Add c++ modules ts build rules

[waruqi]

Roadmap

• module interface files
  • .ixx (msvc)
  • .cppm (clang)
  • .mxx/.mpp (recommand/xmake)
• clang
  • hello
  • impl_unit
  • inline_and_template
  • class
  • dependence
• gcc
• msvc (>= vs2017)
  • hello
  • impl_unit
  • inline_and_template
  • class
  • dependence

Examples

• https://github.com/xmake-io/xmake/tree/dev/tests/projects/c%2B%2B/modules

References

• https://build2.org/doc/modules-cppcon2017.pdf
• C++ modules support #386
• https://github.com/mutouyun/cncppcon2018-cppmodules
• https://clang.llvm.org/docs/Modules.html
• https://gcc.gnu.org/wiki/cxx-modules

[waruqi]

Example (hello)

projectdir
  - src
    - hello.mpp
    - main.cpp
  - xmake.lua

xmake.lua

target("hello")
    set_kind("binary")
    add_files("src/*.cpp", "src/*.mpp") 

hello.mpp

// module;
#include <cstdio>
export module hello;
using namespace std;

export namespace hello {
    void say(const char* str) {
        printf("%s\n", str);
    }
}

main.cpp

import hello;

int main() {
    hello::say("hello module!");
    return 0;
}

Build and output

ruki:hello ruki$ xmake 
[  0%]: ccache compiling.release src/hello.mpp
[ 50%]: ccache compiling.release src/main.cpp
[100%]: linking.release hello
build ok!👌

ruki:hello ruki$ xmake -r -v
[  0%]: ccache compiling.release src/hello.mpp
/usr/local/bin/ccache /usr/bin/xcrun -sdk macosx clang -c -fmodules-ts --precompile -x c++-module -Qunused-arguments -arch x86_64 -fpascal-strings -fmessage-length=0 -mmacosx-version-min=10.14 -isysroot /Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX10.14.sdk -o build/.objs/hello/macosx/x86_64/release/src/hello.mpp.o.pcm src/hello.mpp
/usr/local/bin/ccache /usr/bin/xcrun -sdk macosx clang -c -fmodules-ts -Qunused-arguments -arch x86_64 -fpascal-strings -fmessage-length=0 -mmacosx-version-min=10.14 -isysroot /Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX10.14.sdk -o build/.objs/hello/macosx/x86_64/release/src/hello.mpp.o build/.objs/hello/macosx/x86_64/release/src/hello.mpp.o.pcm
[ 50%]: ccache compiling.release src/main.cpp
/usr/local/bin/ccache /usr/bin/xcrun -sdk macosx clang -c -fmodules-ts -fmodule-file=build/.objs/hello/macosx/x86_64/release/src/hello.mpp.o.pcm -Qunused-arguments -arch x86_64 -fpascal-strings -fmessage-length=0 -mmacosx-version-min=10.14 -isysroot /Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX10.14.sdk -o build/.objs/hello/macosx/x86_64/release/src/main.cpp.o src/main.cpp
[100%]: linking.release hello
"/usr/bin/xcrun -sdk macosx clang++" -o build/macosx/x86_64/release/hello build/.objs/hello/macosx/x86_64/release/src/hello.mpp.o build/.objs/hello/macosx/x86_64/release/src/main.cpp.o -arch x86_64 -mmacosx-version-min=10.14 -isysroot /Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX10.14.sdk -stdlib=libc++ -lz
build ok!👌

[waruqi]

There is currently no environment to compile gcc toolchains with c++modules. (in svn://gcc.gnu.org/svn/gcc/branches/c++-modules)

And gcc's c++ modules implementation is not perfect, for the time being I don't support it.

目前我这没环境单独做一份支持c++modules的gcc toolchains来测试c++modules，并且目前gcc对c++modules支持也还不是很完善，等之后集成到gcc正式版的时候，我再对gcc做支持好了，目前不折腾了。。

[sunxfancy]

关于GCC相关的C++ 20的支持有计划更新吗？C++20的module的header如果要import，需要先编译，不知道有没有什么思路可以讨论一下的？

[waruqi]

gcc 不是老早支持了么。。

[sunxfancy]

GCC 在import 等system heaaders需要提前编译，例如：

g++ -std=c++20 -fmodules-ts -c -x c++-system-header iostream

但我好像没有找到相关支持的接口，这样GCC就没办法import这些header从而无法发挥其相关的编译优势。

[waruqi]

xmake 支持 gcc11 c++ modules 编译，但 std modules 目前不归 xmake 管，gcc11 没提供编译好的，暂时不支持，xmake 不会额外给你编译依赖的 std modules，这应该是 gcc 自身该提供的支持，而不是让构建工具支持。

像 msvc 都是自带编译好的 std modules 可用。

。。你可以直接用 #include <iostream>