[clang] [clang] Add /Zc:__STDC__ flag to clang-cl (PR #68690)
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cfe-commits at lists.llvm.org
Sun Oct 15 16:26:48 PDT 2023
https://github.com/xbjfk updated https://github.com/llvm/llvm-project/pull/68690
>From a89bee09fa7564f336886ff0eb76987b939c0c2c Mon Sep 17 00:00:00 2001
From: Reagan Bohan <xbjfk.github at gmail.com>
Date: Sun, 15 Oct 2023 23:26:02 +0000
Subject: [PATCH] [clang] Add /Zc:__STDC__ flag to clang-cl
This commit adds the /Zc:__STDC__ argument from MSVC, which defines __STDC__.
This means, alongside stronger feature parity with MSVC,
that things that rely on __STDC__, such as autoconf, can work.
---
clang/docs/ReleaseNotes.rst | 3 +++
clang/include/clang/Basic/LangOptions.def | 2 +-
clang/include/clang/Driver/Options.td | 7 +++++++
clang/lib/Driver/ToolChains/Clang.cpp | 9 ++++++++-
clang/lib/Frontend/InitPreprocessor.cpp | 3 ++-
clang/test/Driver/cl-zc.cpp | 9 +++++++++
clang/test/Driver/ms-define-stdc.c | 11 +++++++++++
7 files changed, 41 insertions(+), 3 deletions(-)
create mode 100644 clang/test/Driver/ms-define-stdc.c
diff --git a/clang/docs/ReleaseNotes.rst b/clang/docs/ReleaseNotes.rst
index 2d918967e7f0b02..1932ee0e0661f4e 100644
--- a/clang/docs/ReleaseNotes.rst
+++ b/clang/docs/ReleaseNotes.rst
@@ -184,6 +184,9 @@ New Compiler Flags
preserving ``#include`` directives for "system" headers instead of copying
the preprocessed text to the output. This can greatly reduce the size of the
preprocessed output, which can be helpful when trying to reduce a test case.
+* ``-fms-define-stdc`` and its clang-cl counterpart ``/Zc:__STDC__``.
+ Matches MSVC behaviour by defining ``__STDC__`` to ``1`` when
+ MSVC compatibility mode is used. It has no effect for C++ code.
Deprecated Compiler Flags
-------------------------
diff --git a/clang/include/clang/Basic/LangOptions.def b/clang/include/clang/Basic/LangOptions.def
index c0ea4ecb9806a5b..b170dbd35c7e783 100644
--- a/clang/include/clang/Basic/LangOptions.def
+++ b/clang/include/clang/Basic/LangOptions.def
@@ -282,7 +282,7 @@ LANGOPT(HIPUseNewLaunchAPI, 1, 0, "Use new kernel launching API for HIP")
LANGOPT(OffloadUniformBlock, 1, 0, "Assume that kernels are launched with uniform block sizes (default true for CUDA/HIP and false otherwise)")
LANGOPT(HIPStdPar, 1, 0, "Enable Standard Parallel Algorithm Acceleration for HIP (experimental)")
LANGOPT(HIPStdParInterposeAlloc, 1, 0, "Replace allocations / deallocations with HIP RT calls when Standard Parallel Algorithm Acceleration for HIP is enabled (Experimental)")
-
+LANGOPT(MSVCEnableStdcMacro , 1, 0, "Define __STDC__ with '-fms-compatability'")
LANGOPT(SizedDeallocation , 1, 0, "sized deallocation")
LANGOPT(AlignedAllocation , 1, 0, "aligned allocation")
LANGOPT(AlignedAllocationUnavailable, 1, 0, "aligned allocation functions are unavailable")
diff --git a/clang/include/clang/Driver/Options.td b/clang/include/clang/Driver/Options.td
index c272a7f1c398aa6..106a1de898764f3 100644
--- a/clang/include/clang/Driver/Options.td
+++ b/clang/include/clang/Driver/Options.td
@@ -2821,6 +2821,10 @@ 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_define_stdc : Flag<["-"], "fms-define-stdc">, Group<f_Group>,
+ Visibility<[ClangOption, CC1Option]>,
+ HelpText<"Define '__STDC__' to '1' in MSVC Compatibility mode">,
+ MarshallingInfoFlag<LangOpts<"MSVCEnableStdcMacro">>;
def fms_extensions : Flag<["-"], "fms-extensions">, Group<f_Group>,
Visibility<[ClangOption, CC1Option, CLOption]>,
HelpText<"Accept some non-standard constructs supported by the Microsoft compiler">,
@@ -7933,6 +7937,9 @@ 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___STDC__ : CLFlag<"Zc:__STDC__">,
+ HelpText<"Define __STDC__">,
+ Alias<fms_define_stdc>;
def _SLASH_Zc_sizedDealloc : CLFlag<"Zc:sizedDealloc">,
