[clang][clang-cl] Add -fms-preprocessor-compat and support /Zc:preprocessor #167200
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This adds a new compiler flag called -fms-preprocessor-compat which may be used to control whether the preprocessor enables full compatibility mode, which was previously rolled into -fms-compatibility. This means that /Zc:preprocessor for clang-cl can be implemented as an alias for -fno-preprocessor-compat. This diverges from MSVC in that using C11 or newer will not automatically use the conforming preprocessor. Additionally, there is currently not a way to opt out of the charize operator and the /##/ trick when using just the light -fms-extensions. Opting out of the non-conforming preprocessor while using -fms-compatibility will match MSVC in that those two extensions are disabled.
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@llvm/pr-subscribers-clang-driver Author: Josh Dowell (Slartibarty) ChangesThis adds a new compiler flag called This can be merged as-is, but I would greatly appreciate feedback on this from those more experienced with working with the Clang frontend, specifically regarding the following points: Under MSVC, There is currently not a way to opt-out of the two preprocessor extensions enabled by Fixes #147304 Full diff: https://github.com/llvm/llvm-project/pull/167200.diff 14 Files Affected:
diff --git a/clang/docs/ReleaseNotes.rst b/clang/docs/ReleaseNotes.rst
index 3a4e1fce2511e..a0db2a8794e14 100644
--- a/clang/docs/ReleaseNotes.rst
+++ b/clang/docs/ReleaseNotes.rst
@@ -306,12 +306,17 @@ Non-comprehensive list of changes in this release
- Clang now rejects the invalid use of ``constexpr`` with ``auto`` and an explicit type in C. (#GH163090)
+- ``_MSVC_TRADITIONAL`` is now defined to ``0`` when using ``-fms-extensions``. The charize operator and ``/##/`` paste trick remain as supported extensions, which is a divergence from MSVC.
+
New Compiler Flags
------------------
- New option ``-fno-sanitize-debug-trap-reasons`` added to disable emitting trap reasons into the debug info when compiling with trapping UBSan (e.g. ``-fsanitize-trap=undefined``).
- New option ``-fsanitize-debug-trap-reasons=`` added to control emitting trap reasons into the debug info when compiling with trapping UBSan (e.g. ``-fsanitize-trap=undefined``).
- New options for enabling allocation token instrumentation: ``-fsanitize=alloc-token``, ``-falloc-token-max=``, ``-fsanitize-alloc-token-fast-abi``, ``-fsanitize-alloc-token-extended``.
- The ``-resource-dir`` option is now displayed in the list of options shown by ``--help``.
+- The ``-fms-preprocessor-compat`` flag has been added to control whether full emulation of the MSVC traditional preprocessor is performed.
+ Using ``-fms-preprocessor-compat`` will define ``_MSVC_TRADITIONAL`` to ``1``, and enables the full set of functionality required to emulate
+ the old MSVC character buffer based preprocessor as closely as possible. It is enabled by default when using ``-fms-compatibility``, which is the case for clang-cl.
Lanai Support
^^^^^^^^^^^^^^
@@ -581,6 +586,8 @@ Android Support
Windows Support
^^^^^^^^^^^^^^^
+- clang-cl now supports ``/Zc:preprocessor``, which is an alias for ``-fno-ms-preprocessor-compat``.
+
LoongArch Support
^^^^^^^^^^^^^^^^^
- Enable linker relaxation by default for loongarch64.
diff --git a/clang/docs/UsersManual.rst b/clang/docs/UsersManual.rst
index fb22ad3c90af4..2d5208ed317e9 100644
--- a/clang/docs/UsersManual.rst
+++ b/clang/docs/UsersManual.rst
@@ -5055,6 +5055,8 @@ Execute ``clang-cl /?`` to see a list of supported options:
/Zc:trigraphs Enable trigraphs
/Zc:twoPhase- Disable two-phase name lookup in templates
/Zc:twoPhase Enable two-phase name lookup in templates
+ /Zc:preprocessor- Use the traditional (non-conforming) preprocessor (default)
+ /Zc:preprocessor Use the standard conforming preprocessor
/Zi Alias for /Z7. Does not produce PDBs.
/Zl Don't mention any default libraries in the object file
/Zp Set the default maximum struct packing alignment to 1
diff --git a/clang/include/clang/Basic/LangOptions.def b/clang/include/clang/Basic/LangOptions.def
index 40fc66ea12e34..33dc642f7a280 100644
--- a/clang/include/clang/Basic/LangOptions.def
+++ b/clang/include/clang/Basic/LangOptions.def
@@ -269,6 +269,7 @@ LANGOPT(HIPStdParInterposeAlloc, 1, 0, NotCompatible, "Replace allocations / dea
LANGOPT(OpenACC , 1, 0, NotCompatible, "OpenACC Enabled")
+LANGOPT(MSVCPreprocessor , 1, 0, NotCompatible, "Fully emulate the Microsoft Visual C++ traditional (non-conforming) preprocessor")
LANGOPT(MSVCEnableStdcMacro , 1, 0, NotCompatible, "Define __STDC__ with '-fms-compatibility'")
LANGOPT(SizedDeallocation , 1, 0, NotCompatible, "sized deallocation")
LANGOPT(AlignedAllocation , 1, 0, NotCompatible, "aligned allocation")
diff --git a/clang/include/clang/Basic/LangOptions.h b/clang/include/clang/Basic/LangOptions.h
index 8aa89d8c8c807..02d958878088f 100644
--- a/clang/include/clang/Basic/LangOptions.h
+++ b/clang/include/clang/Basic/LangOptions.h
@@ -627,6 +627,26 @@ class LangOptions : public LangOptionsBase {
return MSCompatibilityVersion >= MajorVersion * 100000U;
}
+ /// Returns true if we want to enable lightweight Microsoft preprocessor
+ /// extensions.
+ /// Historically, MicrosoftExt and MSVCCompat enabled different extensions
+ /// to the preprocessor, but we want to disable a majority of them when
+ /// MSVCPreprocessor is set to false.
