[clang] [clang] Allow `$` in identifiers during preprocessing (PR #200614)
Matthias Wippich via cfe-commits
cfe-commits at lists.llvm.org
Thu Jun 4 17:51:11 PDT 2026
https://github.com/Tsche updated https://github.com/llvm/llvm-project/pull/200614
>From 4f0d13f79cfe3af808609a85ca3c8ff9df8b8f88 Mon Sep 17 00:00:00 2001
From: Matthias Wippich <mfwippich at gmail.com>
Date: Fri, 22 May 2026 04:17:22 +0200
Subject: [PATCH 1/9] initial attempt at allowing $ in macros unconditionally
---
.../include/clang/Basic/DiagnosticLexKinds.td | 3 ++
clang/include/clang/Basic/IdentifierTable.h | 15 +++++++-
clang/include/clang/Lex/Lexer.h | 3 +-
clang/include/clang/Lex/Preprocessor.h | 2 ++
clang/lib/Lex/Lexer.cpp | 34 +++++++++----------
clang/lib/Lex/Preprocessor.cpp | 21 ++++++++++--
clang/test/Lexer/dollar-macros.cpp | 27 +++++++++++++++
7 files changed, 83 insertions(+), 22 deletions(-)
create mode 100644 clang/test/Lexer/dollar-macros.cpp
diff --git a/clang/include/clang/Basic/DiagnosticLexKinds.td b/clang/include/clang/Basic/DiagnosticLexKinds.td
index 383bf1a7fdb3f..2eb90f788b122 100644
--- a/clang/include/clang/Basic/DiagnosticLexKinds.td
+++ b/clang/include/clang/Basic/DiagnosticLexKinds.td
@@ -55,6 +55,9 @@ def ext_line_comment : Extension<
def warn_no_newline_eof : Warning<"no newline at end of file">,
InGroup<NewlineEOF>, DefaultIgnore;
+def err_dollar_in_identifier : Error<
+ "identifier '%0' is not supported with the current configuration">;
+
def ext_dollar_in_identifier : Extension<"'$' in identifier">,
InGroup<DiagGroup<"dollar-in-identifier-extension">>;
def ext_charize_microsoft : Extension<
diff --git a/clang/include/clang/Basic/IdentifierTable.h b/clang/include/clang/Basic/IdentifierTable.h
index ff5864bc31927..b7b950910d9b0 100644
--- a/clang/include/clang/Basic/IdentifierTable.h
+++ b/clang/include/clang/Basic/IdentifierTable.h
@@ -256,7 +256,11 @@ class alignas(IdentifierInfoAlignment) IdentifierInfo {
LLVM_PREFERRED_TYPE(bool)
unsigned IsKeywordInCpp : 1;
- // 21 bits left in a 64-bit word.
+ // True if this identifier contains a $
+ LLVM_PREFERRED_TYPE(bool)
+ unsigned IsDollarIdentifier : 1;
+
+ // 20 bits left in a 64-bit word.
// Managed by the language front-end.
void *FETokenInfo = nullptr;
@@ -472,6 +476,15 @@ class alignas(IdentifierInfoAlignment) IdentifierInfo {
RecomputeNeedsHandleIdentifier();
}
+ bool isDollarIdentifier() const { return IsDollarIdentifier; }
+ void setDollarIdentifier(bool Val) {
+ IsDollarIdentifier = Val;
+ if (Val)
+ NeedsHandleIdentifier = true;
+ else
+ RecomputeNeedsHandleIdentifier();
+ }
+
/// is/setIsFutureCompatKeyword - Initialize information about whether or not
/// this language token is a keyword in a newer or proposed Standard. This
/// controls compatibility warnings, and is only true when not parsing the
diff --git a/clang/include/clang/Lex/Lexer.h b/clang/include/clang/Lex/Lexer.h
index b042e5fb088fa..d3f8ea3720d34 100644
--- a/clang/include/clang/Lex/Lexer.h
+++ b/clang/include/clang/Lex/Lexer.h
@@ -759,7 +759,8 @@ class Lexer : public PreprocessorLexer {
// This function handles both ASCII and Unicode identifiers after
// the first codepoint of the identifyier has been parsed.
