how to static link with clang libc++

Question

I just wrote a test code for coroutine in c++2a.

I build the code with clang 5.0 with:

clang++ testcoroutine.cpp -std=c++2a -I../asio_alone -fcoroutines-ts -stdlib=libc++

The code works fine.

Now I want to static link the libc++.so so that I can run the a.out in other PC, I googled but only find the -static-libstdc++.

I can not use the -static-libstdc++ because the libstdc++ does not support the coroutine.

If I use the -static-libstdc++:

clang++ testcoroutine.cpp -std=c++2a -I../asio_alone -fcoroutines-ts
-static-libstdc++ 
testcoroutine.cpp:26:10: fatal error: 'experimental/coroutine' file not found
#include <experimental/coroutine>


 ^~~~~~~~~~~~~~~~~~~~~~~~ 1 error generated.

---

Any suggestion?

---

The test code:

#define ASIO_STANDALONE
#define ASIO_HAS_STD_CHRONO

#ifdef _WIN32
#pragma warning (disable:4819)
#pragma warning (disable:4503)
#pragma warning (disable:4996)
#pragma warning (disable:4100) // unref parameters
#define _CRT_SECURE_NO_WARNINGS
#define NOMINMAX
#define _CRT_NONSTDC_NO_DEPRECATE
#define WIN32_LEAN_AND_MEAN
#endif

#ifdef _WIN32
#include <SDKDDKVer.h>
#endif

#include <stdio.h>
#include <cstdio>
#include <thread>
#include <algorithm>
#include <future>
#include <chrono>
#include <experimental/coroutine>
#include <asio.hpp>

// clang++ testcoroutine.cpp -std=c++2a -I../asio_alone -fcoroutines-ts -stdlib=libc++

#ifndef _WIN32
template <typename... Args>
struct std::experimental::coroutine_traits<std::future<void>, Args...> {
    struct promise_type {
        std::promise<void> p;
        auto get_return_object() { return p.get_future(); }
        std::experimental::suspend_never initial_suspend() { return {}; }
        std::experimental::suspend_never final_suspend() { return {}; }
        void set_exception(std::exception_ptr e) { p.set_exception(std::move(e)); }
        void return_void() { p.set_value(); }
        void unhandled_exception() { std::terminate(); }
    };
};
#endif 

template <typename R, typename P>
auto async_await(asio::steady_timer &t, std::chrono::duration<R, P> d) {
    struct Awaiter {
        asio::steady_timer &t;
        std::chrono::duration<R, P> d;
        asio::error_code ec;

        bool await_ready() { return d.count() == 0; }
        void await_resume() {
            if (ec)
                throw ec;
        }
        void await_suspend(std::experimental::coroutine_handle<> coro) {
            t.expires_from_now(d);
            t.async_wait([this, coro](auto ec) mutable {
                this->ec = ec;
                coro.resume();
            });
        }
    };
    return Awaiter{ t, d };
}


std::future<void> sleepy(asio::io_service &io) {
    asio::steady_timer timer(io);
    co_await async_await(timer, std::chrono::milliseconds(100));
    puts("tick1");
    co_await async_await(timer, std::chrono::milliseconds(100));
    puts("tick2");
    co_await async_await(timer, std::chrono::milliseconds(100));
    puts("tick3");
}

int main()
{      
    asio::io_service io;
    sleepy(io);
    io.run();
    return 0;
}

Answer 1

GNU libstdc++ and LLVM libc++ are two different implementations of the standard C++ library.

Apparently your libstdc++ doesn't yet support the Coroutines TS, so you have to stick to libc++.

To link your application statically just use -static:

clang++ testcoroutine.cpp -std=c++2a -I../asio_alone -fcoroutines-ts -stdlib=libc++ -static

Answer 2

I've encountered a similar issue. After adding the -static flag, I (also) got a large number of "missing symbol" linker errors. In my case, the missing symbols all belonged to the libpthread and libc++abi libraries. Trying to add those library dependencies explicitly in the command line (-lc++abi -pthread) did not help either - this was possibly due to the order in which the default linker used by clang in my system processed the dependencies. Once I switched to the lld linker, the issue seemed to be resolved. All in all, I added the following 4 flags to the clang command: -static -lc++abi -pthread -fuse-ld=lld.