+ bool wantsMSVCPreprocessorExtensions() const {
+ // If we want full compatibility then we need the extensions
+ if (MSVCPreprocessor)
+ return true;
+ // If MS extensions are turned off, we don't want the extensions
+ if (!MicrosoftExt)
+ return false;
+ // If we're in full MSVC compat mode, we know MSVCPreprocessor is false,
+ // thus, we don't want the extensions
+ if (MSVCCompat)
+ return false;
+ // We just want lightweight extensions
+ return true;
+ }
+
bool isOverflowPatternExcluded(OverflowPatternExclusionKind Kind) const {
if (OverflowPatternExclusionMask & OverflowPatternExclusionKind::None)
return false;
diff --git a/clang/include/clang/Driver/Options.td b/clang/include/clang/Driver/Options.td
index 11e81e032d5fc..795b1d4cbf9f1 100644
--- a/clang/include/clang/Driver/Options.td
+++ b/clang/include/clang/Driver/Options.td
@@ -3238,6 +3238,10 @@ def fms_compatibility : Flag<["-"], "fms-compatibility">, Group<f_Group>,
Visibility<[ClangOption, CC1Option, CLOption]>,
HelpText<"Enable full Microsoft Visual C++ compatibility">,
MarshallingInfoFlag<LangOpts<"MSVCCompat">>;
+def fms_preprocessor_compat : Flag<["-"], "fms-preprocessor-compat">, Group<f_Group>,
+ Visibility<[ClangOption, CC1Option]>,
+ HelpText<"Enable full emulation of the traditional MSVC preprocesor">,
+ MarshallingInfoFlag<LangOpts<"MSVCPreprocessor">>;
def fms_define_stdc : Flag<["-"], "fms-define-stdc">, Group<f_Group>,
Visibility<[ClangOption, CC1Option, CLOption]>,
HelpText<"Define '__STDC__' to '1' in MSVC Compatibility mode">,
@@ -3614,6 +3618,8 @@ def fno_ms_extensions : Flag<["-"], "fno-ms-extensions">, Group<f_Group>,
Visibility<[ClangOption, CLOption]>;
def fno_ms_compatibility : Flag<["-"], "fno-ms-compatibility">, Group<f_Group>,
Visibility<[ClangOption, CLOption]>;
+def fno_ms_preprocessor_compat : Flag<["-"], "fno-ms-preprocessor-compat">, Group<f_Group>,
+ Visibility<[ClangOption]>;
def fno_objc_legacy_dispatch : Flag<["-"], "fno-objc-legacy-dispatch">, Group<f_Group>;
def fno_objc_weak : Flag<["-"], "fno-objc-weak">, Group<f_Group>,
Visibility<[ClangOption, CC1Option]>;
@@ -9123,6 +9129,12 @@ def _SLASH_vd : CLJoined<"vd">, HelpText<"Control vtordisp placement">,
Alias<vtordisp_mode_EQ>;
def _SLASH_X : CLFlag<"X">,
HelpText<"Do not add %INCLUDE% to include search path">, Alias<nostdlibinc>;
+def _SLASH_Zc_preprocessor : CLFlag<"Zc:preprocessor">,
+ HelpText<"Use the standard conforming preprocessor">,
+ Alias<fno_ms_preprocessor_compat>;
+def _SLASH_Zc_preprocessor_ : CLFlag<"Zc:preprocessor-">,
+ HelpText<"Use the traditional (non-conforming) preprocessor (default)">,
+ Alias<fms_preprocessor_compat>;
def _SLASH_Zc___STDC__ : CLFlag<"Zc:__STDC__">,
HelpText<"Define __STDC__">,
Alias<fms_define_stdc>;
diff --git a/clang/lib/Driver/ToolChains/Clang.cpp b/clang/lib/Driver/ToolChains/Clang.cpp
index 30d3e5293a31b..dd32c0bd92b7e 100644
--- a/clang/lib/Driver/ToolChains/Clang.cpp
+++ b/clang/lib/Driver/ToolChains/Clang.cpp
@@ -7056,6 +7056,10 @@ void Clang::ConstructJob(Compilation &C, const JobAction &JA,
if (!types::isCXX(Input.getType()) &&
Args.hasArg(options::OPT_fms_define_stdc))
CmdArgs.push_back("-fms-define-stdc");
+ // FIXME: This should be disabled by default in C11 and newer.
+ if (Args.hasFlag(options::OPT_fms_preprocessor_compat,
+ options::OPT_fno_ms_preprocessor_compat, true))
+ CmdArgs.push_back("-fms-preprocessor-compat");
}
if (Triple.isWindowsMSVCEnvironment() && !D.IsCLMode() &&
diff --git a/clang/lib/Frontend/InitPreprocessor.cpp b/clang/lib/Frontend/InitPreprocessor.cpp
index b88d9f89c5f71..d9571c57cfe86 100644
--- a/clang/lib/Frontend/InitPreprocessor.cpp
+++ b/clang/lib/Frontend/InitPreprocessor.cpp
@@ -1022,6 +1022,17 @@ static void InitializePredefinedMacros(const TargetInfo &TI,
}
}
+ if (LangOpts.MSVCPreprocessor) {
+ Builder.defineMacro("_MSVC_TRADITIONAL", "1");
+ } else if (LangOpts.MicrosoftExt) {
+ // Note: when set to 0 this macro implies, under cl.exe, that the
+ // charize operator and /##/ no longer function as they used to.
+ // However, we have special code that cleanly deals with these patterns,
+ // so we'll allow them to exist as extensions, even though we are stating
+ // that we do not support the "traditional" preprocessor.
