Skip to content

[clang-cl]: Add /std:c++23preview and update _MSVC_LANG for C++23 #112378

New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Merged
merged 3 commits into from
Oct 16, 2024
Merged

[clang-cl]: Add /std:c++23preview and update _MSVC_LANG for C++23 #112378

Show file tree
Hide file tree
Changes from all commits
Commits
Show all changes
3 commits
Select commit Hold shift + click to select a range
f44ba22
[clang-cl]: Add /std:c++23preview and update _MSVC_LANG for C++23
zmodem Oct 15, 2024
ec1149f
set _MSVC_LANG for c++26
zmodem Oct 15, 2024
a0a5175
release note
zmodem Oct 16, 2024
File filter

Filter by extension

Filter by extension
Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
2 changes: 2 additions & 0 deletions clang/docs/ReleaseNotes.rst
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -605,6 +605,8 @@ Android Support
Windows Support
^^^^^^^^^^^^^^^

- clang-cl now supports ``/std:c++23preview`` which enables C++23 features.

- Clang no longer allows references inside a union when emulating MSVC 1900+ even if `fms-extensions` is enabled.
Starting with VS2015, MSVC 1900, this Microsoft extension is no longer allowed and always results in an error.
Clang now follows the MSVC behavior in this scenario.
Expand Down
2 changes: 1 addition & 1 deletion clang/include/clang/Driver/Options.td
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -8526,7 +8526,7 @@ def _SLASH_execution_charset : CLCompileJoined<"execution-charset:">,
HelpText<"Set runtime encoding, supports only UTF-8">,
Alias<fexec_charset_EQ>;
def _SLASH_std : CLCompileJoined<"std:">,
HelpText<"Set language version (c++14,c++17,c++20,c++latest,c11,c17)">;
HelpText<"Set language version (c++14,c++17,c++20,c++23preview,c++latest,c11,c17)">;
def _SLASH_U : CLJoinedOrSeparate<"U">, HelpText<"Undefine macro">,
MetaVarName<"<macro>">, Alias<U>;
def _SLASH_validate_charset : CLFlag<"validate-charset">,
Expand Down
6 changes: 4 additions & 2 deletions clang/lib/Basic/Targets/OSTargets.cpp
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -214,9 +214,11 @@ static void addVisualCDefines(const LangOptions &Opts, MacroBuilder &Builder) {
Builder.defineMacro("_HAS_CHAR16_T_LANGUAGE_SUPPORT", Twine(1));

if (Opts.isCompatibleWithMSVC(LangOptions::MSVC2015)) {
if (Opts.CPlusPlus23)
if (Opts.CPlusPlus26)
// TODO update to the proper value.
Builder.defineMacro("_MSVC_LANG", "202004L");
Builder.defineMacro("_MSVC_LANG", "202400L");
else if (Opts.CPlusPlus23)
Builder.defineMacro("_MSVC_LANG", "202302L");
Copy link
Contributor

Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

STL mention setting _MSVC_LANG to 202600 in C++26, we should probably follow suite

Copy link
Collaborator Author

Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

Good point. My only concern is that Clang currently sets __cplusplus to 202400L in C++26 mode, so they wouldn't match which is weird. But maybe we could bump that to 202600 also?

Copy link
Collaborator

Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

Clang and GCC both use 202400L: https://godbolt.org/z/7er4doE6h -- maybe Microsoft wants to consider using the same value?

Copy link
Member

@CaseyCarter CaseyCarter Oct 15, 2024 •
edited
Loading

Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

202400L seems perfectly reasonable. I'll throw it over the fence.

EDIT: Poked our internal email chain to get approval (or at least lack of disapproval) from stakeholders and added a comment to Stephan's PR linking back here.

Copy link
Member

Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

From a user perspective, having compilers align on a particular value in the range "greater than C++23's value, but less than C++26's final value" doesn't seem important. But from Clang's perspective, I can see how it would be simpler to avoid having to vary depending on whether you're imitating MSVC or not. I'll make this change for our implementation.

Copy link
Collaborator Author

Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

I've updated the PR to set _MSVC_LANG to 202400L for C++26.

else if (Opts.CPlusPlus20)
Builder.defineMacro("_MSVC_LANG", "202002L");
else if (Opts.CPlusPlus17)
Expand Down
1 change: 1 addition & 0 deletions clang/lib/Driver/ToolChains/Clang.cpp
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -7217,6 +7217,7 @@ void Clang::ConstructJob(Compilation &C, const JobAction &JA,
.Case("c++17", "-std=c++17")
.Case("c++20", "-std=c++20")
// TODO add c++23 and c++26 when MSVC supports it.
.Case("c++23preview", "-std=c++23")
.Case("c++latest", "-std=c++26")
.Default("");
if (LanguageStandard.empty())
Expand Down
3 changes: 3 additions & 0 deletions clang/test/Driver/cl-options.c
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -605,6 +605,9 @@
// RUN: %clang_cl -fmsc-version=1900 -TP -std:c++20 -### -- %s 2>&1 | FileCheck -check-prefix=STDCXX20 %s
// STDCXX20: -std=c++20

// RUN: %clang_cl -fmsc-version=1900 -TP -std:c++23preview -### -- %s 2>&1 | FileCheck -check-prefix=STDCXX23PREVIEW %s
// STDCXX23PREVIEW: -std=c++23

// RUN: %clang_cl -fmsc-version=1900 -TP -std:c++latest -### -- %s 2>&1 | FileCheck -check-prefix=STDCXXLATEST %s
// STDCXXLATEST: -std=c++26

Expand Down
7 changes: 6 additions & 1 deletion clang/test/Preprocessor/predefined-win-macros.c
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -56,7 +56,12 @@
// RUN: %clang_cc1 %s -x c++ -E -dM -triple i686-pc-win32 -fms-extensions -fms-compatibility \
// RUN: -fms-compatibility-version=19.00 -std=c++23 -o - | FileCheck -match-full-lines %s --check-prefix=CHECK-MS-CPP2B
// CHECK-MS-CPP2B: #define _MSC_VER 1900
// CHECK-MS-CPP2B: #define _MSVC_LANG 202004L
// CHECK-MS-CPP2B: #define _MSVC_LANG 202302L

// RUN: %clang_cc1 %s -x c++ -E -dM -triple i686-pc-win32 -fms-extensions -fms-compatibility \
// RUN: -fms-compatibility-version=19.00 -std=c++26 -o - | FileCheck -match-full-lines %s --check-prefix=CHECK-MS-CPP2C
// CHECK-MS-CPP2C: #define _MSC_VER 1900
// CHECK-MS-CPP2C: #define _MSVC_LANG 202400L

// RUN: %clang_cc1 -triple i386-windows %s -E -dM -o - \
// RUN: | FileCheck -match-full-lines %s --check-prefix=CHECK-X86-WIN
Expand Down
Loading