[libc++][modules] Adds module testing.

This adds a new module test infrastructure. This requires tagging tests
using modules. The test runner uses this information to determine the
compiler flags needed to build and use the module.

Currently modules are build per test, which allows testing them for
tests with ADDITIONAL_COMPILE_FLAGS. At the moment only 4 tests use
modules. Therefore the performance penalty is not measurable. If in the
future more tests use modules it would be good to measure the overhead
and determine whether it's acceptable.

Author: mordante

libcxx/test/libcxx/module_std.gen.py

@@ -29,7 +29,8 @@
     "%{clang-tidy}",
     "%{test-tools}/clang_tidy_checks/libcxx-tidy.plugin",
     "%{cxx}",
-    "%{flags} %{compile_flags}",
+    "%{flags} %{compile_flags} %{module_flags}",
+    "std",
 )
 
 

libcxx/test/libcxx/module_std_compat.gen.py

@@ -29,7 +29,8 @@
     "%{clang-tidy}",
     "%{test-tools}/clang_tidy_checks/libcxx-tidy.plugin",
     "%{cxx}",
-    "%{flags} %{compile_flags}",
+    "%{flags} %{compile_flags} %{module_flags}",
+    "std.compat",
 )
 
 

libcxx/test/libcxx/selftest/modules/no-modules.sh.cpp

@@ -0,0 +1,12 @@
+//===----------------------------------------------------------------------===//
+//
+// 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
+//
+//===----------------------------------------------------------------------===//
+
+// Make sure that the module flags are empty when no module is supplied.
+
+// MODULES:
+// RUN: echo "%{module_flags}"  | grep "^$"

libcxx/test/libcxx/selftest/modules/std-and-std.compat-module.sh.cpp

@@ -0,0 +1,19 @@
+//===----------------------------------------------------------------------===//
+//
+// 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
+//
+//===----------------------------------------------------------------------===//
+
+// XFAIL: has-no-module-support
+
+// Make sure that the module flags contain the expected elements.
+// The tests only look for the expected components and not the exact flags.
+// Otherwise changing the location of the module breaks this test.
+
+// MODULES: std std.compat
+//
+// RUN: echo "%{module_flags}" | grep -- "-fprebuilt-module-path="
+// RUN: echo "%{module_flags}" | grep "std.pcm"
+// RUN: echo "%{module_flags}" | grep "std.compat.pcm"

libcxx/test/libcxx/selftest/modules/std-module.sh.cpp

@@ -0,0 +1,21 @@
+//===----------------------------------------------------------------------===//
+//
+// 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
+//
+//===----------------------------------------------------------------------===//
+
+// XFAIL: has-no-module-support
+
+// Make sure that the module flags contain the expected elements.
+// The tests only look for the expected components and not the exact flags.
+// Otherwise changing the location of the module breaks this test.
+
+// MODULES: std
+//
+// RUN: echo "%{module_flags}" | grep -- "-fprebuilt-module-path="
+// RUN: echo "%{module_flags}" | grep "std.pcm"
+
+// The std module should not provide the std.compat module
+// RUN: echo "%{module_flags}" | grep -v "std.compat.pcm"

libcxx/test/libcxx/selftest/modules/std.compat-module.sh.cpp

@@ -0,0 +1,21 @@
+//===----------------------------------------------------------------------===//
+//
+// 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
+//
+//===----------------------------------------------------------------------===//
+
+// XFAIL: has-no-module-support
+
+// Make sure that the module flags contain the expected elements.
+// The tests only look for the expected components and not the exact flags.
+// Otherwise changing the location of the module breaks this test.
+
+// MODULES: std.compat
+//
+// RUN: echo "%{module_flags}" | grep -- "-fprebuilt-module-path="
+// RUN: echo "%{module_flags}" | grep "std.compat.pcm"
+
+// It's unspecified whether std.compat is built on the std module.
+// Therefore don't test its presence

libcxx/test/libcxx/selftest/modules/unknown-module.compile.pass.cpp

@@ -0,0 +1,13 @@
+//===----------------------------------------------------------------------===//
+//
+// 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
+//
+//===----------------------------------------------------------------------===//
+
+// Make sure that modules that are unknown fail.
+
+// MODULES: this_module_is_not_a_standard_library_module
+
+// XFAIL: *

libcxx/test/std/modules/std.compat.pass.cpp

@@ -9,10 +9,12 @@
 // UNSUPPORTED: c++03, c++11, c++14, c++17
 // UNSUPPORTED: clang-modules-build
 
-// XFAIL: *
+// XFAIL: has-no-module-support
 
 // A minimal test to validate import works.
 
+// MODULES: std.compat
+
 import std.compat;
 
 int main(int, char**) { return !(::strlen("Hello modular world") == 19); }

libcxx/test/std/modules/std.pass.cpp

@@ -9,10 +9,12 @@
 // UNSUPPORTED: c++03, c++11, c++14, c++17, c++20
 // UNSUPPORTED: clang-modules-build
 
-// XFAIL: *
+// XFAIL: has-no-module-support
 
 // A minimal test to validate import works.
 
+// MODULES: std
+
 import std;
 
 int main(int, char**) {

libcxx/utils/libcxx/test/features.py

@@ -317,6 +317,19 @@ def _getAndroidDeviceApi(cfg):
             AddSubstitution("%{clang-tidy}", lambda cfg: _getSuitableClangTidy(cfg))
         ],
     ),
+    # Whether module support for the platform is available.
+    Feature(
+        name="has-no-module-support",
+        # The libc of these platforms have functions with internal linkages.
+        # This is not allowed per C11 7.1.2 Standard headers/6
+        #  Any declaration of a library function shall have external linkage.
+        when=lambda cfg: "__ANDROID__" in compilerMacros(cfg)
+        or "__PICOLIBC__" in compilerMacros(cfg)
+        or platform.system().lower().startswith("aix")
+        # Avoid building on platforms that don't support modules properly.
+        or not hasCompileFlag(cfg, "-Wno-reserved-module-identifier"),
+    ),
+
 ]
 
 # Deduce and add the test features that that are implied by the #defines in