+ Builder.defineMacro("_MSVC_TRADITIONAL", "0");
+ }
+
// Macros to help identify the narrow and wide character sets
// FIXME: clang currently ignores -fexec-charset=. If this changes,
// then this may need to be updated.
diff --git a/clang/lib/Lex/Lexer.cpp b/clang/lib/Lex/Lexer.cpp
index b282a600c0e56..94bb5a8446e55 100644
--- a/clang/lib/Lex/Lexer.cpp
+++ b/clang/lib/Lex/Lexer.cpp
@@ -2181,7 +2181,7 @@ const char *Lexer::LexUDSuffix(Token &Result, const char *CurPtr,
if (!IsUDSuffix) {
if (!isLexingRawMode())
- Diag(CurPtr, LangOpts.MSVCCompat
+ Diag(CurPtr, LangOpts.MSVCPreprocessor
? diag::ext_ms_reserved_user_defined_literal
: diag::ext_reserved_user_defined_literal)
<< FixItHint::CreateInsertion(getSourceLocation(CurPtr), " ");
@@ -4217,7 +4217,7 @@ bool Lexer::LexTokenInternal(Token &Result, bool TokAtPhysicalStartOfLine) {
Kind = tok::hashhash; // '%:%:' -> '##'
CurPtr = ConsumeChar(ConsumeChar(CurPtr, SizeTmp, Result),
SizeTmp2, Result);
- } else if (Char == '@' && LangOpts.MicrosoftExt) {// %:@ -> #@ -> Charize
+ } else if (Char == '@' && LangOpts.wantsMSVCPreprocessorExtensions()) {// %:@ -> #@ -> Charize
CurPtr = ConsumeChar(CurPtr, SizeTmp, Result);
if (!isLexingRawMode())
Diag(BufferPtr, diag::ext_charize_microsoft);
@@ -4405,7 +4405,7 @@ bool Lexer::LexTokenInternal(Token &Result, bool TokAtPhysicalStartOfLine) {
if (Char == '#') {
Kind = tok::hashhash;
CurPtr = ConsumeChar(CurPtr, SizeTmp, Result);
- } else if (Char == '@' && LangOpts.MicrosoftExt) { // #@ -> Charize
+ } else if (Char == '@' && LangOpts.wantsMSVCPreprocessorExtensions()) { // #@ -> Charize
Kind = tok::hashat;
if (!isLexingRawMode())
Diag(BufferPtr, diag::ext_charize_microsoft);
diff --git a/clang/lib/Lex/TokenLexer.cpp b/clang/lib/Lex/TokenLexer.cpp
index 47f4134fb1465..cbe6ba1d56e1f 100644
--- a/clang/lib/Lex/TokenLexer.cpp
+++ b/clang/lib/Lex/TokenLexer.cpp
@@ -145,7 +145,7 @@ bool TokenLexer::MaybeRemoveCommaBeforeVaArgs(
// In Microsoft-compatibility mode, a comma is removed in the expansion
// of " ... , __VA_ARGS__ " if __VA_ARGS__ is empty. This extension is
// not supported by gcc.
- if (!HasPasteOperator && !PP.getLangOpts().MSVCCompat)
+ if (!HasPasteOperator && !PP.getLangOpts().MSVCPreprocessor)
return false;
// GCC removes the comma in the expansion of " ... , ## __VA_ARGS__ " if
@@ -467,7 +467,7 @@ void TokenLexer::ExpandFunctionArguments() {
// behavior by not considering single commas from nested macro
// expansions as argument separators. Set a flag on the token so we can
// test for this later when the macro expansion is processed.
- if (PP.getLangOpts().MSVCCompat && NumToks == 1 &&
+ if (PP.getLangOpts().MSVCPreprocessor && NumToks == 1 &&
ResultToks.back().is(tok::comma))
ResultToks.back().setFlag(Token::IgnoredComma);
@@ -653,7 +653,7 @@ bool TokenLexer::Lex(Token &Tok) {
// Special processing of L#x macros in -fms-compatibility mode.
// Microsoft compiler is able to form a wide string literal from
// 'L#macro_arg' construct in a function-like macro.
- (PP.getLangOpts().MSVCCompat &&
+ (PP.getLangOpts().MSVCPreprocessor &&
isWideStringLiteralFromMacro(Tok, Tokens[CurTokenIdx])))) {
// When handling the microsoft /##/ extension, the final token is
// returned by pasteTokens, not the pasted token.
@@ -732,7 +732,7 @@ bool TokenLexer::pasteTokens(Token &LHSTok, ArrayRef<Token> TokenStream,
unsigned int &CurIdx) {
assert(CurIdx > 0 && "## can not be the first token within tokens");
assert((TokenStream[CurIdx].is(tok::hashhash) ||
- (PP.getLangOpts().MSVCCompat &&
+ (PP.getLangOpts().MSVCPreprocessor &&
isWideStringLiteralFromMacro(LHSTok, TokenStream[CurIdx]))) &&
"Token at this Index must be ## or part of the MSVC 'L "
"#macro-arg' pasting pair");
@@ -740,7 +740,7 @@ bool TokenLexer::pasteTokens(Token &LHSTok, ArrayRef<Token> TokenStream,
// MSVC: If previous token was pasted, this must be a recovery from an invalid
// paste operation. Ignore spaces before this token to mimic MSVC output.
// Required for generating valid UUID strings in some MS headers.
- if (PP.getLangOpts().MicrosoftExt && (CurIdx >= 2) &&
+ if (PP.getLangOpts().wantsMSVCPreprocessorExtensions() && (CurIdx >= 2) &&
TokenStream[CurIdx - 2].is(tok::hashhash))
LHSTok.clearFlag(Token::LeadingSpace);
@@ -854,8 +854,8 @@ bool TokenLexer::pasteTokens(Token &LHSTok, ArrayRef<Token> TokenStream,
// Test for the Microsoft extension of /##/ turning into // here on the
// error path.
- if (PP.getLangOpts().MicrosoftExt && LHSTok.is(tok::slash) &&
- RHS.is(tok::slash)) {
+ if (PP.getLangOpts().wantsMSVCPreprocessorExtensions() &&
+ LHSTok.is(tok::slash) && RHS.is(tok::slash)) {
HandleMicrosoftCommentPaste(LHSTok, Loc);
return true;
}
diff --git a/clang/test/Driver/cl-options.c b/clang/test/Driver/cl-options.c
index 1b1169b71554a..fb137d48c0fe8 100644
--- a/clang/test/Driver/cl-options.c
+++ b/clang/test/Driver/cl-options.c
@@ -375,6 +375,12 @@
// RUN: %clang_cl -c -### /std:clatest -- %s 2>&1 | FileCheck -check-prefix CHECK-CLATEST %s
// CHECK-CLATEST: -std=c23
+// RUN: %clang_cl -c -### /Zc:preprocessor- -- %s 2>&1 | FileCheck -check-prefix CHECK-ZC-PREPROCESSOR-NO %s
+// CHECK-ZC-PREPROCESSOR-NO: -fms-preprocessor-compat
+
+// RUN: %clang_cl -c -### /Zc:preprocessor -- %s 2>&1 | FileCheck -check-prefix CHECK-ZC-PREPROCESSOR %s
+// CHECK-ZC-PREPROCESSOR-NOT: -fms-preprocessor-compat
+
// For some warning ids, we can map from MSVC warning to Clang warning.
