[Modules] xmake uses inconsistent STL for different targets

[ChuanqiXu9]

Xmake Version

xmake v2.7.6+master.7f8eefb8a

Operating System Version and Architecture

linux

Describe Bug

I am trying to compile https://github.com/alibaba/async_simple/tree/CXX20Modules with xmake.

add_rules("mode.debug", "mode.release")

set_languages("c++20")

target("std")
    set_kind("static")
    add_files("third_party_module/stdmodules/*.cppm")
    add_includedirs("third_party_module/stdmodules")
    set_languages("c++20")

target("asio")
    set_kind("static")
    add_files("third_party_module/asio/asio.cppm")
    add_includedirs("third_party_module/asio")
    set_languages("c++20")

target("async_simple")
    set_kind("static")
    add_files("async_simple_module/*.cppm",
              "async_simple_module/coro/*.cppm",
              "async_simple_module/executors/*.cppm",
              "async_simple_module/uthread/*.cppm",
              "async_simple_module/uthread/internal/*.cppm",
              "async_simple_module/util/*.cppm")
    add_deps("std")
    set_languages("c++20")

Bug I meet a surprising error message:

error: In module 'async_simple:Common' imported from async_simple_module/util/Condition.cppm:27:
In module 'std' imported from /home/chuanqi.xcq/async_simple_module/async_simple_module/Common.cppm:17:
In module 'std:cstdint' imported from /home/chuanqi.xcq/async_simple_module/third_party_module/stdmodules/std.cppm:23:
/usr/lib/gcc/x86_64-redhat-linux/10/../../../../include/c++/10/cstddef:138:18: error: 'std::operator&' has different definitions in different modules; definition in module 'std:cstdint.<global>' first difference is 1st parameter with name '__l'
  operator&(byte __l, byte __r) noexcept
            ~~~~~^~~
/home/chuanqi.xcq/llvm-project-for-work/build/bin/../include/c++/v1/cstddef:107:34: note: but in '' found 1st parameter with name '__lhs'
constexpr byte  operator& (byte  __lhs, byte __rhs) noexcept
                           ~~~~~~^~~~~
1 error generated.

Look carefully into the error message, I found the first one uses libstdc++ while the second one uses libc++. So here is the problem. Then I find that xmake wouldn't append -stdlib=libc++ for module units of std but xmake would append -stdlib=libc++ for module units under async_simple.

Here is the command for std:utility:

/home/chuanqi.xcq/llvm-project-for-work/build/bin/clang++ -c -x c++-module -fmodule-output=build/.gens/std/linux/x86_64/release/rules/modules/cache/b8e837a8/std:utility.pcm -Qunused-arguments -m64 -fvisibility=hidden -fvisibility-inlines-hidden -O3 -std=c++20 -Ithird_party_module/stdmodules -DNDEBUG -fmodules-cache-path=build/.gens/std/linux/x86_64/release/rules/modules/cache -o build/.objs/std/linux/x86_64/release/third_party_module/stdmodules/utility.cppm.o third_party_module/stdmodules/utility.cppm

Here is the command for async_simple:Unit

/home/chuanqi.xcq/llvm-project-for-work/build/bin/clang++ -c -x c++-module -fmodule-output=build/.gens/async_simple/linux/x86_64/release/rules/modules/cache/321e8fd9/async_simple:Unit.pcm -Qunused-arguments -m64 -fvisibility=hidden -fvisibility-inlines-hidden -O3 -std=c++20 -stdlib=libc++ -DNDEBUG -fmodules-cache-path=build/.gens/async_simple/linux/x86_64/release/rules/modules/cache -o build/.objs/async_simple/linux/x86_64/release/async_simple_module/Unit.cppm.o async_simple_module/Unit.cppm

Expected Behavior

The targets in the same project should use the same configuration for STL.

Project Configuration

No response

Additional Information and Error Logs

No response

[waruqi]

I have improved it, try it again. 9e8183b

@Arthapz

And I need remove std::ignore

diff --git a/third_party_module/stdmodules/tuple.cppm b/third_party_module/stdmodules/tuple.cppm
index e4bd882..9226d0b 100644
--- a/third_party_module/stdmodules/tuple.cppm
+++ b/third_party_module/stdmodules/tuple.cppm
@@ -7,5 +7,5 @@ export namespace std {
     using std::get;
     using std::tie;
     using std::make_tuple;
-    using std::ignore;
+//    using std::ignore;
 }

And I got errors.

