 +1023,7 @@ Decl *Parser::ParseStaticAssertDeclaration(SourceLocation &DeclEnd) { 
        const Token &T = GetLookAheadToken(I);

        if (T.is(tok::r_paren))

          break;

        if (T.isNot(tok::string_literal)) {

        if (!tokenIsLikeStringLiteral(T, getLangOpts())) {

          ParseAsExpression = true;

          break;

        }

clang/test/CXX/dcl.dcl/dcl.link/p2.cpp

+4 −4
Original line number Diff line number Diff line
@@ -8,7 +8,7 @@ extern "C" { 
extern "C" plusplus {

}



extern u8"C" {}  // expected-error {{an unevaluated string literal cannot have an encoding prefix}}

extern L"C" {}   // expected-error {{an unevaluated string literal cannot have an encoding prefix}}

extern u"C++" {} // expected-error {{an unevaluated string literal cannot have an encoding prefix}}

extern U"C" {}   // expected-error {{an unevaluated string literal cannot have an encoding prefix}}
 
extern u8"C" {}  // expected-warning {{encoding prefix 'u8' on an unevaluated string literal has no effect and is incompatible with c++2c}}

extern L"C" {}   // expected-warning {{encoding prefix 'L' on an unevaluated string literal has no effect and is incompatible with c++2c}}

extern u"C++" {} // expected-warning {{encoding prefix 'u' on an unevaluated string literal has no effect and is incompatible with c++2c}}

extern U"C" {}   // expected-warning {{encoding prefix 'U' on an unevaluated string literal has no effect and is incompatible with c++2c}}

clang/test/CXX/dcl.dcl/p4-0x.cpp

+1 −1
Original line number Diff line number Diff line
@@ -18,7 +18,7 @@ static_assert(S(false), "not so fast"); // expected-error {{not so fast}} 
static_assert(T(), "");

static_assert(U(), ""); // expected-error {{ambiguous}}



static_assert(false, L"\x14hi" // expected-error {{an unevaluated string literal cannot have an encoding prefix}} \

static_assert(false, L"\x14hi" // expected-warning {{encoding prefix 'L' on an unevaluated string literal has no effect and is incompatible with c++2c}} \

                               // expected-error {{invalid escape sequence '\x14' in an unevaluated string literal}}

                     "!"

                     R"x(")x");