// RUN: %clang_cl -wd4005 -wd4100 -wd4910 -wd4996 -wd12345678 -### -- %s 2>&1 | FileCheck -check-prefix=Wno %s
// Wno: "-cc1"
diff --git a/clang/test/Lexer/ms-compatibility.c b/clang/test/Lexer/ms-compatibility.c
index 2981b8e062e93..ebaf89a7c4738 100644
--- a/clang/test/Lexer/ms-compatibility.c
+++ b/clang/test/Lexer/ms-compatibility.c
@@ -1,4 +1,4 @@
-// RUN: %clang_cc1 -E -fms-compatibility %s | FileCheck --check-prefix=CHECK-MS-COMPAT %s
+// RUN: %clang_cc1 -E -fms-preprocessor-compat %s | FileCheck --check-prefix=CHECK-MS-COMPAT %s
// RUN: %clang_cc1 -E %s | FileCheck --check-prefix=CHECK-NO-MS-COMPAT %s
#define FN(x) L#x
diff --git a/clang/test/Preprocessor/macro_fn_comma_swallow2.c b/clang/test/Preprocessor/macro_fn_comma_swallow2.c
index 93ab2b83664a1..f594e4139bb33 100644
--- a/clang/test/Preprocessor/macro_fn_comma_swallow2.c
+++ b/clang/test/Preprocessor/macro_fn_comma_swallow2.c
@@ -5,7 +5,7 @@
// RUN: %clang_cc1 -E -std=c11 %s | FileCheck -check-prefix=C99 -strict-whitespace %s
// RUN: %clang_cc1 -E -x c++ %s | FileCheck -check-prefix=GCC -strict-whitespace %s
// RUN: %clang_cc1 -E -std=gnu99 %s | FileCheck -check-prefix=GCC -strict-whitespace %s
-// RUN: %clang_cc1 -E -fms-compatibility %s | FileCheck -check-prefix=MS -strict-whitespace %s
+// RUN: %clang_cc1 -E -fms-preprocessor-compat %s | FileCheck -check-prefix=MS -strict-whitespace %s
// RUN: %clang_cc1 -E -DNAMED %s | FileCheck -check-prefix=GCC -strict-whitespace %s
// RUN: %clang_cc1 -E -std=c99 -DNAMED %s | FileCheck -check-prefix=C99 -strict-whitespace %s
diff --git a/clang/test/Preprocessor/microsoft-ext.c b/clang/test/Preprocessor/microsoft-ext.c
index aae52a84b62f1..51e2f9aff234d 100644
--- a/clang/test/Preprocessor/microsoft-ext.c
+++ b/clang/test/Preprocessor/microsoft-ext.c
@@ -1,4 +1,4 @@
-// RUN: %clang_cc1 -E -fms-compatibility %s -o %t
+// RUN: %clang_cc1 -E -fms-preprocessor-compat %s -o %t
// RUN: FileCheck %s < %t
# define M2(x, y) x + y
diff --git a/clang/test/Preprocessor/microsoft-preprocessor-compat.c b/clang/test/Preprocessor/microsoft-preprocessor-compat.c
new file mode 100644
index 0000000000000..29883409a85b8
--- /dev/null
+++ b/clang/test/Preprocessor/microsoft-preprocessor-compat.c
@@ -0,0 +1,36 @@
+// This test verifies that _MSVC_TRADITIONAL is defined under the right
+// circumstances, microsoft-ext.c is responsible for testing the implementation
+// details of the traditional preprocessor.
+// FIXME: C11 should eventually use the conforming preprocessor by default.
+//
+// RUN: %clang_cc1 -E %s | FileCheck --check-prefix=CHECK-DEFAULT %s
+// RUN: %clang_cc1 -E -fms-extensions %s | FileCheck --check-prefix=CHECK-MS-EXT %s
+// RUN: %clang -E -fms-compatibility %s | FileCheck --check-prefix=CHECK-MS-COMPAT %s
+// RUN: %clang_cc1 -E -fms-preprocessor-compat %s | FileCheck --check-prefix=CHECK-MS-PREPRO-COMPAT %s
+// RUN: %clang_cl -E %s | FileCheck --check-prefix=CHECK-CL %s
+// RUN: %clang_cl -E /std:c11 %s | FileCheck --check-prefix=CHECK-C11 %s
+// RUN: %clang_cl -E /Zc:preprocessor %s | FileCheck --check-prefix=CHECK-ZC-PREPRO %s
+// RUN: %clang_cl -E /clang:-fno-ms-preprocessor-compat %s | FileCheck --check-prefix=CHECK-NO-PREPRO-COMPAT %s
+
+typedef enum {
+ NOT_DEFINED,
+ IS_ZERO,
+ IS_ONE
+} State;
+
+#if !defined(_MSVC_TRADITIONAL)
+State state = NOT_DEFINED;
+#elif _MSVC_TRADITIONAL == 0
+State state = IS_ZERO;
+#elif _MSVC_TRADITIONAL == 1
+State state = IS_ONE;
+#endif
+
+// CHECK-DEFAULT: State state = NOT_DEFINED;
+// CHECK-MS-EXT: State state = IS_ZERO;
+// CHECK-MS-COMPAT: State state = IS_ONE;
+// CHECK-MS-PREPRO-COMPAT: State state = IS_ONE;
+// CHECK-CL: State state = IS_ONE;
+// CHECK-C11: State state = IS_ONE;
+// CHECK-ZC-PREPRO: State state = IS_ZERO;
+// CHECK-NO-PREPRO-COMPAT: State state = IS_ZERO;
|
Member
|
@llvm/pr-subscribers-clang Author: Josh Dowell (Slartibarty) ChangesThis adds a new compiler flag called This can be merged as-is, but I would greatly appreciate feedback on this from those more experienced with working with the Clang frontend, specifically regarding the following points: Under MSVC, There is currently not a way to opt-out of the two preprocessor extensions enabled by Fixes #147304 Full diff: https://github.com/llvm/llvm-project/pull/167200.diff 14 Files Affected:
diff --git a/clang/docs/ReleaseNotes.rst b/clang/docs/ReleaseNotes.rst
index 3a4e1fce2511e..a0db2a8794e14 100644
--- a/clang/docs/ReleaseNotes.rst
+++ b/clang/docs/ReleaseNotes.rst
@@ -306,12 +306,17 @@ Non-comprehensive list of changes in this release
- Clang now rejects the invalid use of ``constexpr`` with ``auto`` and an explicit type in C. (#GH163090)
+- ``_MSVC_TRADITIONAL`` is now defined to ``0`` when using ``-fms-extensions``. The charize operator and ``/##/`` paste trick remain as supported extensions, which is a divergence from MSVC.
