[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 +1,23 @@
+//===----------------------------------------------------------------------===//
+//
+// 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
+//
+//===----------------------------------------------------------------------===//
+
+// UNSUPPORTED: c++03, c++11, c++14, c++17, c++20
+// UNSUPPORTED: clang-modules-build
+// UNSUPPORTED: gcc
+
+// 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 +1,25 @@
+//===----------------------------------------------------------------------===//
+//
+// 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
+//
+//===----------------------------------------------------------------------===//
+
+// UNSUPPORTED: c++03, c++11, c++14, c++17, c++20
+// UNSUPPORTED: clang-modules-build
+// UNSUPPORTED: gcc
+
+// 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 +1,25 @@
+//===----------------------------------------------------------------------===//
+//
+// 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
+//
+//===----------------------------------------------------------------------===//
+
+// UNSUPPORTED: c++03, c++11, c++14, c++17, c++20
+// UNSUPPORTED: clang-modules-build
+// UNSUPPORTED: gcc
+
+// 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

@@ -8,11 +8,14 @@
 
 // UNSUPPORTED: c++03, c++11, c++14, c++17
 // UNSUPPORTED: clang-modules-build
+// UNSUPPORTED: gcc
 
-// 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

@@ -8,11 +8,14 @@
 
 // UNSUPPORTED: c++03, c++11, c++14, c++17, c++20
 // UNSUPPORTED: clang-modules-build
+// UNSUPPORTED: gcc
 
-// 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 +317,18 @@ 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

libcxx/utils/libcxx/test/format.py

@@ -91,6 +91,8 @@ def parseScript(test, preamble):
     # Parse the test file, including custom directives
     additionalCompileFlags = []
     fileDependencies = []
+    modules = []  # The enabled modules
+    moduleCompileFlags = []  # The compilation flags to use modules
     parsers = [
         lit.TestRunner.IntegratedTestKeywordParser(
             "FILE_DEPENDENCIES:",
@@ -102,6 +104,11 @@ def parseScript(test, preamble):
             lit.TestRunner.ParserKind.SPACE_LIST,
             initial_value=additionalCompileFlags,
         ),
+        lit.TestRunner.IntegratedTestKeywordParser(
+            "MODULES:",
+            lit.TestRunner.ParserKind.SPACE_LIST,
+            initial_value=modules,
+        ),
     ]
 
     # Add conditional parsers for ADDITIONAL_COMPILE_FLAGS. This should be replaced by first
@@ -131,13 +138,65 @@ def parseScript(test, preamble):
     script += preamble
     script += scriptInTest
 
+    has_std_module = False
+    has_std_compat_module = False
+    for module in modules:
+        if module == "std":
+            has_std_module = True
+        elif module == "std.compat":
+            has_std_compat_module = True
+        else:
+            script.insert(
+                0,
+                f"echo \"The module '{module}' is not valid, use 'std' or 'std.compat'\"",
+            )
+            script.insert(1, "false")
+            return script
+
+    if modules:
+        # This flag is needed for both modules.
+        moduleCompileFlags.append("-fprebuilt-module-path=%T")
+
+        # Building the modules needs to happen before the other script commands
+        # are executed. Therefore the commands are added to the front of the
+        # list.
+        if has_std_compat_module:
+            script.insert(
+                0,
+                "%dbg(MODULE std.compat) %{cxx} %{flags} %{compile_flags} "
+                "-Wno-reserved-module-identifier -Wno-reserved-user-defined-literal "
+                "--precompile -o %T/std.compat.pcm -c %{module}/std.compat.cppm",
+            )
+            moduleCompileFlags.append("%T/std.compat.pcm")
+
+        # Make sure the std module is added before std.compat.
+        # Libc++'s std.compat module will depend on its std module.
+        # It is not known whether the compiler expects the modules in the order
+        # of their dependencies. However it's trivial to provide them in that
+        # order.
+        if has_std_module:
+            script.insert(
+                0,
+                "%dbg(MODULE std) %{cxx} %{flags} %{compile_flags} "
+                "-Wno-reserved-module-identifier -Wno-reserved-user-defined-literal "
+                "--precompile -o %T/std.pcm -c %{module}/std.cppm",
+            )
+            moduleCompileFlags.append("%T/std.pcm")
+
     # Add compile flags specified with ADDITIONAL_COMPILE_FLAGS.
     substitutions = [
         (s, x + " " + " ".join(additionalCompileFlags))
         if s == "%{compile_flags}"
         else (s, x)
         for (s, x) in substitutions
     ]
+    # In order to use modules, additional compilation flags are required.
+    # Adding these to the %{compile_flags} gives a chicken and egg issue:
+    # - the modules need to be built with the same compilation flags as the
+    #   tests,
+    # - except for the module dependency, which does not exist.
+    # The issue is resolved by adding a private substitution.
+    substitutions.append(("%{module_flags}", " ".join(moduleCompileFlags)))
 