HelpText<"Enable C++14 sized global deallocation functions">,
Alias<fsized_deallocation>;
diff --git a/clang/lib/Driver/ToolChains/Clang.cpp b/clang/lib/Driver/ToolChains/Clang.cpp
index bfd6c5c2864abf7..6f10ecf9dcb3108 100644
--- a/clang/lib/Driver/ToolChains/Clang.cpp
+++ b/clang/lib/Driver/ToolChains/Clang.cpp
@@ -6744,8 +6744,12 @@ void Clang::ConstructJob(Compilation &C, const JobAction &JA,
options::OPT_fms_compatibility, options::OPT_fno_ms_compatibility,
(IsWindowsMSVC && Args.hasFlag(options::OPT_fms_extensions,
options::OPT_fno_ms_extensions, true)));
- if (IsMSVCCompat)
+ if (IsMSVCCompat) {
CmdArgs.push_back("-fms-compatibility");
+ if (!types::isCXX(Input.getType()) &&
+ Args.hasArg(options::OPT_fms_define_stdc))
+ CmdArgs.push_back("-fms-define-stdc");
+ }
if (Triple.isWindowsMSVCEnvironment() && !D.IsCLMode() &&
Args.hasArg(options::OPT_fms_runtime_lib_EQ))
@@ -7922,6 +7926,9 @@ void Clang::AddClangCLArgs(const ArgList &Args, types::ID InputType,
CmdArgs.push_back("-fno-wchar");
}
+ if (!types::isCXX(InputType) && Args.hasArg(options::OPT_fms_define_stdc))
+ CmdArgs.push_back("-fms-define-stdc");
+
if (Args.hasArg(options::OPT__SLASH_kernel)) {
llvm::Triple::ArchType Arch = getToolChain().getArch();
std::vector<std::string> Values =
diff --git a/clang/lib/Frontend/InitPreprocessor.cpp b/clang/lib/Frontend/InitPreprocessor.cpp
index 846e5fce6de7b2c..e7ce08a8766d80c 100644
--- a/clang/lib/Frontend/InitPreprocessor.cpp
+++ b/clang/lib/Frontend/InitPreprocessor.cpp
@@ -423,7 +423,8 @@ static void InitializeStandardPredefinedMacros(const TargetInfo &TI,
// [C++] Whether __STDC__ is predefined and if so, what its value is,
// are implementation-defined.
// (Removed in C++20.)
- if (!LangOpts.MSVCCompat && !LangOpts.TraditionalCPP)
+ if ((!LangOpts.MSVCCompat || LangOpts.MSVCEnableStdcMacro) &&
+ !LangOpts.TraditionalCPP)
Builder.defineMacro("__STDC__");
// -- __STDC_HOSTED__
// The integer literal 1 if the implementation is a hosted
diff --git a/clang/test/Driver/cl-zc.cpp b/clang/test/Driver/cl-zc.cpp
index c7cf5b1b6525bea..16df6799d5efaa0 100644
--- a/clang/test/Driver/cl-zc.cpp
+++ b/clang/test/Driver/cl-zc.cpp
@@ -123,6 +123,15 @@
// CHECK-CHAR8_T_: "-fno-char8_t"
+// RUN: %clang_cl /TC /dev/null /E -Xclang -dM 2> /dev/null | FileCheck -match-full-lines %s --check-prefix=NOSTDC
+// RUN: %clang_cl /TC /dev/null /E -Xclang -dM /Zc:__STDC__ 2> /dev/null | FileCheck -match-full-lines %s --check-prefix=YESSTDC
+// __STDC__ should never be defined in C++ mode with fms-compatibility.
+// RUN: %clang_cl /dev/null /E -Xclang -dM 2>&1 | FileCheck %s --check-prefix=NOSTDC
+// RUN: %clang_cl /dev/null /E -Xclang -dM /Zc:__STDC__ 2>&1 | FileCheck %s --check-prefix=ZCSTDCIGNORED
+// YESSTDC: #define __STDC__ 1
+// NOSTDC-NOT: #define __STDC__ 1
+// ZCSTDCIGNORED-NOT: #define __STDC__ 1
+// ZCSTDCIGNORED: argument unused during compilation
// These never warn, but don't have an effect yet.
diff --git a/clang/test/Driver/ms-define-stdc.c b/clang/test/Driver/ms-define-stdc.c
new file mode 100644
index 000000000000000..d5e873d21a76b59
--- /dev/null
+++ b/clang/test/Driver/ms-define-stdc.c
@@ -0,0 +1,11 @@
+// Note: %s must be preceded by --, otherwise it may be interpreted as a
+// command-line option, e.g. on Mac where %s is commonly under /Users.
+//
+// Note: see also cl-zc.cpp
+
+// RUN: %clang_cl /TC /dev/null /E -Xclang -dM /Zc:__STDC__- 2>&1 | FileCheck %s --check-prefix=ZCSTDCIGNORED
+// ZCSTDCIGNORED-NOT: #define __STDC__ 1
+// ZCSTDCIGNORED: argument unused during compilation
+
+// RUN: not %clang -Xclang -fno-ms-define-stdc %s 2>&1 | FileCheck %s --check-prefix="NOARG"
+// NOARG: error: unknown argument: '-fno-ms-define-stdc'
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