+
New Compiler Flags
------------------
- New option ``-fno-sanitize-debug-trap-reasons`` added to disable emitting trap reasons into the debug info when compiling with trapping UBSan (e.g. ``-fsanitize-trap=undefined``).
- New option ``-fsanitize-debug-trap-reasons=`` added to control emitting trap reasons into the debug info when compiling with trapping UBSan (e.g. ``-fsanitize-trap=undefined``).
- New options for enabling allocation token instrumentation: ``-fsanitize=alloc-token``, ``-falloc-token-max=``, ``-fsanitize-alloc-token-fast-abi``, ``-fsanitize-alloc-token-extended``.
- The ``-resource-dir`` option is now displayed in the list of options shown by ``--help``.
+- The ``-fms-preprocessor-compat`` flag has been added to control whether full emulation of the MSVC traditional preprocessor is performed.
+ Using ``-fms-preprocessor-compat`` will define ``_MSVC_TRADITIONAL`` to ``1``, and enables the full set of functionality required to emulate
+ the old MSVC character buffer based preprocessor as closely as possible. It is enabled by default when using ``-fms-compatibility``, which is the case for clang-cl.
Lanai Support
^^^^^^^^^^^^^^
@@ -581,6 +586,8 @@ Android Support
Windows Support
^^^^^^^^^^^^^^^
+- clang-cl now supports ``/Zc:preprocessor``, which is an alias for ``-fno-ms-preprocessor-compat``.
+
LoongArch Support
^^^^^^^^^^^^^^^^^
- Enable linker relaxation by default for loongarch64.
diff --git a/clang/docs/UsersManual.rst b/clang/docs/UsersManual.rst
index fb22ad3c90af4..2d5208ed317e9 100644
--- a/clang/docs/UsersManual.rst
+++ b/clang/docs/UsersManual.rst
@@ -5055,6 +5055,8 @@ Execute ``clang-cl /?`` to see a list of supported options:
/Zc:trigraphs Enable trigraphs
/Zc:twoPhase- Disable two-phase name lookup in templates
/Zc:twoPhase Enable two-phase name lookup in templates
+ /Zc:preprocessor- Use the traditional (non-conforming) preprocessor (default)
+ /Zc:preprocessor Use the standard conforming preprocessor
/Zi Alias for /Z7. Does not produce PDBs.
/Zl Don't mention any default libraries in the object file
/Zp Set the default maximum struct packing alignment to 1
diff --git a/clang/include/clang/Basic/LangOptions.def b/clang/include/clang/Basic/LangOptions.def
index 40fc66ea12e34..33dc642f7a280 100644
--- a/clang/include/clang/Basic/LangOptions.def
+++ b/clang/include/clang/Basic/LangOptions.def
@@ -269,6 +269,7 @@ LANGOPT(HIPStdParInterposeAlloc, 1, 0, NotCompatible, "Replace allocations / dea
LANGOPT(OpenACC , 1, 0, NotCompatible, "OpenACC Enabled")
+LANGOPT(MSVCPreprocessor , 1, 0, NotCompatible, "Fully emulate the Microsoft Visual C++ traditional (non-conforming) preprocessor")
LANGOPT(MSVCEnableStdcMacro , 1, 0, NotCompatible, "Define __STDC__ with '-fms-compatibility'")
LANGOPT(SizedDeallocation , 1, 0, NotCompatible, "sized deallocation")
LANGOPT(AlignedAllocation , 1, 0, NotCompatible, "aligned allocation")
diff --git a/clang/include/clang/Basic/LangOptions.h b/clang/include/clang/Basic/LangOptions.h
index 8aa89d8c8c807..02d958878088f 100644
--- a/clang/include/clang/Basic/LangOptions.h
+++ b/clang/include/clang/Basic/LangOptions.h
@@ -627,6 +627,26 @@ class LangOptions : public LangOptionsBase {
return MSCompatibilityVersion >= MajorVersion * 100000U;
}
+ /// Returns true if we want to enable lightweight Microsoft preprocessor
+ /// extensions.
+ /// Historically, MicrosoftExt and MSVCCompat enabled different extensions
+ /// to the preprocessor, but we want to disable a majority of them when
+ /// MSVCPreprocessor is set to false.
