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Clang/CXXImportStd: support -stdlib=libstdc++

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Fedora 42 ships `clang` with `libstdc++` as the default. Detect and
support `import std;` in this configuration.
This commit is contained in:
Ben Boeckel
2025-04-30 13:47:27 +02:00
parent 5d87f4f47c
commit 28333c4516
2 changed files with 32 additions and 19 deletions
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2
Help/manual/cmake-cxxmodules.7.rst
View File

@@ -92,7 +92,7 @@ Compilers which CMake natively supports module dependency scanning include:
Support for ``import std`` is limited to the following toolchain and standard
library combinations:
* Clang 18.1.2 and newer with ``-stdlib=libc++``
* Clang 18.1.2 and newer with ``-stdlib=libc++`` or ``-stdlib=libstdc++``
* MSVC toolset 14.36 and newer (provided with Visual Studio 17.6 Preview 2 and
newer)

49
Modules/Compiler/Clang-CXX-CXXImportStd.cmake
View File

@@ -1,7 +1,11 @@
function (_cmake_cxx_import_std std variable)
if (NOT CMAKE_CXX_STANDARD_LIBRARY STREQUAL "libc++")
if (CMAKE_CXX_STANDARD_LIBRARY STREQUAL "libc++")
set(_clang_modules_json_impl "libc++")
elseif (CMAKE_CXX_STANDARD_LIBRARY STREQUAL "libstdc++")
set(_clang_modules_json_impl "libstdc++")
else ()
set("${variable}"
"set(CMAKE_CXX${std}_COMPILER_IMPORT_STD_NOT_FOUND_MESSAGE \"Only `libc++` is supported\")\n"
"set(CMAKE_CXX${std}_COMPILER_IMPORT_STD_NOT_FOUND_MESSAGE \"Only `libc++` and `libstdc++` are supported\")\n"
PARENT_SCOPE)
return ()
endif ()
@@ -10,7 +14,7 @@ function (_cmake_cxx_import_std std variable)
COMMAND
"${CMAKE_CXX_COMPILER}"
${CMAKE_CXX_COMPILER_ID_ARG1}
-print-file-name=libc++.modules.json
"-print-file-name=${_clang_modules_json_impl}.modules.json"
OUTPUT_VARIABLE _clang_libcxx_modules_json_file
ERROR_VARIABLE _clang_libcxx_modules_json_file_err
RESULT_VARIABLE _clang_libcxx_modules_json_file_res
@@ -18,7 +22,7 @@ function (_cmake_cxx_import_std std variable)
ERROR_STRIP_TRAILING_WHITESPACE)
if (_clang_libcxx_modules_json_file_res)
set("${variable}"
"set(CMAKE_CXX${std}_COMPILER_IMPORT_STD_NOT_FOUND_MESSAGE \"Could not find `libc++.modules.json` resource\")\n"
"set(CMAKE_CXX${std}_COMPILER_IMPORT_STD_NOT_FOUND_MESSAGE \"Could not find `${_clang_modules_json_impl}.modules.json` resource\")\n"
PARENT_SCOPE)
return ()
endif ()
@@ -26,17 +30,18 @@ function (_cmake_cxx_import_std std variable)
# Without this file, we do not have modules installed.
if (NOT EXISTS "${_clang_libcxx_modules_json_file}")
set("${variable}"
"set(CMAKE_CXX${std}_COMPILER_IMPORT_STD_NOT_FOUND_MESSAGE \"`libc++.modules.json` resource does not exist\")\n"
"set(CMAKE_CXX${std}_COMPILER_IMPORT_STD_NOT_FOUND_MESSAGE \"`${_clang_modules_json_impl}.modules.json` resource does not exist\")\n"
PARENT_SCOPE)
return ()
endif ()
if (CMAKE_CXX_COMPILER_VERSION VERSION_LESS "18.1.2")
if (CMAKE_CXX_COMPILER_VERSION VERSION_LESS "18.1.2" AND
CMAKE_CXX_STANDARD_LIBRARY STREQUAL "libc++")
# The original PR had a key spelling mismatch internally. Do not support it
# and instead require a release known to have the fix.
# https://github.com/llvm/llvm-project/pull/83036
set("${variable}"
"set(CMAKE_CXX${std}_COMPILER_IMPORT_STD_NOT_FOUND_MESSAGE \"LLVM 18.1.2 is required for `libc++.modules.json` format fix\")\n"
