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Experimental: add an experimental feature gate for import std

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This commit is contained in:
Ben Boeckel
2024-04-10 09:12:24 -04:00
parent f80c60df02
commit 15bbd1d9b8
27 changed files with 179 additions and 0 deletions
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21
Help/dev/experimental.rst
View File

@@ -38,3 +38,24 @@ When activated, this experimental feature provides the following:
* The package name associated with specific targets may be specified
using the ``CMAKE_EXPORT_FIND_PACKAGE_NAME`` variable and/or
``EXPORT_FIND_PACKAGE_NAME`` target property.
C++ ``import std`` support
==========================
In order to activate support for ``import std`` in C++23 and newer targets,
set
* variable ``CMAKE_EXPERIMENTAL_CXX_IMPORT_STD`` to
* value ``0e5b6991-d74f-4b3d-a41c-cf096e0b2508``.
This UUID may change in future versions of CMake. Be sure to use the value
documented here by the source tree of the version of CMake with which you are
experimenting.
When activated, this experimental feature provides the following:
* The :prop_tgt:`CXX_MODULE_STD` target property and its initializing variable
:variable:`CMAKE_CXX_MODULE_STD`.
* Targets with the property set to a true value and at least ``cxx_std_23``
may use ``import std;`` in any scanned C++ source file.

6
Help/manual/cmake-cxxmodules.7.rst
View File

@@ -92,6 +92,12 @@ Compilers which CMake natively supports module dependency scanning include:
Support for ``import std`` is limited to the following toolchain and standard
library combinations:
.. note ::
This support is provided only when experimental support for
``import std;`` has been enabled by the
``CMAKE_EXPERIMENTAL_CXX_IMPORT_STD`` gate.
Generator Support
=================

5
Help/prop_tgt/CXX_MODULE_STD.rst
View File

@@ -6,6 +6,11 @@ CXX_MODULE_STD
``CXX_MODULE_STD`` is a boolean specifying whether the target may use
``import std;`` its C++ sources or not.
.. note ::
This setting is meaningful only when experimental support for ``import
std;`` has been enabled by the ``CMAKE_EXPERIMENTAL_CXX_IMPORT_STD`` gate.
When this property is explicitly set to ``ON``, CMake will add a dependency to
a target which provides the C++ standard library's modules for the C++
standard applied to the target. This target is only applicable within the

5
Help/variable/CMAKE_CXX_MODULE_STD.rst
View File

@@ -6,5 +6,10 @@ CMAKE_CXX_MODULE_STD
Whether to add utility targets as dependencies to targets with at least
``cxx_std_23`` or not.
.. note ::
This setting is meaningful only when experimental support for ``import
std;`` has been enabled by the ``CMAKE_EXPERIMENTAL_CXX_IMPORT_STD`` gate.
This variable is used to initialize the :prop_tgt:`CXX_MODULE_STD` property on
all targets. See that target property for additional information.

11
Modules/Compiler/CMakeCommonCompilerMacros.cmake
View File

@@ -229,6 +229,17 @@ function(cmake_create_cxx_import_std std variable)
if (NOT COMMAND _cmake_cxx_import_std)
return ()
endif ()
# Check the experimental flag. Check it here to avoid triggering warnings in
# situations that don't support the feature anyways.
set(_cmake_supported_import_std_experimental "")
cmake_language(GET_EXPERIMENTAL_FEATURE_ENABLED
"CxxImportStd"
_cmake_supported_import_std_experimental)
if (NOT _cmake_supported_import_std_experimental)
return ()
endif ()
_cmake_cxx_import_std("${std}" target_definition)
string(CONCAT guarded_target_definition
"if (NOT TARGET \"__CMAKE::CXX${std}\")\n"

9
Source/cmExperimental.cxx
View File

@@ -37,6 +37,15 @@ cmExperimental::FeatureData LookupTable[] = {
{},
cmExperimental::TryCompileCondition::Always,
false },
// CxxImportStd
{ "CxxImportStd",
"0e5b6991-d74f-4b3d-a41c-cf096e0b2508",
"CMAKE_EXPERIMENTAL_CXX_IMPORT_STD",
"CMake's support for `import std;` in C++23 and newer is experimental. It "
"is meant only for experimentation and feedback to CMake developers.",
{},
cmExperimental::TryCompileCondition::Always,
false },
};
static_assert(sizeof(LookupTable) / sizeof(LookupTable[0]) ==
static_cast<size_t>(cmExperimental::Feature::Sentinel),