+ bool wantsMSVCPreprocessorExtensions() const {
+ // If we want full compatibility then we need the extensions
+ if (MSVCPreprocessor)
+ return true;
+ // If MS extensions are turned off, we don't want the extensions
+ if (!MicrosoftExt)
+ return false;
+ // If we're in full MSVC compat mode, we know MSVCPreprocessor is false,
+ // thus, we don't want the extensions
+ if (MSVCCompat)
+ return false;
+ // We just want lightweight extensions
+ return true;
+ }
+
bool isOverflowPatternExcluded(OverflowPatternExclusionKind Kind) const {
if (OverflowPatternExclusionMask & OverflowPatternExclusionKind::None)
return false;
diff --git a/clang/include/clang/Driver/Options.td b/clang/include/clang/Driver/Options.td
index 11e81e032d5fc..795b1d4cbf9f1 100644
--- a/clang/include/clang/Driver/Options.td
+++ b/clang/include/clang/Driver/Options.td
@@ -3238,6 +3238,10 @@ def fms_compatibility : Flag<["-"], "fms-compatibility">, Group<f_Group>,
Visibility<[ClangOption, CC1Option, CLOption]>,
HelpText<"Enable full Microsoft Visual C++ compatibility">,
MarshallingInfoFlag<LangOpts<"MSVCCompat">>;
+def fms_preprocessor_compat : Flag<["-"], "fms-preprocessor-compat">, Group<f_Group>,
+ Visibility<[ClangOption, CC1Option]>,
+ HelpText<"Enable full emulation of the traditional MSVC preprocesor">,
+ MarshallingInfoFlag<LangOpts<"MSVCPreprocessor">>;
def fms_define_stdc : Flag<["-"], "fms-define-stdc">, Group<f_Group>,
Visibility<[ClangOption, CC1Option, CLOption]>,
HelpText<"Define '__STDC__' to '1' in MSVC Compatibility mode">,
@@ -3614,6 +3618,8 @@ def fno_ms_extensions : Flag<["-"], "fno-ms-extensions">, Group<f_Group>,
Visibility<[ClangOption, CLOption]>;
def fno_ms_compatibility : Flag<["-"], "fno-ms-compatibility">, Group<f_Group>,
Visibility<[ClangOption, CLOption]>;
+def fno_ms_preprocessor_compat : Flag<["-"], "fno-ms-preprocessor-compat">, Group<f_Group>,
+ Visibility<[ClangOption]>;
def fno_objc_legacy_dispatch : Flag<["-"], "fno-objc-legacy-dispatch">, Group<f_Group>;
def fno_objc_weak : Flag<["-"], "fno-objc-weak">, Group<f_Group>,
Visibility<[ClangOption, CC1Option]>;
@@ -9123,6 +9129,12 @@ def _SLASH_vd : CLJoined<"vd">, HelpText<"Control vtordisp placement">,
Alias<vtordisp_mode_EQ>;
def _SLASH_X : CLFlag<"X">,
HelpText<"Do not add %INCLUDE% to include search path">, Alias<nostdlibinc>;
+def _SLASH_Zc_preprocessor : CLFlag<"Zc:preprocessor">,
+ HelpText<"Use the standard conforming preprocessor">,
+ Alias<fno_ms_preprocessor_compat>;
+def _SLASH_Zc_preprocessor_ : CLFlag<"Zc:preprocessor-">,
+ HelpText<"Use the traditional (non-conforming) preprocessor (default)">,
+ Alias<fms_preprocessor_compat>;
def _SLASH_Zc___STDC__ : CLFlag<"Zc:__STDC__">,
HelpText<"Define __STDC__">,
Alias<fms_define_stdc>;
diff --git a/clang/lib/Driver/ToolChains/Clang.cpp b/clang/lib/Driver/ToolChains/Clang.cpp
index 30d3e5293a31b..dd32c0bd92b7e 100644
--- a/clang/lib/Driver/ToolChains/Clang.cpp
+++ b/clang/lib/Driver/ToolChains/Clang.cpp
@@ -7056,6 +7056,10 @@ void Clang::ConstructJob(Compilation &C, const JobAction &JA,
if (!types::isCXX(Input.getType()) &&
Args.hasArg(options::OPT_fms_define_stdc))
CmdArgs.push_back("-fms-define-stdc");
+ // FIXME: This should be disabled by default in C11 and newer.
+ if (Args.hasFlag(options::OPT_fms_preprocessor_compat,
+ options::OPT_fno_ms_preprocessor_compat, true))
+ CmdArgs.push_back("-fms-preprocessor-compat");
}
if (Triple.isWindowsMSVCEnvironment() && !D.IsCLMode() &&
diff --git a/clang/lib/Frontend/InitPreprocessor.cpp b/clang/lib/Frontend/InitPreprocessor.cpp
index b88d9f89c5f71..d9571c57cfe86 100644
--- a/clang/lib/Frontend/InitPreprocessor.cpp
+++ b/clang/lib/Frontend/InitPreprocessor.cpp
@@ -1022,6 +1022,17 @@ static void InitializePredefinedMacros(const TargetInfo &TI,
}
}
+ if (LangOpts.MSVCPreprocessor) {
+ Builder.defineMacro("_MSVC_TRADITIONAL", "1");
+ } else if (LangOpts.MicrosoftExt) {
+ // Note: when set to 0 this macro implies, under cl.exe, that the
+ // charize operator and /##/ no longer function as they used to.
+ // However, we have special code that cleanly deals with these patterns,
+ // so we'll allow them to exist as extensions, even though we are stating
+ // that we do not support the "traditional" preprocessor.
+ Builder.defineMacro("_MSVC_TRADITIONAL", "0");
+ }
+
// Macros to help identify the narrow and wide character sets
// FIXME: clang currently ignores -fexec-charset=. If this changes,
// then this may need to be updated.
diff --git a/clang/lib/Lex/Lexer.cpp b/clang/lib/Lex/Lexer.cpp
index b282a600c0e56..94bb5a8446e55 100644
--- a/clang/lib/Lex/Lexer.cpp
+++ b/clang/lib/Lex/Lexer.cpp
@@ -2181,7 +2181,7 @@ const char *Lexer::LexUDSuffix(Token &Result, const char *CurPtr,
if (!IsUDSuffix) {
if (!isLexingRawMode())
- Diag(CurPtr, LangOpts.MSVCCompat
+ Diag(CurPtr, LangOpts.MSVCPreprocessor
? diag::ext_ms_reserved_user_defined_literal
: diag::ext_reserved_user_defined_literal)
<< FixItHint::CreateInsertion(getSourceLocation(CurPtr), " ");
@@ -4217,7 +4217,7 @@ bool Lexer::LexTokenInternal(Token &Result, bool TokAtPhysicalStartOfLine) {
Kind = tok::hashhash; // '%:%:' -> '##'
CurPtr = ConsumeChar(ConsumeChar(CurPtr, SizeTmp, Result),
SizeTmp2, Result);
- } else if (Char == '@' && LangOpts.MicrosoftExt) {// %:@ -> #@ -> Charize
+ } else if (Char == '@' && LangOpts.wantsMSVCPreprocessorExtensions()) {// %:@ -> #@ -> Charize
CurPtr = ConsumeChar(CurPtr, SizeTmp, Result);
if (!isLexingRawMode())
Diag(BufferPtr, diag::ext_charize_microsoft);
@@ -4405,7 +4405,7 @@ bool Lexer::LexTokenInternal(Token &Result, bool TokAtPhysicalStartOfLine) {
if (Char == '#') {
Kind = tok::hashhash;
CurPtr = ConsumeChar(CurPtr, SizeTmp, Result);
- } else if (Char == '@' && LangOpts.MicrosoftExt) { // #@ -> Charize
+ } else if (Char == '@' && LangOpts.wantsMSVCPreprocessorExtensions()) { // #@ -> Charize
Kind = tok::hashat;
if (!isLexingRawMode())
Diag(BufferPtr, diag::ext_charize_microsoft);
diff --git a/clang/lib/Lex/TokenLexer.cpp b/clang/lib/Lex/TokenLexer.cpp
index 47f4134fb1465..cbe6ba1d56e1f 100644
--- a/clang/lib/Lex/TokenLexer.cpp
+++ b/clang/lib/Lex/TokenLexer.cpp
@@ -145,7 +145,7 @@ bool TokenLexer::MaybeRemoveCommaBeforeVaArgs(
// In Microsoft-compatibility mode, a comma is removed in the expansion
// of " ... , __VA_ARGS__ " if __VA_ARGS__ is empty. This extension is
// not supported by gcc.
