Merge topic 'cxxmodules-custom-import-std-metadata-file'

85e536b5eb gitlab-ci: test `CMAKE_CXX_STDLIB_MODULES_JSON` in CI 42621a232b Tests/CXXModules: add a label 2f101b2c8c Tests/CXXModules: support testing with custom stdlib json locations 6c178a4ae3 Tests/RunCMake: add newlines in CXXModules options 2b85541e39 cxximportstd: support setting the `import std` metadata location Acked-by: Kitware Robot <kwrobot@kitware.com> Merge-request: !11175
2026-01-04 04:40:56 -06:00 · 2025-09-15 15:39:14 +00:00
parent 0355497103 85e536b5eb
commit 2337bfc562
12 changed files with 127 additions and 49 deletions
--- a/.gitlab-ci.yml
+++ b/.gitlab-ci.yml
@@ -478,6 +478,16 @@ t:hip6.3-radeon:
    variables:
        CMAKE_CI_JOB_NIGHTLY: "true"

+t:linux-gcc-cxx-modules-reloc-ninja:
+    extends:
+        - .gcc_cxx_modules_reloc_ninja
+        - .cmake_test_linux_release
+        - .linux_x86_64_tags
+        - .run_dependent
+        - .needs_centos7_x86_64
+    variables:
+        CMAKE_CI_JOB_NIGHTLY: "true"
+
 t:linux-gcc-cxx-modules-ninja:
    extends:
        - .gcc_cxx_modules_ninja
--- a/.gitlab/ci/configure_linux_gcc_cxx_modules_reloc_ninja.cmake
+++ b/.gitlab/ci/configure_linux_gcc_cxx_modules_reloc_ninja.cmake
@@ -0,0 +1,13 @@
+# "Misplace" the `libstdc++.modules.json` file so that
+# `CMAKE_CXX_STDLIB_MODULES_JSON` is needed to use `import std`.
+set(gcc_prefix "/opt/gcc-importstd")
+set(CMake_TEST_CXX_STDLIB_MODULES_JSON
+  "${gcc_prefix}/lib64/libstdc++.modules.json"
+  CACHE FILEPATH "")
+file(MAKE_DIRECTORY
+  "${gcc_prefix}/lib64.reloc")
+file(RENAME
+  "${gcc_prefix}/lib64/libstdc++.modules.json"
+  "${CMake_TEST_CXX_STDLIB_MODULES_JSON}")
+
+include("${CMAKE_CURRENT_LIST_DIR}/configure_external_test.cmake")
--- a/.gitlab/os-linux.yml
+++ b/.gitlab/os-linux.yml
@@ -524,6 +524,13 @@
    variables:
        CMAKE_CONFIGURATION: linux_gcc_cxx_modules_ninja

+.gcc_cxx_modules_reloc_ninja:
+    extends: .gcc_cxx_modules_x86_64
+
+    variables:
+        CMAKE_CONFIGURATION: linux_gcc_cxx_modules_reloc_ninja
+        CTEST_LABELS: "CXXModules"
+
 .gcc_cxx_modules_ninja_multi:
    extends: .gcc_cxx_modules_x86_64

--- a/Help/manual/cmake-variables.7.rst
+++ b/Help/manual/cmake-variables.7.rst
@@ -45,6 +45,7 @@ Variables that Provide Information
   /variable/CMAKE_CURRENT_LIST_FILE
   /variable/CMAKE_CURRENT_LIST_LINE
   /variable/CMAKE_CURRENT_SOURCE_DIR
+   /variable/CMAKE_CXX_STDLIB_MODULES_JSON
   /variable/CMAKE_DEBUG_TARGET_PROPERTIES
   /variable/CMAKE_DIRECTORY_LABELS
   /variable/CMAKE_DL_LIBS
--- a/Help/release/dev/cxxmodules-custom-import-std-metadata-file.rst
+++ b/Help/release/dev/cxxmodules-custom-import-std-metadata-file.rst
@@ -0,0 +1,7 @@
+cxxmodules-custom-import-std-metadata-file
+------------------------------------------
+
+* The ``import std`` support learned to use the
+  :variable:`CMAKE_CXX_STDLIB_MODULES_JSON` variable to set the path to the
+  metadata file for the standard library rather than using the compiler to
+  discover its location.
--- a/Help/variable/CMAKE_CXX_STDLIB_MODULES_JSON.rst
+++ b/Help/variable/CMAKE_CXX_STDLIB_MODULES_JSON.rst
@@ -0,0 +1,11 @@
+CMAKE_CXX_STDLIB_MODULES_JSON
+-----------------------------
+
+.. versionadded:: 4.2
+
+This variable may be used to set the path to a metadata file for CMake to
+understand how the ``import std`` target for the active CXX compiler should be
+constructed.
+
+This should only be used when the compiler does not know how to discover the
+relevant module metadata file without such assistance.
--- a/Modules/Compiler/Clang-CXX-CXXImportStd.cmake
+++ b/Modules/Compiler/Clang-CXX-CXXImportStd.cmake
@@ -10,21 +10,25 @@ function (_cmake_cxx_import_std std variable)
    return ()
  endif ()