- bool LexIdentifierContinue(Token &Result, const char *CurPtr);
+ bool LexIdentifierContinue(Token &Result, const char *CurPtr,
+ bool HasDollar = false);
bool LexNumericConstant (Token &Result, const char *CurPtr);
bool LexStringLiteral (Token &Result, const char *CurPtr,
diff --git a/clang/include/clang/Lex/Preprocessor.h b/clang/include/clang/Lex/Preprocessor.h
index 8b684e85eb1c1..cf3a04fd24e38 100644
--- a/clang/include/clang/Lex/Preprocessor.h
+++ b/clang/include/clang/Lex/Preprocessor.h
@@ -2398,6 +2398,8 @@ class Preprocessor {
public:
void PoisonSEHIdentifiers(bool Poison = true); // Borland
+ bool HandleDollarIdentifier(Token &Identifier);
+
/// Callback invoked when the lexer reads an identifier and has
/// filled in the tokens IdentifierInfo member.
///
diff --git a/clang/lib/Lex/Lexer.cpp b/clang/lib/Lex/Lexer.cpp
index 2797212c229f5..ccbc981cad84f 100644
--- a/clang/lib/Lex/Lexer.cpp
+++ b/clang/lib/Lex/Lexer.cpp
@@ -1182,7 +1182,7 @@ StringRef Lexer::getImmediateMacroNameForDiagnostics(
}
bool Lexer::isAsciiIdentifierContinueChar(char c, const LangOptions &LangOpts) {
- return isAsciiIdentifierContinue(c, LangOpts.DollarIdents);
+ return isAsciiIdentifierContinue(c, true);
}
bool Lexer::isNewLineEscaped(const char *BufferStart, const char *Str) {
@@ -1633,7 +1633,7 @@ static bool isAllowedIDChar(uint32_t C, const LangOptions &LangOpts,
bool &IsExtension) {
if (LangOpts.AsmPreprocessor) {
return false;
- } else if (LangOpts.DollarIdents && '$' == C) {
+ } else if ('$' == C) {
return true;
} else if (LangOpts.CPlusPlus || LangOpts.C23) {
// A non-leading codepoint must have the XID_Continue property.
@@ -2005,8 +2005,9 @@ fastParseASCIIIdentifier(const char *CurPtr,
return CurPtr;
}
-bool Lexer::LexIdentifierContinue(Token &Result, const char *CurPtr) {
- // Match [_A-Za-z0-9]*, we have already matched an identifier start.
+bool Lexer::LexIdentifierContinue(Token &Result, const char *CurPtr,
+ bool HasDollar) {
+ // Match [_A-Za-z0-9$]*, we have already matched an identifier start.
while (true) {
@@ -2020,12 +2021,10 @@ bool Lexer::LexIdentifierContinue(Token &Result, const char *CurPtr) {
continue;
}
if (C == '$') {
- // If we hit a $ and they are not supported in identifiers, we are done.
- if (!LangOpts.DollarIdents)
- break;
- // Otherwise, emit a diagnostic and continue.
if (!isLexingRawMode())
Diag(CurPtr, diag::ext_dollar_in_identifier);
+
+ HasDollar = true;
CurPtr = ConsumeChar(CurPtr, Size, Result);
continue;
}
@@ -2048,10 +2047,13 @@ bool Lexer::LexIdentifierContinue(Token &Result, const char *CurPtr) {
// Fill in Result.IdentifierInfo and update the token kind,
// looking up the identifier in the identifier table.
- const IdentifierInfo *II = PP->LookUpIdentifierInfo(Result);
+ IdentifierInfo *II = PP->LookUpIdentifierInfo(Result);
// Note that we have to call PP->LookUpIdentifierInfo() even for code
// completion, it writes IdentifierInfo into Result, and callers rely on it.
+ if (HasDollar)
+ II->setDollarIdentifier(true);
+
// If the completion point is at the end of an identifier, we want to treat
// the identifier as incomplete even if it resolves to a macro or a keyword.
// This allows e.g. 'class^' to complete to 'classifier'.
@@ -4084,16 +4086,12 @@ bool Lexer::LexTokenInternal(Token &Result) {
MIOpt.ReadToken();
return LexIdentifierContinue(Result, CurPtr);
case '$': // $ in identifiers.
- if (LangOpts.DollarIdents) {
- if (!isLexingRawMode())
- Diag(CurPtr-1, diag::ext_dollar_in_identifier);
- // Notify MIOpt that we read a non-whitespace/non-comment token.
- MIOpt.ReadToken();
- return LexIdentifierContinue(Result, CurPtr);
- }
+ if (!isLexingRawMode())
+ Diag(CurPtr - 1, diag::ext_dollar_in_identifier);
- Kind = tok::unknown;
- break;
+ // Notify MIOpt that we read a non-whitespace/non-comment token.
