Question:
I am learning boost asio now. When I try to compile its example code on ubuntu18.04 with CMake, I use the clang toolset. I got a link error.
undefined reference to symbol '_ZNSt3__15mutex4lockEv'
But if I try to use the clang++ command to compile it instead, it goes well.
clang++ -std=c++2a -stdlib=libc++ -v -fcoroutines-ts -lpthread test.cpp -o test
test.cpp file:
#include <boost/asio/co_spawn.hpp>
#include <boost/asio/detached.hpp>
#include <boost/asio/io_context.hpp>
#include <boost/asio/ip/tcp.hpp>
#include <boost/asio/signal_set.hpp>
#include <boost/asio/write.hpp>
#include <cstdio>
using boost::asio::awaitable;
using boost::asio::co_spawn;
using boost::asio::detached;
using boost::asio::use_awaitable;
using boost::asio::ip::tcp;
namespace this_coro = boost::asio::this_coro;
awaitable<void> echo(tcp::socket socket) {
try {
char data[1024];
for (;;) {
std::size_t n = co_await socket.async_read_some(boost::asio::buffer(data),
use_awaitable);
co_await async_write(socket, boost::asio::buffer(data, n), use_awaitable);
}
} catch (std::exception &e) {
std::printf("echo Exception: %s\n", e.what());
}
}
awaitable<void> listener() {
auto executor = co_await this_coro::executor;
tcp::acceptor acceptor(executor, {tcp::v4(), 55555});
for (;;) {
tcp::socket socket = co_await acceptor.async_accept(use_awaitable);
co_spawn(
executor,
[socket = std::move(socket)]() mutable {
return echo(std::move(socket));
},
detached);
}
}
int main() {
try {
boost::asio::io_context io_context(1);
boost::asio::signal_set signals(io_context, SIGINT, SIGTERM);
signals.async_wait([&](auto, auto) { io_context.stop(); });
co_spawn(io_context, listener, detached);
io_context.run();
} catch (std::exception &e) {
std::printf("Exception: %s\n", e.what());
}
}
CMakeLists.txt:
project(learn)
cmake_minimum_required(VERSION 3.11)
find_package(Boost 1.72.0 COMPONENTS fiber context thread)
if(Boost_FOUND)
set(Boost_USE_MULTITHREAD ON)
include_directories(${Boost_INCLUDE_DIRS})
link_libraries(${Boost_LIBRARIES})
endif()
if(MSVC)
set(CMAKE_CXX_STANDARD 17)
add_compile_options(/await)
else()
add_compile_options("-std=c++2a" "-stdlib=libc++" "-v" "-fcoroutines-ts")
endif()
#add_executable(learn_asio learn_asio.cpp)
add_executable(test test.cpp)
compilation output:
cd /mnt/e/c++/learn/out/build/WSL-Clang-Debug;export CFLAGS=-fno-limit-debug-info;export CXXFLAGS=-fno-limit-debug-info;/usr/bin/cmake --build /mnt/e/c++/learn/out/build/WSL-Clang-Debug --clean-first ;
[ 50%] Building CXX object CMakeFiles/test.dir/test.cpp.o
clang version 9.0.0-2~ubuntu18.04.2 (tags/RELEASE_900/final)
Target: x86_64-pc-linux-gnu
Thread model: posix
InstalledDir: /usr/bin
Found candidate GCC installation: /usr/bin/../lib/gcc/x86_64-linux-gnu/7
Found candidate GCC installation: /usr/bin/../lib/gcc/x86_64-linux-gnu/7.4.0
Found candidate GCC installation: /usr/bin/../lib/gcc/x86_64-linux-gnu/8
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/7
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/7.4.0
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/8
Selected GCC installation: /usr/bin/../lib/gcc/x86_64-linux-gnu/7.4.0
Candidate multilib: .;@m64
Selected multilib: .;@m64
"/usr/lib/llvm-9/bin/clang" -cc1 -triple x86_64-pc-linux-gnu -emit-obj -mrelax-all -disable-free -disable-llvm-verifier -discard-value-names -main-file-name test.cpp -mrelocation-model static -mthread-model posix -mdisable-fp-elim -fmath-errno -masm-verbose -mconstructor-aliases -munwind-tables -fuse-init-array -target-cpu x86-64 -dwarf-column-info -debug-info-kind=standalone -dwarf-version=4 -debugger-tuning=gdb -v -coverage-notes-file /mnt/e/c++/learn/out/build/WSL-Clang-Debug/CMakeFiles/test.dir/test.cpp.gcno -resource-dir /usr/lib/llvm-9/lib/clang/9.0.0 -D BOOST_ALL_NO_LIB -D BOOST_CONTEXT_DYN_LINK -D BOOST_FIBER_DYN_LINK -D BOOST_FILESYSTEM_DYN_LINK -D BOOST_THREAD_DYN_LINK -internal-isystem /usr/lib/llvm-9/bin/../include/c++/v1 -internal-isystem /usr/local/include -internal-isystem /usr/lib/llvm-9/lib/clang/9.0.0/include -internal-externc-isystem /usr/include/x86_64-linux-gnu -internal-externc-isystem /include -internal-externc-isystem /usr/include -std=c++2a -fdeprecated-macro -fdebug-compilation-dir /mnt/e/c++/learn/out/build/WSL-Clang-Debug -ferror-limit 19 -fmessage-length 0 -fcoroutines-ts -fno-implicit-modules -fobjc-runtime=gcc -fcxx-exceptions -fexceptions -fdiagnostics-show-option -faddrsig -o CMakeFiles/test.dir/test.cpp.o -x c++ /mnt/e/c++/learn/test.cpp
clang -cc1 version 9.0.0 based upon LLVM 9.0.0 default target x86_64-pc-linux-gnu
ignoring nonexistent directory "/include"
#include "..." search starts here:
#include <...> search starts here:
/usr/lib/llvm-9/bin/../include/c++/v1
/usr/local/include
/usr/lib/llvm-9/lib/clang/9.0.0/include
/usr/include/x86_64-linux-gnu
/usr/include
End of search list.
[100%] Linking CXX executable test
/usr/bin/ld: CMakeFiles/test.dir/test.cpp.o: undefined reference to symbol '_ZNSt3__15mutex4lockEv'
//usr/lib/x86_64-linux-gnu/libc++.so.1: error adding symbols: DSO missing from command line
clang: error: linker command failed with exit code 1 (use -v to see invocation)
CMakeFiles/test.dir/build.make:87: recipe for target 'test' failed
make[2]: *** [test] Error 1
CMakeFiles/Makefile2:75: recipe for target 'CMakeFiles/test.dir/all' failed
make[1]: *** [CMakeFiles/test.dir/all] Error 2
Makefile:83: recipe for target 'all' failed
make: *** [all] Error 2
link error:
/usr/bin/ld: CMakeFiles/test.dir/test.cpp.o: undefined reference to symbol '_ZNSt3__15mutex4lockEv'
//usr/lib/x86_64-linux-gnu/libc++.so.1: error adding symbols: DSO missing from command line
clang: error: linker command failed with exit code 1 (use -v to see invocation)