-  execute_process(
-    COMMAND
-      "${CMAKE_CXX_COMPILER}"
-      ${CMAKE_CXX_COMPILER_ID_ARG1}
-      "-print-file-name=${_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
-    OUTPUT_STRIP_TRAILING_WHITESPACE
-    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 `${_clang_modules_json_impl}.modules.json` resource\")\n"
-      PARENT_SCOPE)
-    return ()
+  if (CMAKE_CXX_STDLIB_MODULES_JSON)
+    set(_clang_libcxx_modules_json_file "${CMAKE_CXX_STDLIB_MODULES_JSON}")
+  else ()
+    execute_process(
+      COMMAND
+        "${CMAKE_CXX_COMPILER}"
+        ${CMAKE_CXX_COMPILER_ID_ARG1}
+        "-print-file-name=${_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
+      OUTPUT_STRIP_TRAILING_WHITESPACE
+      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 `${_clang_modules_json_impl}.modules.json` resource\")\n"
+        PARENT_SCOPE)
+      return ()
+    endif ()
  endif ()

  # Without this file, we do not have modules installed.
--- a/Modules/Compiler/GNU-CXX-CXXImportStd.cmake
+++ b/Modules/Compiler/GNU-CXX-CXXImportStd.cmake
@@ -6,21 +6,25 @@ function (_cmake_cxx_import_std std variable)
    return ()
  endif ()

-  execute_process(
-    COMMAND
-      "${CMAKE_CXX_COMPILER}"
-      ${CMAKE_CXX_COMPILER_ID_ARG1}
-      -print-file-name=libstdc++.modules.json
-    OUTPUT_VARIABLE _gnu_libstdcxx_modules_json_file
-    ERROR_VARIABLE _gnu_libstdcxx_modules_json_file_err
-    RESULT_VARIABLE _gnu_libstdcxx_modules_json_file_res
-    OUTPUT_STRIP_TRAILING_WHITESPACE
-    ERROR_STRIP_TRAILING_WHITESPACE)
-  if (_gnu_libstdcxx_modules_json_file_res)
-    set("${variable}"
-      "set(CMAKE_CXX${std}_COMPILER_IMPORT_STD_NOT_FOUND_MESSAGE \"Could not find `libstdc++.modules.json` resource\")\n"
-      PARENT_SCOPE)
-    return ()
+  if (CMAKE_CXX_STDLIB_MODULES_JSON)
+    set(_gnu_libstdcxx_modules_json_file "${CMAKE_CXX_STDLIB_MODULES_JSON}")
+  else ()
+    execute_process(
+      COMMAND
+        "${CMAKE_CXX_COMPILER}"
+        ${CMAKE_CXX_COMPILER_ID_ARG1}
+        -print-file-name=libstdc++.modules.json
+      OUTPUT_VARIABLE _gnu_libstdcxx_modules_json_file
+      ERROR_VARIABLE _gnu_libstdcxx_modules_json_file_err
+      RESULT_VARIABLE _gnu_libstdcxx_modules_json_file_res
+      OUTPUT_STRIP_TRAILING_WHITESPACE
+      ERROR_STRIP_TRAILING_WHITESPACE)
+    if (_gnu_libstdcxx_modules_json_file_res)
+      set("${variable}"
+        "set(CMAKE_CXX${std}_COMPILER_IMPORT_STD_NOT_FOUND_MESSAGE \"Could not find `libstdc++.modules.json` resource\")\n"
+        PARENT_SCOPE)
+      return ()
+    endif ()
  endif ()