+ MIOpt.ReadToken();
+ return LexIdentifierContinue(Result, CurPtr, true);
// C99 6.4.4: Character Constants.
case '\'':
diff --git a/clang/lib/Lex/Preprocessor.cpp b/clang/lib/Lex/Preprocessor.cpp
index 1e21b4a94cea3..62c24f0cc0232 100644
--- a/clang/lib/Lex/Preprocessor.cpp
+++ b/clang/lib/Lex/Preprocessor.cpp
@@ -822,6 +822,22 @@ void Preprocessor::updateOutOfDateIdentifier(const IdentifierInfo &II) const {
getExternalSource()->updateOutOfDateIdentifier(II);
}
+bool Preprocessor::HandleDollarIdentifier(Token &Identifier) {
+ // skip validation in macros
+ if (InMacroArgs || (CurLexer && (CurLexer->ParsingPreprocessorDirective ||
+ CurLexer->isLexingRawMode())))
+ return true;
+
+ IdentifierInfo *II = Identifier.getIdentifierInfo();
+
+ // Emit error for $identifiers in configurations that do not allow them to
+ // persist after phase 6
+ if (II && II->isDollarIdentifier() && !getLangOpts().DollarIdents)
+ Diag(Identifier, diag::err_dollar_in_identifier) << II->getName();
+
+ return true;
+}
+
/// HandleIdentifier - This callback is invoked when the lexer reads an
/// identifier. This callback looks up the identifier in the map and/or
/// potentially macro expands it or turns it into a named token (like 'for').
@@ -870,7 +886,8 @@ bool Preprocessor::HandleIdentifier(Token &Identifier) {
// C99 6.10.3p10: If the preprocessing token immediately after the
// macro name isn't a '(', this macro should not be expanded.
if (!MI->isFunctionLike() || isNextPPTokenOneOf(tok::l_paren))
- return HandleMacroExpandedIdentifier(Identifier, MD);
+ return HandleMacroExpandedIdentifier(Identifier, MD) &&
+ HandleDollarIdentifier(Identifier);
} else {
// C99 6.10.3.4p2 says that a disabled macro may never again be
// expanded, even if it's in a context where it could be expanded in the
@@ -917,7 +934,7 @@ bool Preprocessor::HandleIdentifier(Token &Identifier) {
return hadModuleLoaderFatalFailure();
}
- return true;
+ return HandleDollarIdentifier(Identifier);
}
void Preprocessor::Lex(Token &Result) {
diff --git a/clang/test/Lexer/dollar-macros.cpp b/clang/test/Lexer/dollar-macros.cpp
new file mode 100644
index 0000000000000..cd91815d409ba
--- /dev/null
+++ b/clang/test/Lexer/dollar-macros.cpp
@@ -0,0 +1,27 @@
+// RUN: %clang_cc1 %s -verify -fsyntax-only -fno-dollar-idents
+
+#define f(x) #x
+#define g(x) f(x)
+#define foo bar
+
+constexpr auto expanded = g($foo);
+static_assert(expanded[0] == '$'
+ && expanded[1] == 'f'
+ && expanded[2] == 'o'
+ && expanded[3] == 'o');
+
+#define $test 1
+int a = $test;
+
+int $b = 2; // expected-error {{identifier '$b' is not supported with the current configuration}}
+
+#define name $name
+int name = 2;
+// expected-error at -1 {{identifier '$name' is not supported with the current configuration}}
+
+int $zoinks() { // expected-error {{identifier '$zoinks' is not supported with the current configuration}}
+ return $y + name;
+ // expected-error at -1 {{identifier '$y' is not supported with the current configuration}} \
+ // expected-error at -1 {{use of undeclared identifier '$y'}} \
+ // expected-error at -1 {{identifier '$name' is not supported with the current configuration}}
+}
>From 05dbdd6c4e0bbe23d3178037befbbaf05fbc7697 Mon Sep 17 00:00:00 2001
From: Matthias Wippich <mfwippich at gmail.com>
Date: Mon, 25 May 2026 23:13:08 +0200
Subject: [PATCH 2/9] add option for old behavior