"set(CMAKE_CXX${std}_COMPILER_IMPORT_STD_NOT_FOUND_MESSAGE \"LLVM 18.1.2 is required for `${_clang_modules_json_impl}.modules.json` format fix\")\n"
PARENT_SCOPE)
return ()
endif ()
@@ -91,9 +96,15 @@ function (_cmake_cxx_import_std std variable)
string(JSON _clang_modules_json_module_source GET "${_clang_modules_json_module}" "source-path")
string(JSON _clang_modules_json_module_is_stdlib GET "${_clang_modules_json_module}" "is-std-library")
string(JSON _clang_modules_json_module_local_arguments GET "${_clang_modules_json_module}" "local-arguments")
string(JSON _clang_modules_json_module_nsystem_include_directories LENGTH "${_clang_modules_json_module_local_arguments}" "system-include-directories")
string(JSON _clang_modules_json_module_local_arguments ERROR_VARIABLE _clang_modules_json_module_local_arguments_error GET "${_clang_modules_json_module}" "local-arguments")
string(JSON _clang_modules_json_module_nsystem_include_directories ERROR_VARIABLE _clang_modules_json_module_nsystem_include_directories_error LENGTH "${_clang_modules_json_module_local_arguments}" "system-include-directories")
if (_clang_modules_json_module_local_arguments_error)
set(_clang_modules_json_module_local_arguments "")
endif ()
if (_clang_modules_json_module_nsystem_include_directories_error)
set(_clang_modules_json_module_nsystem_include_directories 0)
endif ()
if (NOT IS_ABSOLUTE "${_clang_modules_json_module_source}")
string(PREPEND _clang_modules_json_module_source "${_clang_modules_dir}/")
endif ()
@@ -104,16 +115,18 @@ function (_cmake_cxx_import_std std variable)
set(_clang_modules_is_stdlib 1)
endif ()
math(EXPR _clang_modules_json_module_nsystem_include_directories_range "${_clang_modules_json_module_nsystem_include_directories} - 1")
foreach (_clang_modules_json_modules_system_include_directories_idx RANGE 0 "${_clang_modules_json_module_nsystem_include_directories_range}")
string(JSON _clang_modules_json_module_system_include_directory GET "${_clang_modules_json_module_local_arguments}" "system-include-directories" "${_clang_modules_json_modules_system_include_directories_idx}")
if (_clang_modules_json_module_nsystem_include_directories)
math(EXPR _clang_modules_json_module_nsystem_include_directories_range "${_clang_modules_json_module_nsystem_include_directories} - 1")
foreach (_clang_modules_json_modules_system_include_directories_idx RANGE 0 "${_clang_modules_json_module_nsystem_include_directories_range}")
string(JSON _clang_modules_json_module_system_include_directory GET "${_clang_modules_json_module_local_arguments}" "system-include-directories" "${_clang_modules_json_modules_system_include_directories_idx}")
if (NOT IS_ABSOLUTE "${_clang_modules_json_module_system_include_directory}")
string(PREPEND _clang_modules_json_module_system_include_directory "${_clang_modules_dir}/")
endif ()
list(APPEND _clang_modules_include_dirs_list
"${_clang_modules_json_module_system_include_directory}")
endforeach ()
if (NOT IS_ABSOLUTE "${_clang_modules_json_module_system_include_directory}")
string(PREPEND _clang_modules_json_module_system_include_directory "${_clang_modules_dir}/")
endif ()
list(APPEND _clang_modules_include_dirs_list
"${_clang_modules_json_module_system_include_directory}")
endforeach ()
endif ()
endforeach ()
# Split the paths into basedirs and module paths.