  # Without this file, we do not have modules installed.
--- a/Modules/Compiler/MSVC-CXX-CXXImportStd.cmake
+++ b/Modules/Compiler/MSVC-CXX-CXXImportStd.cmake
@@ -1,21 +1,25 @@
 function (_cmake_cxx_import_std std variable)
-  find_file(_msvc_modules_json_file
-    NAME modules.json
-    HINTS
-      "$ENV{VCToolsInstallDir}/modules"
-    PATHS
-      "$ENV{INCLUDE}"
-      "${CMAKE_CXX_COMPILER}/../../.."
-      "${CMAKE_CXX_COMPILER}/../.."    # msvc-wine layout
-    PATH_SUFFIXES
-      ../modules
-    NO_CACHE)
-  # Without this file, we do not have modules installed.
-  if (NOT EXISTS "${_msvc_modules_json_file}")
-    set("${variable}"
-      "set(CMAKE_CXX${std}_COMPILER_IMPORT_STD_NOT_FOUND_MESSAGE \"Could not find `modules.json` resource\")\n"
-      PARENT_SCOPE)
-    return ()
+  if (CMAKE_CXX_STDLIB_MODULES_JSON)
+    set(_msvc_modules_json_file "${CMAKE_CXX_STDLIB_MODULES_JSON}")
+  else ()
+    find_file(_msvc_modules_json_file
+      NAME modules.json
+      HINTS
+        "$ENV{VCToolsInstallDir}/modules"
+      PATHS
+        "$ENV{INCLUDE}"
+        "${CMAKE_CXX_COMPILER}/../../.."
+        "${CMAKE_CXX_COMPILER}/../.."    # msvc-wine layout
+      PATH_SUFFIXES
+        ../modules
+      NO_CACHE)
+    # Without this file, we do not have modules installed.
+    if (NOT EXISTS "${_msvc_modules_json_file}")
+      set("${variable}"
+        "set(CMAKE_CXX${std}_COMPILER_IMPORT_STD_NOT_FOUND_MESSAGE \"Could not find `modules.json` resource\")\n"
+        PARENT_SCOPE)
+      return ()
+    endif ()
  endif ()

  file(READ "${_msvc_modules_json_file}" _msvc_modules_json)
--- a/Source/cmCoreTryCompile.cxx
+++ b/Source/cmCoreTryCompile.cxx
@@ -1095,6 +1095,7 @@ cm::optional<cmTryCompileResult> cmCoreTryCompile::TryCompileCode(
    vars.emplace("CMAKE_MSVC_RUNTIME_CHECKS"_s);
    vars.emplace("CMAKE_CXX_COMPILER_CLANG_SCAN_DEPS"_s);
    vars.emplace("CMAKE_VS_USE_DEBUG_LIBRARIES"_s);
+    vars.emplace("CMAKE_CXX_STDLIB_MODULES_JSON"_s);

    if (cmValue varListStr = this->Makefile->GetDefinition(
          kCMAKE_TRY_COMPILE_PLATFORM_VARIABLES)) {
--- a/Tests/RunCMake/CMakeLists.txt
+++ b/Tests/RunCMake/CMakeLists.txt
@@ -824,7 +824,13 @@ add_RunCMake_test(DependencyGraph)
 set_property(TEST RunCMake.DependencyGraph APPEND PROPERTY LABELS "Fortran")

 # Add C++ Module tests.
-add_RunCMake_test(CXXModules -DCMake_TEST_MODULE_COMPILATION=${CMake_TEST_MODULE_COMPILATION} -DCMake_TEST_MODULE_COMPILATION_RULES=${CMake_TEST_MODULE_COMPILATION_RULES})
+add_RunCMake_test(CXXModules
+  -DCMake_TEST_MODULE_COMPILATION=${CMake_TEST_MODULE_COMPILATION}
+  -DCMake_TEST_MODULE_COMPILATION_RULES=${CMake_TEST_MODULE_COMPILATION_RULES}
+  -DCMake_TEST_CXX_STDLIB_MODULES_JSON=${CMake_TEST_CXX_STDLIB_MODULES_JSON}
+)
+set_property(TEST RunCMake.CXXModules APPEND
+  PROPERTY LABELS "CXXModules")

 # ctresalloc links against CMakeLib and CTestLib, which means it can't be built
 # if CMake_TEST_EXTERNAL_CMAKE is activated (the compiler might be different.)
--- a/Tests/RunCMake/CXXModules/RunCMakeTest.cmake
+++ b/Tests/RunCMake/CXXModules/RunCMakeTest.cmake
@@ -1,6 +1,12 @@
 include(RunCMake)

-run_cmake(Inspect)
+set(stdlib_custom_json)
+if (CMake_TEST_CXX_STDLIB_MODULES_JSON)
+  list(APPEND stdlib_custom_json
+    -DCMAKE_CXX_STDLIB_MODULES_JSON=${CMake_TEST_CXX_STDLIB_MODULES_JSON})
+endif ()
+
+run_cmake(Inspect ${stdlib_custom_json})
 include("${RunCMake_BINARY_DIR}/Inspect-build/info.cmake")

 # Test negative cases where C++20 modules do not work.
@@ -149,6 +155,10 @@ function (run_cxx_module_test directory)
  else ()
    set(RunCMake_TEST_OPTIONS -DCMAKE_BUILD_TYPE=Debug)
  endif ()
+  if (directory MATCHES "import-std")
+    list(APPEND RunCMake_TEST_OPTIONS
+      ${stdlib_custom_json})
+  endif ()

  if (RunCMake_CXXModules_INSTALL)
    set(prefix "${RunCMake_BINARY_DIR}/examples/${test_name}-install")