---
clang/include/clang/Basic/LangOptions.def | 1 +
clang/include/clang/Options/Options.td | 5 +++++
clang/lib/Driver/ToolChains/Clang.cpp | 2 ++
clang/lib/Lex/Lexer.cpp | 13 +++++++++++--
clang/test/Lexer/dollar-macros.cpp | 2 +-
5 files changed, 20 insertions(+), 3 deletions(-)
diff --git a/clang/include/clang/Basic/LangOptions.def b/clang/include/clang/Basic/LangOptions.def
index 4a3e3b7c04822..59bef7daa330a 100644
--- a/clang/include/clang/Basic/LangOptions.def
+++ b/clang/include/clang/Basic/LangOptions.def
@@ -76,6 +76,7 @@ LANGOPT(Char8 , 1, 0, NotCompatible, "char8_t keyword")
LANGOPT(IEEE128 , 1, 0, NotCompatible, "__ieee128 keyword")
LANGOPT(DeclSpecKeyword , 1, 0, NotCompatible, "__declspec keyword")
LANGOPT(DollarIdents , 1, 1, Benign, "'$' in identifiers")
+LANGOPT(DollarMacros , 1, 1, Benign, "'$' in macros")
LANGOPT(AsmPreprocessor , 1, 0, Benign, "preprocessor in asm mode")
LANGOPT(GNUMode , 1, 1, NotCompatible, "GNU extensions")
LANGOPT(GNUKeywords , 1, 1, NotCompatible, "GNU keywords")
diff --git a/clang/include/clang/Options/Options.td b/clang/include/clang/Options/Options.td
index 025e8e7d7d761..78b736a59cd75 100644
--- a/clang/include/clang/Options/Options.td
+++ b/clang/include/clang/Options/Options.td
@@ -2274,6 +2274,11 @@ defm dollars_in_identifiers : BoolFOption<"dollars-in-identifiers",
PosFlag<SetTrue, [], [ClangOption], "Allow">,
NegFlag<SetFalse, [], [ClangOption], "Disallow">,
BothFlags<[], [ClangOption, CC1Option], " '$' in identifiers">>;
+defm dollars_in_macros : BoolFOption<"dollars-in-macros",
+ LangOpts<"DollarMacros">, DefaultTrue,
+ PosFlag<SetTrue, [], [CC1Option], "Allow">,
+ NegFlag<SetFalse, [], [CC1Option], "Disallow">,
+ BothFlags<[], [CC1Option], " '$' in macros">>;
defm dwarf2_cfi_asm
: BoolFOption<"dwarf2-cfi-asm", CodeGenOpts<"Dwarf2CFIAsm">, DefaultFalse,
diff --git a/clang/lib/Driver/ToolChains/Clang.cpp b/clang/lib/Driver/ToolChains/Clang.cpp
index 7657afb14f077..de8e89ca0e4e3 100644
--- a/clang/lib/Driver/ToolChains/Clang.cpp
+++ b/clang/lib/Driver/ToolChains/Clang.cpp
@@ -7855,6 +7855,8 @@ void Clang::ConstructJob(Compilation &C, const JobAction &JA,
CmdArgs.push_back("-fno-dollars-in-identifiers");
}
+
+
Args.addOptInFlag(CmdArgs, options::OPT_fapple_pragma_pack,
options::OPT_fno_apple_pragma_pack);
diff --git a/clang/lib/Lex/Lexer.cpp b/clang/lib/Lex/Lexer.cpp
index ccbc981cad84f..b0266f21ade02 100644
--- a/clang/lib/Lex/Lexer.cpp
+++ b/clang/lib/Lex/Lexer.cpp
@@ -1182,7 +1182,7 @@ StringRef Lexer::getImmediateMacroNameForDiagnostics(
}
bool Lexer::isAsciiIdentifierContinueChar(char c, const LangOptions &LangOpts) {
- return isAsciiIdentifierContinue(c, true);
+ return isAsciiIdentifierContinue(c, LangOpts.DollarMacros);
}
bool Lexer::isNewLineEscaped(const char *BufferStart, const char *Str) {
@@ -1633,7 +1633,7 @@ static bool isAllowedIDChar(uint32_t C, const LangOptions &LangOpts,
bool &IsExtension) {
if (LangOpts.AsmPreprocessor) {
return false;
- } else if ('$' == C) {
+ } else if (LangOpts.DollarMacros && '$' == C) {
return true;
} else if (LangOpts.CPlusPlus || LangOpts.C23) {
// A non-leading codepoint must have the XID_Continue property.
@@ -2021,6 +2021,10 @@ bool Lexer::LexIdentifierContinue(Token &Result, const char *CurPtr,
continue;
}
if (C == '$') {
+ // If we hit a $ and they are not supported in macros, we are done.