.o async_simple_module/uthread/Await.cppm
error: async_simple_module/uthread/Await.cppm:85:23: error: no type named 'result_of_t' in namespace 'std'
        typename std::result_of_t<decltype(fn)(C, Ts && ...)>::ValueType;
        ~~~~~~~~~~~~~~^~~~~~~~~~~
async_simple_module/uthread/Await.cppm:85:34: error: expected ';' after alias declaration
        typename std::result_of_t<decltype(fn)(C, Ts && ...)>::ValueType;
                                 ^
                                 ;
async_simple_module/uthread/Await.cppm:86:13: error: use of undeclared identifier 'ValueType'
    Promise<ValueType> p;
            ^
async_simple_module/uthread/Await.cppm:110:23: error: no type named 'result_of_t' in namespace 'std'
        typename std::result_of_t<decltype(fn)(Ts && ...)>::ValueType;
        ~~~~~~~~~~~~~~^~~~~~~~~~~
async_simple_module/uthread/Await.cppm:110:34: error: expected ';' after alias declaration
        typename std::result_of_t<decltype(fn)(Ts && ...)>::ValueType;
                                 ^
                                 ;
async_simple_module/uthread/Await.cppm:111:13: error: use of undeclared identifier 'ValueType'
    Promise<ValueType> p;
            ^
6 errors generated.

@ChuanqiXu9

[ChuanqiXu9]

Thanks. The implementation of async_simple is based on libstdc++10 and it is not surprise to me that it can't compile in other versions. Now I see it would use libc++ by default. How can I force it to use libstdc++?

[waruqi]

Currently there is no configuration to explicitly switch to libstdc++, I will improve the configuration to support it, but it may take a while.

[ChuanqiXu9]

Thanks.

[waruqi]

you can try after updating.

add_cxxflags("-stdlib=libstdc++")

[ 76%]: compiling.module.release async_simple:FutureState
[ 76%]: compiling.module.release async_simple:coro.CoAwait
[ 76%]: compiling.module.release async_simple:executors.SimpleExecutor
[ 81%]: compiling.module.release async_simple:Future
[ 81%]: compiling.module.release async_simple:coro.Lazy
[ 84%]: compiling.module.release async_simple:uthread.thread
[ 84%]: compiling.module.release async_simple:coro.Sleep
[ 84%]: compiling.module.release async_simple:coro.Collect
[ 88%]: compiling.module.release async_simple:uthread.Await
[ 88%]: compiling.module.release async_simple:uthread.Uthread
[ 90%]: compiling.module.release async_simple:uthread.Latch
[ 90%]: compiling.module.release async_simple:uthread.Async
[ 93%]: compiling.module.release async_simple:uthread.Collect
[ 94%]: compiling.module.release async_simple
[ 97%]: linking.release libasync_simple.so
[100%]: build ok!

[ChuanqiXu9]

Thanks. It solves my problem.

[waruqi]

and I added libaio package in xmake-repo, we can use it directly.

add_rules("mode.debug", "mode.release")

set_languages("c++20")
add_cxxflags("-stdlib=libstdc++")

add_requires("libaio")

target("std")
    set_kind("static")
    add_files("third_party_module/stdmodules/*.cppm")
    add_includedirs("third_party_module/stdmodules")

target("asio")
    set_kind("static")
    add_files("third_party_module/asio/asio.cppm")
    add_includedirs("third_party_module/asio")

target("async_simple")
    set_kind("static")
    add_files("async_simple_module/*.cppm",
              "async_simple_module/coro/*.cppm",
              "async_simple_module/executors/*.cppm",
              "async_simple_module/uthread/*.cppm",
              "async_simple_module/uthread/internal/*.cppm",
              "async_simple_module/util/*.cppm")
    add_deps("std")
    add_packages("libaio")

[Arthapz]

(you can switch your -stdlib on commandline too xmake f --cxxflags="-stdlib=libstdc++")