[clang] [clang][Preprocessor] Add peekNextPPToken, makes look ahead next token without side-effects (PR #143898)
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Fri Jun 13 23:29:39 PDT 2025
https://github.com/yronglin updated https://github.com/llvm/llvm-project/pull/143898
>From 373daed324ca99f0b327c424c64a101f7d0f99a3 Mon Sep 17 00:00:00 2001
From: yronglin <yronglin777 at gmail.com>
Date: Thu, 12 Jun 2025 21:46:13 +0800
Subject: [PATCH 1/2] [Clang] Add peekNextPPToken, makes peek next token
without side-effects
Signed-off-by: yronglin <yronglin777 at gmail.com>
---
clang/include/clang/Lex/Lexer.h | 10 ++++----
clang/include/clang/Lex/Preprocessor.h | 8 ++++++-
clang/include/clang/Lex/TokenLexer.h | 7 +++---
clang/lib/Lex/Lexer.cpp | 21 +++++++++--------
clang/lib/Lex/PPMacroExpansion.cpp | 32 ++++++++++++--------------
clang/lib/Lex/TokenLexer.cpp | 10 ++++----
6 files changed, 46 insertions(+), 42 deletions(-)
diff --git a/clang/include/clang/Lex/Lexer.h b/clang/include/clang/Lex/Lexer.h
index bb65ae010cffa..a595cda1eaa77 100644
--- a/clang/include/clang/Lex/Lexer.h
+++ b/clang/include/clang/Lex/Lexer.h
@@ -124,7 +124,7 @@ class Lexer : public PreprocessorLexer {
//===--------------------------------------------------------------------===//
// Context that changes as the file is lexed.
// NOTE: any state that mutates when in raw mode must have save/restore code
- // in Lexer::isNextPPTokenLParen.
+ // in Lexer::peekNextPPToken.
// BufferPtr - Current pointer into the buffer. This is the next character
// to be lexed.
@@ -642,10 +642,10 @@ class Lexer : public PreprocessorLexer {
BufferPtr = TokEnd;
}
- /// isNextPPTokenLParen - Return 1 if the next unexpanded token will return a
- /// tok::l_paren token, 0 if it is something else and 2 if there are no more
- /// tokens in the buffer controlled by this lexer.
- unsigned isNextPPTokenLParen();
+ /// peekNextPPToken - Return std::nullopt if there are no more tokens in the
+ /// buffer controlled by this lexer, otherwise return the next unexpanded
+ /// token.
+ std::optional<Token> peekNextPPToken();
//===--------------------------------------------------------------------===//
// Lexer character reading interfaces.
diff --git a/clang/include/clang/Lex/Preprocessor.h b/clang/include/clang/Lex/Preprocessor.h
index 78be2bd64d61c..4fe7a79393afc 100644
--- a/clang/include/clang/Lex/Preprocessor.h
+++ b/clang/include/clang/Lex/Preprocessor.h
@@ -2288,7 +2288,9 @@ class Preprocessor {
/// Determine whether the next preprocessor token to be
/// lexed is a '('. If so, consume the token and return true, if not, this
/// method should have no observable side-effect on the lexed tokens.
- bool isNextPPTokenLParen();
+ bool isNextPPTokenLParen() {
+ return peekNextPPToken().value_or(Token{}).is(tok::l_paren);
+ }
private:
/// Identifiers used for SEH handling in Borland. These are only
@@ -2667,6 +2669,10 @@ class Preprocessor {
void removeCachedMacroExpandedTokensOfLastLexer();
+ /// Peek the next token. If so, return the token, if not, this
+ /// method should have no observable side-effect on the lexed tokens.
+ std::optional<Token> peekNextPPToken();
+
/// After reading "MACRO(", this method is invoked to read all of the formal
/// arguments specified for the macro invocation. Returns null on error.
MacroArgs *ReadMacroCallArgumentList(Token &MacroName, MacroInfo *MI,
diff --git a/clang/include/clang/Lex/TokenLexer.h b/clang/include/clang/Lex/TokenLexer.h
index 4d229ae610674..777b4e6266c71 100644
--- a/clang/include/clang/Lex/TokenLexer.h
+++ b/clang/include/clang/Lex/TokenLexer.h
@@ -139,10 +139,9 @@ class TokenLexer {
void Init(const Token *TokArray, unsigned NumToks, bool DisableMacroExpansion,
bool OwnsTokens, bool IsReinject);
- /// If the next token lexed will pop this macro off the
- /// expansion stack, return 2. If the next unexpanded token is a '(', return
- /// 1, otherwise return 0.