+ if (!LangOpts.DollarMacros)
+ break;
+ // Otherwise, emit a diagnostic and continue.
if (!isLexingRawMode())
Diag(CurPtr, diag::ext_dollar_in_identifier);
@@ -4086,6 +4090,11 @@ bool Lexer::LexTokenInternal(Token &Result) {
MIOpt.ReadToken();
return LexIdentifierContinue(Result, CurPtr);
case '$': // $ in identifiers.
+ if (!LangOpts.DollarMacros) {
+ Kind = tok::unknown;
+ break;
+ }
+
if (!isLexingRawMode())
Diag(CurPtr - 1, diag::ext_dollar_in_identifier);
diff --git a/clang/test/Lexer/dollar-macros.cpp b/clang/test/Lexer/dollar-macros.cpp
index cd91815d409ba..6ed042fbdc719 100644
--- a/clang/test/Lexer/dollar-macros.cpp
+++ b/clang/test/Lexer/dollar-macros.cpp
@@ -1,4 +1,4 @@
-// RUN: %clang_cc1 %s -verify -fsyntax-only -fno-dollar-idents
+// RUN: %clang_cc1 %s -verify -fsyntax-only -fno-dollars-in-identifiers
#define f(x) #x
#define g(x) f(x)
>From 8d26f31924a7ad024569637c19784c4e2f178673 Mon Sep 17 00:00:00 2001
From: Matthias Wippich <mfwippich at gmail.com>
Date: Sat, 30 May 2026 23:23:53 +0200
Subject: [PATCH 3/9] add release note
---
clang/docs/ReleaseNotes.rst | 22 ++++++++++++++++++++++
1 file changed, 22 insertions(+)
diff --git a/clang/docs/ReleaseNotes.rst b/clang/docs/ReleaseNotes.rst
index fc0a1d2d4c926..953a0a9f9e072 100644
--- a/clang/docs/ReleaseNotes.rst
+++ b/clang/docs/ReleaseNotes.rst
@@ -71,6 +71,28 @@ C/C++ Language Potentially Breaking Changes
Clang would previously ``break`` out of the ``while`` loop, whereas GCC (since version 9) would
``break`` out of the ``for`` loop here. Now, Clang and GCC both break out of the ``for`` loop.
+ - Clang now allows `$` to appear in identifiers during preprocessing, even when they are not
+ otherwise supported in identifiers (e.g. when compiling with ``-fno-dollars-in-identifiers``).
+
+ Previously preprocessing behavior was depending on whether `$` is supported in identifiers or not.
+ This changed whether a `$` was parsed as (part of) an identifier token or a separate token.
+
+ For example consider:
+
+ .. code-block:: c++
+
+ #define f(x) #x
+ #define g(x) f(x)
+ #define foo bar
+ g($foo)
+
+ Before this change, preprocessing beavior would silently change - if `$` is allowed in identifiers,
+ the code above would expand to `"$foo"` and `"$bar"` otherwise. Now, it will always expand to `"$foo"`,
+ regardless of support for `$` in identifiers.
+
+ The previous behavior can be restored by passing the option ``-fno-dollars-in-macros`` to the clang frontend (in
+ conjunction with ``-fno-dollars-in-identifiers``).
+
C++ Specific Potentially Breaking Changes
-----------------------------------------
>From 7c88a53b72d47cd0e40d4ee1768dca80a4a47434 Mon Sep 17 00:00:00 2001
From: Matthias Wippich <mfwippich at gmail.com>
Date: Sun, 31 May 2026 01:39:21 +0200
Subject: [PATCH 4/9] fix formatting
---
clang/lib/Driver/ToolChains/Clang.cpp | 2 --
clang/lib/Lex/Lexer.cpp | 2 +-
2 files changed, 1 insertion(+), 3 deletions(-)
diff --git a/clang/lib/Driver/ToolChains/Clang.cpp b/clang/lib/Driver/ToolChains/Clang.cpp
index de8e89ca0e4e3..7657afb14f077 100644
--- a/clang/lib/Driver/ToolChains/Clang.cpp
+++ b/clang/lib/Driver/ToolChains/Clang.cpp
@@ -7855,8 +7855,6 @@ void Clang::ConstructJob(Compilation &C, const JobAction &JA,
CmdArgs.push_back("-fno-dollars-in-identifiers");
}
-
-
Args.addOptInFlag(CmdArgs, options::OPT_fapple_pragma_pack,
options::OPT_fno_apple_pragma_pack);
diff --git a/clang/lib/Lex/Lexer.cpp b/clang/lib/Lex/Lexer.cpp
index b0266f21ade02..57f4b4807076d 100644
--- a/clang/lib/Lex/Lexer.cpp
+++ b/clang/lib/Lex/Lexer.cpp
@@ -2023,7 +2023,7 @@ bool Lexer::LexIdentifierContinue(Token &Result, const char *CurPtr,
if (C == '$') {
// If we hit a $ and they are not supported in macros, we are done.