- if (!HasPasteOperator && !PP.getLangOpts().MSVCCompat)
+ if (!HasPasteOperator && !PP.getLangOpts().MSVCPreprocessor)
return false;
// GCC removes the comma in the expansion of " ... , ## __VA_ARGS__ " if
@@ -467,7 +467,7 @@ void TokenLexer::ExpandFunctionArguments() {
// behavior by not considering single commas from nested macro
// expansions as argument separators. Set a flag on the token so we can
// test for this later when the macro expansion is processed.
- if (PP.getLangOpts().MSVCCompat && NumToks == 1 &&
+ if (PP.getLangOpts().MSVCPreprocessor && NumToks == 1 &&
ResultToks.back().is(tok::comma))
ResultToks.back().setFlag(Token::IgnoredComma);
@@ -653,7 +653,7 @@ bool TokenLexer::Lex(Token &Tok) {
// Special processing of L#x macros in -fms-compatibility mode.
// Microsoft compiler is able to form a wide string literal from
// 'L#macro_arg' construct in a function-like macro.
- (PP.getLangOpts().MSVCCompat &&
+ (PP.getLangOpts().MSVCPreprocessor &&
isWideStringLiteralFromMacro(Tok, Tokens[CurTokenIdx])))) {
// When handling the microsoft /##/ extension, the final token is
// returned by pasteTokens, not the pasted token.
@@ -732,7 +732,7 @@ bool TokenLexer::pasteTokens(Token &LHSTok, ArrayRef<Token> TokenStream,
unsigned int &CurIdx) {
assert(CurIdx > 0 && "## can not be the first token within tokens");
assert((TokenStream[CurIdx].is(tok::hashhash) ||
- (PP.getLangOpts().MSVCCompat &&
+ (PP.getLangOpts().MSVCPreprocessor &&
isWideStringLiteralFromMacro(LHSTok, TokenStream[CurIdx]))) &&
"Token at this Index must be ## or part of the MSVC 'L "
"#macro-arg' pasting pair");
@@ -740,7 +740,7 @@ bool TokenLexer::pasteTokens(Token &LHSTok, ArrayRef<Token> TokenStream,
// MSVC: If previous token was pasted, this must be a recovery from an invalid
// paste operation. Ignore spaces before this token to mimic MSVC output.
// Required for generating valid UUID strings in some MS headers.
- if (PP.getLangOpts().MicrosoftExt && (CurIdx >= 2) &&
+ if (PP.getLangOpts().wantsMSVCPreprocessorExtensions() && (CurIdx >= 2) &&
TokenStream[CurIdx - 2].is(tok::hashhash))
LHSTok.clearFlag(Token::LeadingSpace);
@@ -854,8 +854,8 @@ bool TokenLexer::pasteTokens(Token &LHSTok, ArrayRef<Token> TokenStream,
// Test for the Microsoft extension of /##/ turning into // here on the
// error path.
- if (PP.getLangOpts().MicrosoftExt && LHSTok.is(tok::slash) &&
- RHS.is(tok::slash)) {
+ if (PP.getLangOpts().wantsMSVCPreprocessorExtensions() &&
+ LHSTok.is(tok::slash) && RHS.is(tok::slash)) {
HandleMicrosoftCommentPaste(LHSTok, Loc);
return true;
}
diff --git a/clang/test/Driver/cl-options.c b/clang/test/Driver/cl-options.c
index 1b1169b71554a..fb137d48c0fe8 100644
--- a/clang/test/Driver/cl-options.c
+++ b/clang/test/Driver/cl-options.c
@@ -375,6 +375,12 @@
// RUN: %clang_cl -c -### /std:clatest -- %s 2>&1 | FileCheck -check-prefix CHECK-CLATEST %s
// CHECK-CLATEST: -std=c23
+// RUN: %clang_cl -c -### /Zc:preprocessor- -- %s 2>&1 | FileCheck -check-prefix CHECK-ZC-PREPROCESSOR-NO %s
+// CHECK-ZC-PREPROCESSOR-NO: -fms-preprocessor-compat
+
+// RUN: %clang_cl -c -### /Zc:preprocessor -- %s 2>&1 | FileCheck -check-prefix CHECK-ZC-PREPROCESSOR %s
+// CHECK-ZC-PREPROCESSOR-NOT: -fms-preprocessor-compat
+
// For some warning ids, we can map from MSVC warning to Clang warning.