- unsigned isNextTokenLParen() const;
+ /// If the next token lexed will pop this macro off the expansion stack,
+ /// return std::nullopt, otherwise return the next unexpanded token.
+ std::optional<Token> peekNextPPToken() const;
/// Lex and return a token from this macro stream.
bool Lex(Token &Tok);
diff --git a/clang/lib/Lex/Lexer.cpp b/clang/lib/Lex/Lexer.cpp
index 93200458f04b4..8e977eac8c983 100644
--- a/clang/lib/Lex/Lexer.cpp
+++ b/clang/lib/Lex/Lexer.cpp
@@ -3200,18 +3200,19 @@ bool Lexer::LexEndOfFile(Token &Result, const char *CurPtr) {
return PP->HandleEndOfFile(Result, isPragmaLexer());
}
-/// isNextPPTokenLParen - Return 1 if the next unexpanded token lexed from
-/// the specified lexer will return a tok::l_paren token, 0 if it is something
-/// else and 2 if there are no more tokens in the buffer controlled by the
-/// lexer.
-unsigned Lexer::isNextPPTokenLParen() {
+/// peekNextPPToken - Return std::nullopt if there are no more tokens in the
+/// buffer controlled by this lexer, otherwise return the next unexpanded
+/// token.
+std::optional<Token> Lexer::peekNextPPToken() {
assert(!LexingRawMode && "How can we expand a macro from a skipping buffer?");
if (isDependencyDirectivesLexer()) {
if (NextDepDirectiveTokenIndex == DepDirectives.front().Tokens.size())
- return 2;
- return DepDirectives.front().Tokens[NextDepDirectiveTokenIndex].is(
- tok::l_paren);
+ return std::nullopt;
+ Token Result;
+ (void)convertDependencyDirectiveToken(
+ DepDirectives.front().Tokens[NextDepDirectiveTokenIndex], Result);
+ return Result;
}
// Switch to 'skipping' mode. This will ensure that we can lex a token
@@ -3240,8 +3241,8 @@ unsigned Lexer::isNextPPTokenLParen() {
LexingRawMode = false;
if (Tok.is(tok::eof))
- return 2;
- return Tok.is(tok::l_paren);
+ return std::nullopt;
+ return Tok;
}
/// Find the end of a version control conflict marker.
diff --git a/clang/lib/Lex/PPMacroExpansion.cpp b/clang/lib/Lex/PPMacroExpansion.cpp
index 37ac1bf07e9c0..585990f60c98a 100644
--- a/clang/lib/Lex/PPMacroExpansion.cpp
+++ b/clang/lib/Lex/PPMacroExpansion.cpp
@@ -418,42 +418,40 @@ static bool isTrivialSingleTokenExpansion(const MacroInfo *MI,
return !llvm::is_contained(MI->params(), II);
}
-/// isNextPPTokenLParen - Determine whether the next preprocessor token to be
-/// lexed is a '('. If so, consume the token and return true, if not, this
-/// method should have no observable side-effect on the lexed tokens.
-bool Preprocessor::isNextPPTokenLParen() {
+/// isNextPPTokenLParen - Peek the next token. If so, return the token, if not,
+/// this method should have no observable side-effect on the lexed tokens.
+std::optional<Token> Preprocessor::peekNextPPToken() {
// Do some quick tests for rejection cases.
- unsigned Val;
+ std::optional<Token> Val;
if (CurLexer)
- Val = CurLexer->isNextPPTokenLParen();
+ Val = CurLexer->peekNextPPToken();
else
- Val = CurTokenLexer->isNextTokenLParen();
+ Val = CurTokenLexer->peekNextPPToken();
- if (Val == 2) {
+ if (!Val) {
// We have run off the end. If it's a source file we don't
// examine enclosing ones (C99 5.1.1.2p4). Otherwise walk up the
// macro stack.
if (CurPPLexer)
- return false;
+ return std::nullopt;
for (const IncludeStackInfo &Entry : llvm::reverse(IncludeMacroStack)) {
if (Entry.TheLexer)
- Val = Entry.TheLexer->isNextPPTokenLParen();
+ Val = Entry.TheLexer->peekNextPPToken();
else
- Val = Entry.TheTokenLexer->isNextTokenLParen();
+ Val = Entry.TheTokenLexer->peekNextPPToken();
- if (Val != 2)
+ if (Val)
break;
// Ran off the end of a source file?
if (Entry.ThePPLexer)
- return false;
+ return std::nullopt;
}
}
- // Okay, if we know that the token is a '(', lex it and return. Otherwise we
- // have found something that isn't a '(' or we found the end of the
- // translation unit. In either case, return false.
