[libc++][C++20 modules] Tests no experimental library build.

[Mordante]

Rebased to test CI.

[h-vetinari]

Depends on D158662

I think you probably meant https://reviews.llvm.org/D158661, not https://reviews.llvm.org/D158662

[ldionne]

LGTM but make sure your commit message references the right patch!

[Mordante]

In D158936#4639045, @h-vetinari wrote:

Depends on D158662

I think you probably meant https://reviews.llvm.org/D158661, not https://reviews.llvm.org/D158662

Thanks that indeed is a typo.

In D158936#4639729, @ldionne wrote:

LGTM but make sure your commit message references the right patch!

I just removed the dependency; all dependencies have landed. I tested the patch yesterday in Buildkite since to original failed. I expected it was due to the large stack, but it probably was due to the wrong dependency.

libcxx/cmake/caches/Generic-no-experimental.cmake

+set(LIBCXX_ENABLE_STD_MODULES ON CACHE BOOL "") # TODO MODULES Remove when enabled automatically.
 set(LIBCXX_TEST_PARAMS "enable_experimental=False" CACHE STRING "")
 set(LIBCXXABI_TEST_PARAMS "${LIBCXX_TEST_PARAMS}" CACHE STRING "")

libcxx/docs/Modules.rst

  * Requires CMake 3.27 for C++26 support
  * Requires Ninja 1.11
  * Requires a recent Clang 17
  * The path to the compiler may not be a symlink, ``clang-scan-deps`` does
    not handle that case properly
  * Only C++23 and C++26 are tested
  * Libc++ is not tested with modules instead of headers
  * The module ``.cppm`` files are not installed
- * The experimental ``PSTL`` library is not supported
  * Clang supports modules using GNU extensions, but libc++ does not work using
    GNU extensions.
  * Clang:
     * Including headers after importing the ``std`` module may fail. This is
       hard to solve and there is a work-around by first including all headers
       `bug report <https://github.com/llvm/llvm-project/issues/61465>`__.
 
 Blockers

libcxx/modules/CMakeLists.txt.in

 endmacro()
 
 add_library(std)
 target_sources(std
   PUBLIC FILE_SET cxx_modules TYPE CXX_MODULES FILES
     std.cppm
 )
 
-target_compile_definitions(std PRIVATE _LIBCPP_ENABLE_EXPERIMENTAL)
 target_include_directories(std SYSTEM PRIVATE @LIBCXX_CONFIGURED_INCLUDE_DIRS@)
 
 if (NOT @LIBCXX_ENABLE_EXCEPTIONS@)
   target_compile_options(std PUBLIC -fno-exceptions)
 endif()
 
 target_compile_options(std
   PUBLIC

libcxx/modules/std/execution.inc

 // -*- C++ -*-
 //===----------------------------------------------------------------------===//
 //
 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
 // See https://llvm.org/LICENSE.txt for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
 //===----------------------------------------------------------------------===//
 
+#ifdef _LIBCPP_ENABLE_EXPERIMENTAL
 export namespace std {
   // [execpol.type], execution policy type trait
   using std::is_execution_policy;
   using std::is_execution_policy_v;
 } // namespace std
 
 export namespace std::execution {
   // [execpol.seq], sequenced execution policy
export namespace std::execution {
   using std::execution::unsequenced_policy;
 
   // [execpol.objects], execution policy objects
   using std::execution::par;
   using std::execution::par_unseq;
   using std::execution::seq;
   using std::execution::unseq;
 } // namespace std::execution
+#endif // _LIBCPP_ENABLE_EXPERIMENTAL

libcxx/modules/std/ranges.inc

#endif // _LIBCPP_STD_VER >= 23
 
     // [range.drop.while], drop while view
     using std::ranges::drop_while_view;
 
     namespace views {
       using std::ranges::views::drop_while;
     } // namespace views
 
+#ifdef _LIBCPP_ENABLE_EXPERIMENTAL
     using std::ranges::join_view;
 
     namespace views {
       using std::ranges::views::join;
     } // namespace views
+#endif // _LIBCPP_ENABLE_EXPERIMENTAL
 #if 0
     using std::ranges::join_with_view;
 
     namespace views {
       using std::ranges::views::join_with;
     } // namespace views
 #endif
     using std::ranges::lazy_split_view;

libcxx/modules/std/stop_token.inc

 // -*- C++ -*-
 //===----------------------------------------------------------------------===//
 //
 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
 // See https://llvm.org/LICENSE.txt for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
 //===----------------------------------------------------------------------===//
 
 export namespace std {
 #ifndef _LIBCPP_HAS_NO_THREADS
+#  ifdef _LIBCPP_ENABLE_EXPERIMENTAL
   // [stoptoken], class stop_­token
   using std::stop_token;
 
   // [stopsource], class stop_­source
   using std::stop_source;
 
   // no-shared-stop-state indicator
   using std::nostopstate;
   using std::nostopstate_t;
 
   // [stopcallback], class template stop_­callback
   using std::stop_callback;
-#endif // _LIBCPP_HAS_NO_THREADS
+#  endif // _LIBCPP_ENABLE_EXPERIMENTAL
+#endif   // _LIBCPP_HAS_NO_THREADS
 } // namespace std

libcxx/test/lit.local.cfg

):
     build = os.path.join(config.test_exec_root, "__config_module__")
     config.substitutions = appendToSubstitution(
         config.substitutions,
         "%{compile_flags}",
         "-fprebuilt-module-path="
         + os.path.join(config.test_exec_root, "__config_module__/CMakeFiles/std.dir"),
     )
 
-    flags = getSubstitution("%{flags}", config)
     cmake = getSubstitution("%{cmake}", config)
+    flags = getSubstitution("%{flags}", config)
+    if "c++experimental" in config.available_features:
+        flags = f"{flags} -D_LIBCPP_ENABLE_EXPERIMENTAL"
 
     subprocess.check_call(
         [cmake, f"-DCMAKE_CXX_STANDARD={std}", f"-DCMAKE_CXX_FLAGS={flags}", build],
         env={},
     )
     subprocess.check_call([cmake, "--build", build, "--", "-v"], env={})
     config.substitutions = appendToSubstitution(
         config.substitutions,
         "%{link_flags}",
         os.path.join(build, "libc++std.a"),
     )

libcxx/utils/ci/buildkite-pipeline.yml

- label: "No wide characters"
       timeout_in_minutes: 120
 
     - label: "No experimental features"
       command: "libcxx/utils/ci/run-buildbot generic-no-experimental"
       artifact_paths:
         - "**/test-results.xml"
         - "**/*.abilist"
       env:
-          CC: "clang-${LLVM_HEAD_VERSION}"
-          CXX: "clang++-${LLVM_HEAD_VERSION}"
+          # Note: Modules require and absolute path for clang-scan-deps
+          # https://github.com/llvm/llvm-project/issues/61006
+          CC: "/usr/lib/llvm-${LLVM_HEAD_VERSION}/bin/clang"
+          CXX: "/usr/lib/llvm-${LLVM_HEAD_VERSION}/bin/clang++"
+          CMAKE: "/opt/bin/cmake"
           ENABLE_CLANG_TIDY: "On"
       agents:
         queue: "libcxx-builders"
         os: "linux"
       retry:
         automatic:
           - exit_status: -1  # Agent was lost
             limit: 2