if (!LangOpts.DollarMacros)
- break;
+ break;
// Otherwise, emit a diagnostic and continue.
if (!isLexingRawMode())
Diag(CurPtr, diag::ext_dollar_in_identifier);
>From a2d3f4ea0a982d759ce9d3e53a5259efc7047617 Mon Sep 17 00:00:00 2001
From: Matthias Wippich <mfwippich at gmail.com>
Date: Sun, 31 May 2026 01:49:49 +0200
Subject: [PATCH 5/9] fix release note
---
clang/docs/ReleaseNotes.rst | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/clang/docs/ReleaseNotes.rst b/clang/docs/ReleaseNotes.rst
index 953a0a9f9e072..1c19085c64a8a 100644
--- a/clang/docs/ReleaseNotes.rst
+++ b/clang/docs/ReleaseNotes.rst
@@ -71,7 +71,7 @@ C/C++ Language Potentially Breaking Changes
Clang would previously ``break`` out of the ``while`` loop, whereas GCC (since version 9) would
``break`` out of the ``for`` loop here. Now, Clang and GCC both break out of the ``for`` loop.
- - Clang now allows `$` to appear in identifiers during preprocessing, even when they are not
+- Clang now allows `$` to appear in identifiers during preprocessing, even when they are not
otherwise supported in identifiers (e.g. when compiling with ``-fno-dollars-in-identifiers``).
Previously preprocessing behavior was depending on whether `$` is supported in identifiers or not.
>From fd23187d4d85a59bc150d2f7c57cfa2a8985e816 Mon Sep 17 00:00:00 2001
From: Matthias Wippich <mfwippich at gmail.com>
Date: Thu, 4 Jun 2026 18:04:07 +0200
Subject: [PATCH 6/9] fix ice
---
clang/lib/Lex/Preprocessor.cpp | 3 +++
1 file changed, 3 insertions(+)
diff --git a/clang/lib/Lex/Preprocessor.cpp b/clang/lib/Lex/Preprocessor.cpp
index 62c24f0cc0232..4057600e6a0aa 100644
--- a/clang/lib/Lex/Preprocessor.cpp
+++ b/clang/lib/Lex/Preprocessor.cpp
@@ -828,6 +828,9 @@ bool Preprocessor::HandleDollarIdentifier(Token &Identifier) {
CurLexer->isLexingRawMode())))
return true;
+ if (Identifier.isAnnotation())
+ return true;
+
IdentifierInfo *II = Identifier.getIdentifierInfo();
// Emit error for $identifiers in configurations that do not allow them to
>From 094bdf3fbbb8ea20b4692f7f4f08d4d761d80b48 Mon Sep 17 00:00:00 2001
From: Matthias Wippich <mfwippich at gmail.com>
Date: Thu, 4 Jun 2026 22:48:00 +0200
Subject: [PATCH 7/9] restore old behavior for asm preprocessing
---
clang/include/clang/Options/Options.td | 2 +-
clang/test/Preprocessor/assembler-with-cpp.c | 2 +-
clang/unittests/Lex/LexerTest.cpp | 6 +++---
3 files changed, 5 insertions(+), 5 deletions(-)
diff --git a/clang/include/clang/Options/Options.td b/clang/include/clang/Options/Options.td
index 78b736a59cd75..bd39503b7d9fc 100644
--- a/clang/include/clang/Options/Options.td
+++ b/clang/include/clang/Options/Options.td
@@ -2275,7 +2275,7 @@ defm dollars_in_identifiers : BoolFOption<"dollars-in-identifiers",
NegFlag<SetFalse, [], [ClangOption], "Disallow">,
BothFlags<[], [ClangOption, CC1Option], " '$' in identifiers">>;
defm dollars_in_macros : BoolFOption<"dollars-in-macros",