1
Source/cmExperimental.h
View File

@@ -19,6 +19,7 @@ public:
{
ExportPackageDependencies,
WindowsKernelModeDriver,
CxxImportStd,
Sentinel,
};

9
Source/cmGeneratorTarget.cxx
View File

@@ -32,6 +32,7 @@
#include "cmCustomCommandGenerator.h"
#include "cmCxxModuleUsageEffects.h"
#include "cmEvaluatedTargetProperty.h"
#include "cmExperimental.h"
#include "cmFileSet.h"
#include "cmFileTimes.h"
#include "cmGeneratedFileStream.h"
@@ -8502,6 +8503,14 @@ bool cmGeneratorTarget::ApplyCXXStdTargets()
break;
}
// Check the experimental feature here as well. A toolchain may have
// provided the target and skipped the check in the toolchain preparation
// logic.
if (!cmExperimental::HasSupportEnabled(
*this->Makefile, cmExperimental::Feature::CxxImportStd)) {
break;
}
this->Target->AppendProperty(
"LINK_LIBRARIES",
cmStrCat("$<BUILD_LOCAL_INTERFACE:$<$<CONFIG:", config, ">:", targetName,

8
Tests/RunCMake/CXXModules/examples/import-std-export-no-std-build-stderr.txt Normal file
View File

@@ -0,0 +1,8 @@
CMake Warning \(dev\) at .*/Modules/Compiler/CMakeCommonCompilerMacros.cmake:[0-9]* \(cmake_language\):
CMake's support for `import std;` in C\+\+23 and newer is experimental. It
is meant only for experimentation and feedback to CMake developers.
Call Stack \(most recent call first\):
.*/Modules/CMakeDetermineCompilerSupport.cmake:[0-9]* \(cmake_create_cxx_import_std\)
.*/Modules/CMakeTestCXXCompiler.cmake:[0-9]* \(CMAKE_DETERMINE_COMPILER_SUPPORT\)
CMakeLists.txt:[0-9]* \(project\)
This warning is for project developers. Use -Wno-dev to suppress it.

3
Tests/RunCMake/CXXModules/examples/import-std-export-no-std-build/CMakeLists.txt
View File

@@ -1,3 +1,6 @@
set(CMAKE_EXPERIMENTAL_CXX_IMPORT_STD
"0e5b6991-d74f-4b3d-a41c-cf096e0b2508")
cmake_minimum_required(VERSION 3.29)
project(cxx_modules_import_std_export_no_std CXX)

8
Tests/RunCMake/CXXModules/examples/import-std-export-no-std-install-stderr.txt Normal file
View File

@@ -0,0 +1,8 @@
CMake Warning \(dev\) at .*/Modules/Compiler/CMakeCommonCompilerMacros.cmake:[0-9]* \(cmake_language\):
CMake's support for `import std;` in C\+\+23 and newer is experimental. It
is meant only for experimentation and feedback to CMake developers.
Call Stack \(most recent call first\):
.*/Modules/CMakeDetermineCompilerSupport.cmake:[0-9]* \(cmake_create_cxx_import_std\)
.*/Modules/CMakeTestCXXCompiler.cmake:[0-9]* \(CMAKE_DETERMINE_COMPILER_SUPPORT\)
CMakeLists.txt:[0-9]* \(project\)
This warning is for project developers. Use -Wno-dev to suppress it.

3
Tests/RunCMake/CXXModules/examples/import-std-export-no-std-install/CMakeLists.txt
View File

@@ -1,3 +1,6 @@
set(CMAKE_EXPERIMENTAL_CXX_IMPORT_STD
"0e5b6991-d74f-4b3d-a41c-cf096e0b2508")
cmake_minimum_required(VERSION 3.29)
project(cxx_modules_import_std_export_no_std CXX)

8
Tests/RunCMake/CXXModules/examples/import-std-no-std-property-stderr.txt Normal file
View File

@@ -0,0 +1,8 @@
CMake Warning \(dev\) at .*/Modules/Compiler/CMakeCommonCompilerMacros.cmake:[0-9]* \(cmake_language\):
CMake's support for `import std;` in C\+\+23 and newer is experimental. It
is meant only for experimentation and feedback to CMake developers.
Call Stack \(most recent call first\):
.*/Modules/CMakeDetermineCompilerSupport.cmake:[0-9]* \(cmake_create_cxx_import_std\)
.*/Modules/CMakeTestCXXCompiler.cmake:[0-9]* \(CMAKE_DETERMINE_COMPILER_SUPPORT\)
CMakeLists.txt:[0-9]* \(project\)
This warning is for project developers. Use -Wno-dev to suppress it.