- return Val == 1;
+ // Okay, we found the token and return. Otherwise we found the end of the
+ // translation unit.
+ return Val;
}
/// HandleMacroExpandedIdentifier - If an identifier token is read that is to be
diff --git a/clang/lib/Lex/TokenLexer.cpp b/clang/lib/Lex/TokenLexer.cpp
index 6e93416e01c0c..fbb8c4262d6da 100644
--- a/clang/lib/Lex/TokenLexer.cpp
+++ b/clang/lib/Lex/TokenLexer.cpp
@@ -921,13 +921,13 @@ bool TokenLexer::pasteTokens(Token &LHSTok, ArrayRef<Token> TokenStream,
}
/// isNextTokenLParen - If the next token lexed will pop this macro off the
-/// expansion stack, return 2. If the next unexpanded token is a '(', return
-/// 1, otherwise return 0.
-unsigned TokenLexer::isNextTokenLParen() const {
+/// expansion stack, return std::nullopt, otherwise return the next unexpanded
+/// token.
+std::optional<Token> TokenLexer::peekNextPPToken() const {
// Out of tokens?
if (isAtEnd())
- return 2;
- return Tokens[CurTokenIdx].is(tok::l_paren);
+ return std::nullopt;
+ return Tokens[CurTokenIdx];
}
/// isParsingPreprocessorDirective - Return true if we are in the middle of a
>From c963c3a9cdb7835e5c031bf7a1f82e61f0c15e42 Mon Sep 17 00:00:00 2001
From: yronglin <yronglin777 at gmail.com>
Date: Sat, 14 Jun 2025 14:29:16 +0800
Subject: [PATCH 2/2] Update peekNextToken to isNextPPTokenOneOf
Signed-off-by: yronglin <yronglin777 at gmail.com>
---
clang/include/clang/Lex/Preprocessor.h | 41 +++++++++++++++++++++-----
clang/lib/Lex/PPDirectives.cpp | 4 +--
clang/lib/Lex/PPMacroExpansion.cpp | 36 ----------------------
clang/lib/Lex/Preprocessor.cpp | 4 +--
4 files changed, 37 insertions(+), 48 deletions(-)
diff --git a/clang/include/clang/Lex/Preprocessor.h b/clang/include/clang/Lex/Preprocessor.h
index 4fe7a79393afc..f5e85b3da1ba1 100644
--- a/clang/include/clang/Lex/Preprocessor.h
+++ b/clang/include/clang/Lex/Preprocessor.h
@@ -2285,11 +2285,40 @@ class Preprocessor {
}
}
- /// Determine whether the next preprocessor token to be
- /// lexed is a '('. If so, consume the token and return true, if not, this
+ /// Check whether the next pp-token is one of the specificed token kind. this
/// method should have no observable side-effect on the lexed tokens.
- bool isNextPPTokenLParen() {
- return peekNextPPToken().value_or(Token{}).is(tok::l_paren);
+ template <tok::TokenKind K, tok::TokenKind... Ks> bool isNextPPTokenOneOf() {
+ // Do some quick tests for rejection cases.
+ std::optional<Token> Val;
+ if (CurLexer)
+ Val = CurLexer->peekNextPPToken();
+ else
+ Val = CurTokenLexer->peekNextPPToken();
+
+ if (!Val) {
+ // We have run off the end. If it's a source file we don't
+ // examine enclosing ones (C99 5.1.1.2p4). Otherwise walk up the
+ // macro stack.
+ if (CurPPLexer)
+ return false;
+ for (const IncludeStackInfo &Entry : llvm::reverse(IncludeMacroStack)) {
+ if (Entry.TheLexer)
+ Val = Entry.TheLexer->peekNextPPToken();
+ else
+ Val = Entry.TheTokenLexer->peekNextPPToken();
+
+ if (Val)
+ break;
+
+ // Ran off the end of a source file?
+ if (Entry.ThePPLexer)
+ return false;
+ }
+ }
+
+ // Okay, we found the token and return. Otherwise we found the end of the
+ // translation unit.
+ return Val->is(K) || (... || Val->is(Ks));
}
private:
@@ -2669,10 +2698,6 @@ class Preprocessor {
void removeCachedMacroExpandedTokensOfLastLexer();
- /// Peek the next token. If so, return the token, if not, this
- /// method should have no observable side-effect on the lexed tokens.