// RUN: %clang_cl -wd4005 -wd4100 -wd4910 -wd4996 -wd12345678 -### -- %s 2>&1 | FileCheck -check-prefix=Wno %s
// Wno: "-cc1"
diff --git a/clang/test/Lexer/ms-compatibility.c b/clang/test/Lexer/ms-compatibility.c
index 2981b8e062e93..ebaf89a7c4738 100644
--- a/clang/test/Lexer/ms-compatibility.c
+++ b/clang/test/Lexer/ms-compatibility.c
@@ -1,4 +1,4 @@
-// RUN: %clang_cc1 -E -fms-compatibility %s | FileCheck --check-prefix=CHECK-MS-COMPAT %s
+// RUN: %clang_cc1 -E -fms-preprocessor-compat %s | FileCheck --check-prefix=CHECK-MS-COMPAT %s
// RUN: %clang_cc1 -E %s | FileCheck --check-prefix=CHECK-NO-MS-COMPAT %s
#define FN(x) L#x
diff --git a/clang/test/Preprocessor/macro_fn_comma_swallow2.c b/clang/test/Preprocessor/macro_fn_comma_swallow2.c
index 93ab2b83664a1..f594e4139bb33 100644
--- a/clang/test/Preprocessor/macro_fn_comma_swallow2.c
+++ b/clang/test/Preprocessor/macro_fn_comma_swallow2.c
@@ -5,7 +5,7 @@
// RUN: %clang_cc1 -E -std=c11 %s | FileCheck -check-prefix=C99 -strict-whitespace %s
// RUN: %clang_cc1 -E -x c++ %s | FileCheck -check-prefix=GCC -strict-whitespace %s
// RUN: %clang_cc1 -E -std=gnu99 %s | FileCheck -check-prefix=GCC -strict-whitespace %s
-// RUN: %clang_cc1 -E -fms-compatibility %s | FileCheck -check-prefix=MS -strict-whitespace %s
+// RUN: %clang_cc1 -E -fms-preprocessor-compat %s | FileCheck -check-prefix=MS -strict-whitespace %s
// RUN: %clang_cc1 -E -DNAMED %s | FileCheck -check-prefix=GCC -strict-whitespace %s
// RUN: %clang_cc1 -E -std=c99 -DNAMED %s | FileCheck -check-prefix=C99 -strict-whitespace %s
diff --git a/clang/test/Preprocessor/microsoft-ext.c b/clang/test/Preprocessor/microsoft-ext.c
index aae52a84b62f1..51e2f9aff234d 100644
--- a/clang/test/Preprocessor/microsoft-ext.c
+++ b/clang/test/Preprocessor/microsoft-ext.c
@@ -1,4 +1,4 @@
-// RUN: %clang_cc1 -E -fms-compatibility %s -o %t
+// RUN: %clang_cc1 -E -fms-preprocessor-compat %s -o %t
// RUN: FileCheck %s < %t
# define M2(x, y) x + y
diff --git a/clang/test/Preprocessor/microsoft-preprocessor-compat.c b/clang/test/Preprocessor/microsoft-preprocessor-compat.c
new file mode 100644
index 0000000000000..29883409a85b8
--- /dev/null
+++ b/clang/test/Preprocessor/microsoft-preprocessor-compat.c
@@ -0,0 +1,36 @@
+// This test verifies that _MSVC_TRADITIONAL is defined under the right
+// circumstances, microsoft-ext.c is responsible for testing the implementation
+// details of the traditional preprocessor.
+// FIXME: C11 should eventually use the conforming preprocessor by default.
+//
+// RUN: %clang_cc1 -E %s | FileCheck --check-prefix=CHECK-DEFAULT %s
+// RUN: %clang_cc1 -E -fms-extensions %s | FileCheck --check-prefix=CHECK-MS-EXT %s
+// RUN: %clang -E -fms-compatibility %s | FileCheck --check-prefix=CHECK-MS-COMPAT %s
+// RUN: %clang_cc1 -E -fms-preprocessor-compat %s | FileCheck --check-prefix=CHECK-MS-PREPRO-COMPAT %s
+// RUN: %clang_cl -E %s | FileCheck --check-prefix=CHECK-CL %s
+// RUN: %clang_cl -E /std:c11 %s | FileCheck --check-prefix=CHECK-C11 %s
+// RUN: %clang_cl -E /Zc:preprocessor %s | FileCheck --check-prefix=CHECK-ZC-PREPRO %s
+// RUN: %clang_cl -E /clang:-fno-ms-preprocessor-compat %s | FileCheck --check-prefix=CHECK-NO-PREPRO-COMPAT %s
+
+typedef enum {
+ NOT_DEFINED,
+ IS_ZERO,
+ IS_ONE
+} State;
+
+#if !defined(_MSVC_TRADITIONAL)
+State state = NOT_DEFINED;
+#elif _MSVC_TRADITIONAL == 0
+State state = IS_ZERO;
+#elif _MSVC_TRADITIONAL == 1
+State state = IS_ONE;
+#endif
+
+// CHECK-DEFAULT: State state = NOT_DEFINED;
+// CHECK-MS-EXT: State state = IS_ZERO;
+// CHECK-MS-COMPAT: State state = IS_ONE;
+// CHECK-MS-PREPRO-COMPAT: State state = IS_ONE;
+// CHECK-CL: State state = IS_ONE;
+// CHECK-C11: State state = IS_ONE;
+// CHECK-ZC-PREPRO: State state = IS_ZERO;
+// CHECK-NO-PREPRO-COMPAT: State state = IS_ZERO;
|
Author
|
CC'ing @AaronBallman since he was active in the original issue report. I assume the auto-assigned labels will help other maintainers see this too. |
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This adds a new compiler flag called
-fms-preprocessor-compatwhich may be used to control whether the preprocessor enables full Microsoft compatibility mode, which was previously rolled into-fms-compatibility.This means that
/Zc:preprocessorfor clang-cl can be implemented as an alias for-fno-ms-preprocessor-compat.It also sets the predefined macro
_MSVC_TRADITIONALunder appropriate circumstances.This can be merged as-is, but I would greatly appreciate feedback on this from those more experienced with working with the Clang frontend, specifically regarding the following points:
Under MSVC,
/Zc:preprocessoris implied when using/std:c11or newer, however I did not implement this due to there not being a straightforward or future proof way to get the current C standard in use when determining arguments for the Clang driver, there is already code in place which checks for C++20 or newer in the same function, for something else, but it is hacky and checks for every possible combination of C++20 arguments, of which there are many more for C11 and newer. Is this an okay divergence?There is currently not a way to opt-out of the two preprocessor extensions enabled by
-fms-extensionsunless you have also specified-fms-compatibilityas well as-fno-ms-preprocessor-compat. I implemented it this way so that using clang-cl like MSVC will indeed match MSVC exactly, where the charize operator and /##/ trick are disabled. I could percieve a situtation where it would be desirable to continue using these extensions under clang-cl, but I preferred matching MSVC. Is this okay?Fixes #147304