3
Tests/RunCMake/CXXModules/examples/import-std-no-std-property/CMakeLists.txt
View File

@@ -1,3 +1,6 @@
set(CMAKE_EXPERIMENTAL_CXX_IMPORT_STD
"0e5b6991-d74f-4b3d-a41c-cf096e0b2508")
cmake_minimum_required(VERSION 3.29)
project(cxx_modules_import_std_no_std_property CXX)

8
Tests/RunCMake/CXXModules/examples/import-std-not-in-export-build-stderr.txt Normal file
View File

@@ -0,0 +1,8 @@
CMake Warning \(dev\) at .*/Modules/Compiler/CMakeCommonCompilerMacros.cmake:[0-9]* \(cmake_language\):
CMake's support for `import std;` in C\+\+23 and newer is experimental. It
is meant only for experimentation and feedback to CMake developers.
Call Stack \(most recent call first\):
.*/Modules/CMakeDetermineCompilerSupport.cmake:[0-9]* \(cmake_create_cxx_import_std\)
.*/Modules/CMakeTestCXXCompiler.cmake:[0-9]* \(CMAKE_DETERMINE_COMPILER_SUPPORT\)
CMakeLists.txt:[0-9]* \(project\)
This warning is for project developers. Use -Wno-dev to suppress it.

3
Tests/RunCMake/CXXModules/examples/import-std-not-in-export-build/CMakeLists.txt
View File

@@ -1,3 +1,6 @@
set(CMAKE_EXPERIMENTAL_CXX_IMPORT_STD
"0e5b6991-d74f-4b3d-a41c-cf096e0b2508")
cmake_minimum_required(VERSION 3.29)
project(cxx_modules_import_std_not_in_export CXX)

8
Tests/RunCMake/CXXModules/examples/import-std-not-in-export-install-stderr.txt Normal file
View File

@@ -0,0 +1,8 @@
CMake Warning \(dev\) at .*/Modules/Compiler/CMakeCommonCompilerMacros.cmake:[0-9]* \(cmake_language\):
CMake's support for `import std;` in C\+\+23 and newer is experimental. It
is meant only for experimentation and feedback to CMake developers.
Call Stack \(most recent call first\):
.*/Modules/CMakeDetermineCompilerSupport.cmake:[0-9]* \(cmake_create_cxx_import_std\)
.*/Modules/CMakeTestCXXCompiler.cmake:[0-9]* \(CMAKE_DETERMINE_COMPILER_SUPPORT\)
CMakeLists.txt:[0-9]* \(project\)
This warning is for project developers. Use -Wno-dev to suppress it.

3
Tests/RunCMake/CXXModules/examples/import-std-not-in-export-install/CMakeLists.txt
View File

@@ -1,3 +1,6 @@
set(CMAKE_EXPERIMENTAL_CXX_IMPORT_STD
"0e5b6991-d74f-4b3d-a41c-cf096e0b2508")
cmake_minimum_required(VERSION 3.29)
project(cxx_modules_import_std_not_in_export CXX)

8
Tests/RunCMake/CXXModules/examples/import-std-stderr.txt Normal file
View File

@@ -0,0 +1,8 @@
CMake Warning \(dev\) at .*/Modules/Compiler/CMakeCommonCompilerMacros.cmake:[0-9]* \(cmake_language\):
CMake's support for `import std;` in C\+\+23 and newer is experimental. It
is meant only for experimentation and feedback to CMake developers.
Call Stack \(most recent call first\):
.*/Modules/CMakeDetermineCompilerSupport.cmake:[0-9]* \(cmake_create_cxx_import_std\)
.*/Modules/CMakeTestCXXCompiler.cmake:[0-9]* \(CMAKE_DETERMINE_COMPILER_SUPPORT\)
CMakeLists.txt:[0-9]* \(project\)
This warning is for project developers. Use -Wno-dev to suppress it.