- std::optional<Token> peekNextPPToken();
-
/// After reading "MACRO(", this method is invoked to read all of the formal
/// arguments specified for the macro invocation. Returns null on error.
MacroArgs *ReadMacroCallArgumentList(Token &MacroName, MacroInfo *MI,
diff --git a/clang/lib/Lex/PPDirectives.cpp b/clang/lib/Lex/PPDirectives.cpp
index 04a30f66fb736..be061f462f65a 100644
--- a/clang/lib/Lex/PPDirectives.cpp
+++ b/clang/lib/Lex/PPDirectives.cpp
@@ -183,9 +183,9 @@ static bool isReservedCXXAttributeName(Preprocessor &PP, IdentifierInfo *II) {
AttributeCommonInfo::AttrArgsInfo AttrArgsInfo =
AttributeCommonInfo::getCXX11AttrArgsInfo(II);
if (AttrArgsInfo == AttributeCommonInfo::AttrArgsInfo::Required)
- return PP.isNextPPTokenLParen();
+ return PP.isNextPPTokenOneOf<tok::l_paren>();
- return !PP.isNextPPTokenLParen() ||
+ return !PP.isNextPPTokenOneOf<tok::l_paren>() ||
AttrArgsInfo == AttributeCommonInfo::AttrArgsInfo::Optional;
}
return false;
diff --git a/clang/lib/Lex/PPMacroExpansion.cpp b/clang/lib/Lex/PPMacroExpansion.cpp
index 585990f60c98a..b8b91e32179af 100644
--- a/clang/lib/Lex/PPMacroExpansion.cpp
+++ b/clang/lib/Lex/PPMacroExpansion.cpp
@@ -418,42 +418,6 @@ static bool isTrivialSingleTokenExpansion(const MacroInfo *MI,
return !llvm::is_contained(MI->params(), II);
}
-/// isNextPPTokenLParen - Peek the next token. If so, return the token, if not,
-/// this method should have no observable side-effect on the lexed tokens.
-std::optional<Token> Preprocessor::peekNextPPToken() {
- // Do some quick tests for rejection cases.
- std::optional<Token> Val;
- if (CurLexer)
- Val = CurLexer->peekNextPPToken();
- else
- Val = CurTokenLexer->peekNextPPToken();
-
- if (!Val) {
- // We have run off the end. If it's a source file we don't
- // examine enclosing ones (C99 5.1.1.2p4). Otherwise walk up the
- // macro stack.
- if (CurPPLexer)
- return std::nullopt;
- for (const IncludeStackInfo &Entry : llvm::reverse(IncludeMacroStack)) {
- if (Entry.TheLexer)
- Val = Entry.TheLexer->peekNextPPToken();
- else
- Val = Entry.TheTokenLexer->peekNextPPToken();
-
- if (Val)
- break;
-
- // Ran off the end of a source file?
- if (Entry.ThePPLexer)
- return std::nullopt;
- }
- }
-
- // Okay, we found the token and return. Otherwise we found the end of the
- // translation unit.
- return Val;
-}
-
/// HandleMacroExpandedIdentifier - If an identifier token is read that is to be
/// expanded as a macro, handle it and return the next token as 'Identifier'.
bool Preprocessor::HandleMacroExpandedIdentifier(Token &Identifier,
diff --git a/clang/lib/Lex/Preprocessor.cpp b/clang/lib/Lex/Preprocessor.cpp
index 21fc7a2b6fae2..f28113e569218 100644
--- a/clang/lib/Lex/Preprocessor.cpp
+++ b/clang/lib/Lex/Preprocessor.cpp
@@ -811,14 +811,14 @@ bool Preprocessor::HandleIdentifier(Token &Identifier) {
if (!Identifier.isExpandDisabled() && MI->isEnabled()) {
// C99 6.10.3p10: If the preprocessing token immediately after the
// macro name isn't a '(', this macro should not be expanded.
- if (!MI->isFunctionLike() || isNextPPTokenLParen())
+ if (!MI->isFunctionLike() || isNextPPTokenOneOf<tok::l_paren>())
return HandleMacroExpandedIdentifier(Identifier, MD);
} else {
// C99 6.10.3.4p2 says that a disabled macro may never again be
// expanded, even if it's in a context where it could be expanded in the
// future.
Identifier.setFlag(Token::DisableExpand);
- if (MI->isObjectLike() || isNextPPTokenLParen())
+ if (MI->isObjectLike() || isNextPPTokenOneOf<tok::l_paren>())
Diag(Identifier, diag::pp_disabled_macro_expansion);
}
}
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