add build.c++.modules policy

6 files changed, 99 insertions, 0 deletions

diff --git a/tests/projects/c++/modules/stl_headerunit_cpp_only/.gitignore b/tests/projects/c++/modules/stl_headerunit_cpp_only/.gitignore
new file mode 100644
index 000000000..152105761
--- /dev/null
+++ b/tests/projects/c++/modules/stl_headerunit_cpp_only/.gitignore
@@ -0,0 +1,8 @@
+# Xmake cache
+.xmake/
+build/
+
+# MacOS Cache
+.DS_Store
+
+
diff --git a/tests/projects/c++/modules/stl_headerunit_cpp_only/src/main.cpp b/tests/projects/c++/modules/stl_headerunit_cpp_only/src/main.cpp
new file mode 100644
index 000000000..dc71bb4c6
--- /dev/null
+++ b/tests/projects/c++/modules/stl_headerunit_cpp_only/src/main.cpp
@@ -0,0 +1,9 @@
+import <iostream>;
+
+using namespace std;
+
+int main(int argc, char** argv)
+{
+    cout << "hello world!" << endl;
+    return 0;
+}
diff --git a/tests/projects/c++/modules/stl_headerunit_cpp_only/test.lua b/tests/projects/c++/modules/stl_headerunit_cpp_only/test.lua
new file mode 100644
index 000000000..c18e5a1d0
--- /dev/null
+++ b/tests/projects/c++/modules/stl_headerunit_cpp_only/test.lua
@@ -0,0 +1 @@
+inherit(".test_headerunits")
diff --git a/tests/projects/c++/modules/stl_headerunit_cpp_only/xmake.lua b/tests/projects/c++/modules/stl_headerunit_cpp_only/xmake.lua
new file mode 100644
index 000000000..101a95fe7
--- /dev/null
+++ b/tests/projects/c++/modules/stl_headerunit_cpp_only/xmake.lua
@@ -0,0 +1,76 @@
+add_rules("mode.debug", "mode.release")
+
+target("test")
+    set_kind("binary")
+    add_files("src/*.cpp")
+    set_languages("c++20")
+    set_policy("build.c++.modules", true)
+--
+-- If you want to known more usage about xmake, please see https://xmake.io
+--
+-- ## FAQ
+--
+-- You can enter the project directory firstly before building project.
+--
+--   $ cd projectdir
+--
+-- 1. How to build project?
+--
+--   $ xmake
+--
+-- 2. How to configure project?
+--
+--   $ xmake f -p [macosx|linux|iphoneos ..] -a [x86_64|i386|arm64 ..] -m [debug|release]
+--
+-- 3. Where is the build output directory?
+--
+--   The default output directory is `./build` and you can configure the output directory.
+--
+--   $ xmake f -o outputdir
+--   $ xmake
+--
+-- 4. How to run and debug target after building project?
+--
+--   $ xmake run [targetname]
+--   $ xmake run -d [targetname]
+--
+-- 5. How to install target to the system directory or other output directory?
+--
+--   $ xmake install
+--   $ xmake install -o installdir
+--
+-- 6. Add some frequently-used compilation flags in xmake.lua
+--
+-- @code
+--    -- add debug and release modes
+--    add_rules("mode.debug", "mode.release")
+--
+--    -- add macro defination
+--    add_defines("NDEBUG", "_GNU_SOURCE=1")
+--
+--    -- set warning all as error
+--    set_warnings("all", "error")
+--
+--    -- set language: c99, c++11
+--    set_languages("c99", "c++11")
+--
+--    -- set optimization: none, faster, fastest, smallest
+--    set_optimize("fastest")
+--
+--    -- add include search directories
+--    add_includedirs("/usr/include", "/usr/local/include")
+--
+--    -- add link libraries and search directories
+--    add_links("tbox")
+--    add_linkdirs("/usr/local/lib", "/usr/lib")
+--
+--    -- add system link libraries
+--    add_syslinks("z", "pthread")
+--
+--    -- add compilation and link flags
+--    add_cxflags("-stdnolib", "-fno-strict-aliasing")
+--    add_ldflags("-L/usr/local/lib", "-lpthread", {force = true})
+--
+-- @endcode
+--
+
diff --git a/xmake/core/project/policy.lua b/xmake/core/project/policy.lua
index 27d0b9d6a..ef7851317 100644
--- a/xmake/core/project/policy.lua
+++ b/xmake/core/project/policy.lua
@@ -51,6 +51,8 @@ function policy.policies()
             ["build.warning"]                    = {description = "Enable build warning output.", type = "boolean"},
             -- enable LTO linker-time optimization for c/c++ building.
             ["build.optimization.lto"]           = {description = "Enable LTO linker-time optimization for c/c++ building.", type = "boolean"},
+            -- enable C++ modules for C++ building, even if no .mpp is involved in the compilation
+            ["build.c++.modules"]                = {description = "Enable C++ modules for C++ building.", type = "boolean"},
             -- preprocessor configuration for ccache/distcc, we can disable linemarkers to speed up preprocess
             ["preprocessor.linemarkers"]         = {description = "Enable linemarkers for preprocessor.", default = true, type = "boolean"},
             -- preprocessor configuration for ccache/distcc, we can disable it to avoid cache object file with __DATE__, __TIME__
diff --git a/xmake/rules/c++/modules/modules_support/common.lua b/xmake/rules/c++/modules/modules_support/common.lua
index aa7c0fb59..138c8e36f 100644
--- a/xmake/rules/c++/modules/modules_support/common.lua
+++ b/xmake/rules/c++/modules/modules_support/common.lua
@@ -140,6 +140,9 @@ function contains_modules(target)
     -- we can not use `"c++.build.modules.builder"`, because it contains sourcekind/cxx.
     local target_with_modules = target:sourcebatches()["c++.build.modules"] and true or false
     if not target_with_modules then
+        target_with_modules = target:policy("build.c++.modules")
+    end
+    if not target_with_modules then
         for _, dep in ipairs(target:orderdeps()) do
             local sourcebatches = dep:sourcebatches()
             if sourcebatches["c++.build.modules"] then