8
Tests/RunCMake/CXXModules/examples/import-std-transitive-not-in-export-build-stderr.txt Normal file
View File

@@ -0,0 +1,8 @@
CMake Warning \(dev\) at .*/Modules/Compiler/CMakeCommonCompilerMacros.cmake:[0-9]* \(cmake_language\):
CMake's support for `import std;` in C\+\+23 and newer is experimental. It
is meant only for experimentation and feedback to CMake developers.
Call Stack \(most recent call first\):
.*/Modules/CMakeDetermineCompilerSupport.cmake:[0-9]* \(cmake_create_cxx_import_std\)
.*/Modules/CMakeTestCXXCompiler.cmake:[0-9]* \(CMAKE_DETERMINE_COMPILER_SUPPORT\)
CMakeLists.txt:[0-9]* \(project\)
This warning is for project developers. Use -Wno-dev to suppress it.

8
Tests/RunCMake/CXXModules/examples/import-std-transitive-not-in-export-install-stderr.txt Normal file
View File

@@ -0,0 +1,8 @@
CMake Warning \(dev\) at .*/Modules/Compiler/CMakeCommonCompilerMacros.cmake:[0-9]* \(cmake_language\):
CMake's support for `import std;` in C\+\+23 and newer is experimental. It
is meant only for experimentation and feedback to CMake developers.
Call Stack \(most recent call first\):
.*/Modules/CMakeDetermineCompilerSupport.cmake:[0-9]* \(cmake_create_cxx_import_std\)
.*/Modules/CMakeTestCXXCompiler.cmake:[0-9]* \(CMAKE_DETERMINE_COMPILER_SUPPORT\)
CMakeLists.txt:[0-9]* \(project\)
This warning is for project developers. Use -Wno-dev to suppress it.

3
Tests/RunCMake/CXXModules/examples/import-std-transitive/CMakeLists.txt
View File

@@ -1,3 +1,6 @@
set(CMAKE_EXPERIMENTAL_CXX_IMPORT_STD
"0e5b6991-d74f-4b3d-a41c-cf096e0b2508")
cmake_minimum_required(VERSION 3.29)
if (EXPORT_NO_STD)

3
Tests/RunCMake/CXXModules/examples/import-std/CMakeLists.txt
View File

@@ -1,3 +1,6 @@
set(CMAKE_EXPERIMENTAL_CXX_IMPORT_STD
"0e5b6991-d74f-4b3d-a41c-cf096e0b2508")
cmake_minimum_required(VERSION 3.29)
project(cxx_modules_import_std CXX)

6
Tests/RunCMake/cmake_language/Experimental/CxxImportStd-set-stderr.txt Normal file
View File

@@ -0,0 +1,6 @@
CMake Warning \(dev\) at Experimental/CxxImportStd-set.cmake:4 \(cmake_language\):
CMake's support for `import std;` in C\+\+23 and newer is experimental. It
is meant only for experimentation and feedback to CMake developers.
Call Stack \(most recent call first\):
CMakeLists.txt:3 \(include\)
This warning is for project developers. Use -Wno-dev to suppress it.

11
Tests/RunCMake/cmake_language/Experimental/CxxImportStd-set.cmake Normal file
View File

@@ -0,0 +1,11 @@
set(CMAKE_EXPERIMENTAL_CXX_IMPORT_STD
"0e5b6991-d74f-4b3d-a41c-cf096e0b2508")
cmake_language(GET_EXPERIMENTAL_FEATURE_ENABLED
"CxxImportStd"
feature_present)
if (NOT feature_present STREQUAL "TRUE")
message(FATAL_ERROR
"Expected the `CxxImportStd` feature to be enabled.")
endif ()

8
Tests/RunCMake/cmake_language/Experimental/CxxImportStd-unset.cmake Normal file
View File

@@ -0,0 +1,8 @@
cmake_language(GET_EXPERIMENTAL_FEATURE_ENABLED
"CxxImportStd"
feature_present)
if (NOT feature_present STREQUAL "FALSE")
message(FATAL_ERROR
"Expected the `CxxImportStd` feature to be disabled.")
endif ()

2
Tests/RunCMake/cmake_language/RunCMakeTest.cmake
View File

@@ -157,6 +157,8 @@ run_cmake_command(
-P ${RunCMake_SOURCE_DIR}/get_message_log_level.cmake
)
run_cmake(Experimental/CxxImportStd-set)
run_cmake(Experimental/CxxImportStd-unset)
run_cmake(Experimental/ExportPackageDependencies-set)
run_cmake(Experimental/ExportPackageDependencies-unset)
run_cmake(Experimental/WindowsKernelModeDriver-set)