     # Perform substitutions in the script itself.
     script = lit.TestRunner.applySubstitutions(
@@ -191,6 +250,7 @@ class CxxStandardLibraryTest(lit.formats.FileBasedTest):
     constructs:
         %{cxx}           - A command that can be used to invoke the compiler
         %{compile_flags} - Flags to use when compiling a test case
+        %{module_flags}  - Flags to use when compiling a test case that imports modules
         %{link_flags}    - Flags to use when linking a test case
         %{flags}         - Flags to use either when compiling or linking a test case
         %{exec}          - A command to prefix the execution of executables
@@ -223,6 +283,12 @@ class CxxStandardLibraryTest(lit.formats.FileBasedTest):
             allows adding special compilation flags without having to use a
             .sh.cpp test, which would be more powerful but perhaps overkill.
 
+        // MODULE: std std.compat
+
+           This directive will build the required C++23 standard library
+           modules and add the additional compiler flags in
+           %{module_flags}. (Libc++ offers these modules in C++20 as an
+           extension.)
 
     Additional provided substitutions and features
     ==============================================
@@ -288,22 +354,22 @@ def execute(self, test, litConfig):
             ".compile.pass.mm"
         ):
             steps = [
-                "%dbg(COMPILED WITH) %{cxx} %s %{flags} %{compile_flags} -fsyntax-only"
+                "%dbg(COMPILED WITH) %{cxx} %s %{flags} %{compile_flags} %{module_flags} -fsyntax-only"
             ]
             return self._executeShTest(test, litConfig, steps)
         elif filename.endswith(".compile.fail.cpp"):
             steps = [
-                "%dbg(COMPILED WITH) ! %{cxx} %s %{flags} %{compile_flags} -fsyntax-only"
+                "%dbg(COMPILED WITH) ! %{cxx} %s %{flags} %{compile_flags} %{module_flags} -fsyntax-only"
             ]
             return self._executeShTest(test, litConfig, steps)
         elif filename.endswith(".link.pass.cpp") or filename.endswith(".link.pass.mm"):
             steps = [
-                "%dbg(COMPILED WITH) %{cxx} %s %{flags} %{compile_flags} %{link_flags} -o %t.exe"
+                "%dbg(COMPILED WITH) %{cxx} %s %{flags} %{compile_flags} %{module_flags} %{link_flags} -o %t.exe"
             ]
             return self._executeShTest(test, litConfig, steps)
         elif filename.endswith(".link.fail.cpp"):
             steps = [
-                "%dbg(COMPILED WITH) %{cxx} %s %{flags} %{compile_flags} -c -o %t.o",
+                "%dbg(COMPILED WITH) %{cxx} %s %{flags} %{compile_flags} %{module_flags} -c -o %t.o",
                 "%dbg(LINKED WITH) ! %{cxx} %t.o %{flags} %{link_flags} -o %t.exe",
             ]
             return self._executeShTest(test, litConfig, steps)
@@ -321,7 +387,7 @@ def execute(self, test, litConfig):
         # suffixes above too.
         elif filename.endswith(".pass.cpp") or filename.endswith(".pass.mm"):
             steps = [
-                "%dbg(COMPILED WITH) %{cxx} %s %{flags} %{compile_flags} %{link_flags} -o %t.exe",
+                "%dbg(COMPILED WITH) %{cxx} %s %{flags} %{compile_flags} %{module_flags} %{link_flags} -o %t.exe",
                 "%dbg(EXECUTED AS) %{exec} %t.exe",
             ]
             return self._executeShTest(test, litConfig, steps)

libcxx/utils/libcxx/test/modules.py

@@ -113,20 +113,21 @@ class module_test_generator:
     clang_tidy_plugin: str
     compiler: str
     compiler_flags: str
+    module: str
 
     def write_lit_configuration(self):
         print(
             f"""\
 // UNSUPPORTED: c++03, c++11, c++14, c++17
 // UNSUPPORTED: clang-modules-build
 
-// XFAIL: *
-
 // REQUIRES: has-clang-tidy
 
 // The GCC compiler flags are not always compatible with clang-tidy.
 // UNSUPPORTED: gcc
 
+// MODULES: {self.module}
+
 // RUN: echo -n > {self.tmp_prefix}.all_partitions
 """
         )