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[clang][Lexer] Make raw and normal lexer behave the same for line comments

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Normally there are heruistics in lexer to treat `//*` specially in
language modes that don't have line comments (to emit `/`). Unfortunately this
only applied to the first occurence of a line comment inside the file, as the
subsequent line comments were treated as if language had support for them.

This unfortunately only holds in normal lexing mode, as in raw mode all
occurences of line comments received this treatment, which created discrepancies
when comparing expanded and spelled tokens.

The proper fix would be to just make sure we treat all the line comments with a
subsequent `*` the same way, but it would imply breaking some code that's
accepted by clang today. So instead we introduce the same bug into raw lexing
mode.

Fixes https://github.com/clangd/clangd/issues/1003.

Differential Revision: https://reviews.llvm.org/D118471
This commit is contained in:
Kadir Cetinkaya
2022-01-28 16:18:24 +01:00
parent 8faad29634
commit ff77071a4d
2 changed files with 28 additions and 2 deletions
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5
clang/lib/Lex/Lexer.cpp
View File

@@ -2378,8 +2378,9 @@ bool Lexer::SkipLineComment(Token &Result, const char *CurPtr,
bool &TokAtPhysicalStartOfLine) {
// If Line comments aren't explicitly enabled for this language, emit an
// extension warning.
if (!LangOpts.LineComment && !isLexingRawMode()) {
Diag(BufferPtr, diag::ext_line_comment);
if (!LangOpts.LineComment) {
if (!isLexingRawMode()) // There's no PP in raw mode, so can't emit diags.
Diag(BufferPtr, diag::ext_line_comment);
// Mark them enabled so we only emit one warning for this translation
// unit.

25
clang/unittests/Lex/LexerTest.cpp
View File

@@ -23,6 +23,8 @@
#include "clang/Lex/ModuleLoader.h"
#include "clang/Lex/Preprocessor.h"
#include "clang/Lex/PreprocessorOptions.h"
#include "llvm/ADT/ArrayRef.h"
#include "llvm/ADT/StringRef.h"
#include "gmock/gmock.h"
#include "gtest/gtest.h"
#include <memory>
@@ -632,4 +634,27 @@ TEST_F(LexerTest, CreatedFIDCountForPredefinedBuffer) {
EXPECT_EQ(SourceMgr.getNumCreatedFIDsForFileID(PP->getPredefinesFileID()),
1U);
}
TEST_F(LexerTest, RawAndNormalLexSameForLineComments) {
const llvm::StringLiteral Source = R"cpp(
// First line comment.
//* Second line comment which is ambigious.
)cpp";
LangOpts.LineComment = false;
auto Toks = Lex(Source);
auto &SM = PP->getSourceManager();
auto SrcBuffer = SM.getBufferData(SM.getMainFileID());
Lexer L(SM.getLocForStartOfFile(SM.getMainFileID()), PP->getLangOpts(),
SrcBuffer.data(), SrcBuffer.data(),
SrcBuffer.data() + SrcBuffer.size());
auto ToksView = llvm::makeArrayRef(Toks);
clang::Token T;
while (!L.LexFromRawLexer(T)) {
ASSERT_TRUE(!ToksView.empty());
EXPECT_EQ(T.getKind(), ToksView.front().getKind());
ToksView = ToksView.drop_front();
}
EXPECT_TRUE(ToksView.empty());
}
} // anonymous namespace