- LangOpts<"DollarMacros">, DefaultTrue,
+ LangOpts<"DollarMacros">, Default<!strconcat("!", asm_preprocessor.KeyPath)>,
PosFlag<SetTrue, [], [CC1Option], "Allow">,
NegFlag<SetFalse, [], [CC1Option], "Disallow">,
BothFlags<[], [CC1Option], " '$' in macros">>;
diff --git a/clang/test/Preprocessor/assembler-with-cpp.c b/clang/test/Preprocessor/assembler-with-cpp.c
index d128968a96d67..c7700d2e5bdad 100644
--- a/clang/test/Preprocessor/assembler-with-cpp.c
+++ b/clang/test/Preprocessor/assembler-with-cpp.c
@@ -47,7 +47,7 @@
6: FOO(blarg)
// CHECK-Identifiers-False: 6: blarg $foo
-// RUN: %clang_cc1 -x assembler-with-cpp -fdollars-in-identifiers -E %s -o - | FileCheck -check-prefix=CHECK-Identifiers-True -strict-whitespace %s
+// RUN: %clang_cc1 -x assembler-with-cpp -fdollars-in-macros -fdollars-in-identifiers -E %s -o - | FileCheck -check-prefix=CHECK-Identifiers-True -strict-whitespace %s
#define FOO(name) name ## $foo
7: FOO(blarg)
// CHECK-Identifiers-True: 7: blarg$foo
diff --git a/clang/unittests/Lex/LexerTest.cpp b/clang/unittests/Lex/LexerTest.cpp
index eaac861fa5e2c..2327b6ce59712 100644
--- a/clang/unittests/Lex/LexerTest.cpp
+++ b/clang/unittests/Lex/LexerTest.cpp
@@ -881,10 +881,10 @@ TEST_F(LexerTest, FindEndOfIdentifierContinuation) {
EXPECT_EQ(Measure("naïve", 2), 4u); // 'ï' (2 bytes) + "ve".
EXPECT_EQ(Measure("æon", 0), 4u); // Starts with 'æ' (2 bytes).
- // Dollar sign (requires DollarIdents).
- LangOpts.DollarIdents = true;
+ // Dollar sign (requires DollarMacros).
+ LangOpts.DollarMacros = true;
EXPECT_EQ(Measure("ab$cd", 2), 3u); // '$' is identifier continue.
- LangOpts.DollarIdents = false;
+ LangOpts.DollarMacros = false;
EXPECT_EQ(Measure("ab$cd", 2), 0u); // '$' is not identifier continue.
}
>From 554917459f11e00352863188c90d1121f7d79991 Mon Sep 17 00:00:00 2001
From: Matthias Wippich <mfwippich at gmail.com>
Date: Fri, 5 Jun 2026 02:34:44 +0200
Subject: [PATCH 8/9] make -fno-dollars-in-macros have no effect when
-fdollars-in-identifiers is enabled, add tests for all flag combinations
---
clang/lib/Lex/Lexer.cpp | 4 ++--
clang/test/Lexer/dollar-macros.cpp | 27 ++++++++++++++++++---------
clang/unittests/Lex/LexerTest.cpp | 4 +++-
3 files changed, 23 insertions(+), 12 deletions(-)
diff --git a/clang/lib/Lex/Lexer.cpp b/clang/lib/Lex/Lexer.cpp
index 57f4b4807076d..1ada364dfae3b 100644
--- a/clang/lib/Lex/Lexer.cpp
+++ b/clang/lib/Lex/Lexer.cpp
@@ -2022,7 +2022,7 @@ bool Lexer::LexIdentifierContinue(Token &Result, const char *CurPtr,
}
if (C == '$') {
// If we hit a $ and they are not supported in macros, we are done.
- if (!LangOpts.DollarMacros)
+ if (!LangOpts.DollarMacros && !LangOpts.DollarIdents)
break;
// Otherwise, emit a diagnostic and continue.
if (!isLexingRawMode())
@@ -4090,7 +4090,7 @@ bool Lexer::LexTokenInternal(Token &Result) {
MIOpt.ReadToken();
return LexIdentifierContinue(Result, CurPtr);
case '$': // $ in identifiers.
- if (!LangOpts.DollarMacros) {
+ if (!LangOpts.DollarMacros && !LangOpts.DollarIdents) {
Kind = tok::unknown;
break;
}
diff --git a/clang/test/Lexer/dollar-macros.cpp b/clang/test/Lexer/dollar-macros.cpp
index 6ed042fbdc719..4a60a41a12acc 100644
--- a/clang/test/Lexer/dollar-macros.cpp
+++ b/clang/test/Lexer/dollar-macros.cpp
@@ -1,4 +1,7 @@
-// RUN: %clang_cc1 %s -verify -fsyntax-only -fno-dollars-in-identifiers
+// RUN: %clang_cc1 %s -fsyntax-only -fno-dollars-in-identifiers -fdollars-in-macros -verify=expected
+// RUN: %clang_cc1 %s -fsyntax-only -fno-dollars-in-identifiers -fno-dollars-in-macros -verify=old
+// RUN: %clang_cc1 %s -fsyntax-only -fdollars-in-identifiers -fno-dollars-in-macros
+// RUN: %clang_cc1 %s -fsyntax-only -fdollars-in-identifiers -fdollars-in-macros
#define f(x) #x
#define g(x) f(x)
@@ -9,19 +12,25 @@ static_assert(expanded[0] == '$'
&& expanded[1] == 'f'
&& expanded[2] == 'o'
&& expanded[3] == 'o');
+// old-error at -3 {{static assertion failed due to requirement 'expanded[1] == 'f''}} \
+// old-note at -3 {{expression evaluates to ''b' (0x62, 98) == 'f' (0x66, 102)'}}
-#define $test 1
-int a = $test;
+#define $test 1 // old-error {{macro name must be an identifier}}
+int a = $test; // old-error {{expected expression}}
-int $b = 2; // expected-error {{identifier '$b' is not supported with the current configuration}}
+int $b = 2;
+// expected-error at -1 {{identifier '$b' is not supported with the current configuration}} \
+// old-error at -1 {{expected unqualified-id}}
#define name $name
int name = 2;
-// expected-error at -1 {{identifier '$name' is not supported with the current configuration}}
+// expected-error at -1 {{identifier '$name' is not supported with the current configuration}} \
+// old-error at -1 {{expected unqualified-id}}
-int $zoinks() { // expected-error {{identifier '$zoinks' is not supported with the current configuration}}
- return $y + name;
- // expected-error at -1 {{identifier '$y' is not supported with the current configuration}} \
- // expected-error at -1 {{use of undeclared identifier '$y'}} \
+int $zoinks() {
+// expected-error at -1 {{identifier '$zoinks' is not supported with the current configuration}} \
+// old-error at -1 {{expected unqualified-id}}
+ return $b + name;
+ // expected-error at -1 {{identifier '$b' is not supported with the current configuration}} \
// expected-error at -1 {{identifier '$name' is not supported with the current configuration}}
}
diff --git a/clang/unittests/Lex/LexerTest.cpp b/clang/unittests/Lex/LexerTest.cpp
index 2327b6ce59712..46a21bc81d2b7 100644
--- a/clang/unittests/Lex/LexerTest.cpp
+++ b/clang/unittests/Lex/LexerTest.cpp
@@ -881,9 +881,11 @@ TEST_F(LexerTest, FindEndOfIdentifierContinuation) {
EXPECT_EQ(Measure("naïve", 2), 4u); // 'ï' (2 bytes) + "ve".
EXPECT_EQ(Measure("æon", 0), 4u); // Starts with 'æ' (2 bytes).
- // Dollar sign (requires DollarMacros).
+ // Dollar sign (requires DollarIdents or DollarMacros).
+ LangOpts.DollarIdents = true;
LangOpts.DollarMacros = true;
EXPECT_EQ(Measure("ab$cd", 2), 3u); // '$' is identifier continue.
+ LangOpts.DollarIdents = false;
LangOpts.DollarMacros = false;
EXPECT_EQ(Measure("ab$cd", 2), 0u); // '$' is not identifier continue.
}
>From 336dcf271faf744b19e7e389b13bba64cdfb0779 Mon Sep 17 00:00:00 2001
From: Matthias Wippich <mfwippich at gmail.com>
Date: Fri, 5 Jun 2026 02:50:51 +0200
Subject: [PATCH 9/9] make isAllowedIDChar respect LangOpts.DollarIdents
---
clang/lib/Lex/Lexer.cpp | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/clang/lib/Lex/Lexer.cpp b/clang/lib/Lex/Lexer.cpp
index 1ada364dfae3b..2505369737d7f 100644
--- a/clang/lib/Lex/Lexer.cpp
+++ b/clang/lib/Lex/Lexer.cpp
@@ -1633,7 +1633,7 @@ static bool isAllowedIDChar(uint32_t C, const LangOptions &LangOpts,
bool &IsExtension) {
if (LangOpts.AsmPreprocessor) {
return false;
- } else if (LangOpts.DollarMacros && '$' == C) {
+ } else if ((LangOpts.DollarMacros || LangOpts.DollarIdents) && '$' == C) {
return true;
} else if (LangOpts.CPlusPlus || LangOpts.C23) {
// A non-leading codepoint must have the XID_Continue property.
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