Windows WSL2 Ubuntu下VSCode配置Boost库编译报错求助

环境与安装情况 #

• Windows 10 WSL2 Ubuntu 20.04环境，VSCode全新配置
• 已通过sudo apt-get install libboost-all-dev安装Boost全量库
• g环境配置完成，可正常编译运行基础C程序

配置的tasks.json文件 #

{
  "tasks": [
    {
        "type": "cppbuild",
        "label": "C/C++: g++ build active file",
        "command": "/usr/bin/g++",
        "args": [
            "-fdiagnostics-color=always",
            "-g",
            "-I/usr/local/include",
            "-L/usr/local/lib",
            "-lboost_system",
            "${file}",
            "-o",
            "${fileDirname}/${fileBasenameNoExtension}"
        ],
        "options": {
            "cwd": "${fileDirname}"
        },
        "problemMatcher": [
            "$gcc"
        ],
        "group": {
            "kind": "build",
            "isDefault": true
        },
        "detail": "Task generated by Debugger."
    }
],
  "version": "2.0.0"
}

代码头文件引用（Linter无报错） #

#include <boost/beast/core.hpp>
#include <boost/beast/websocket.hpp>
#include <boost/asio/connect.hpp>
#include <boost/asio/ip/tcp.hpp>
using tcp = boost::asio::ip::tcp;
namespace websocket = boost::beast::websocket;

编译错误信息 #

Starting build...
/usr/bin/g++ -fdiagnostics-color=always -g -I/usr/local/include -L/usr/local/lib -lboost_system /home/laptop/cppbot/helloworld.cpp -o /home/laptop/cppbot/helloworld
/usr/bin/ld: /tmp/ccmv4tdX.o: in function `boost::asio::detail::posix_event::posix_event()':
/usr/include/boost/asio/detail/impl/posix_event.ipp:42: undefined reference to `pthread_condattr_setclock'
/usr/bin/ld: /tmp/ccmv4tdX.o: in function `boost::asio::detail::posix_thread::~posix_thread()':
/usr/include/boost/asio/detail/impl/posix_thread.ipp:35: undefined reference to `pthread_detach'
/usr/bin/ld: /tmp/ccmv4tdX.o: in function `boost::asio::detail::posix_thread::join()':
/usr/include/boost/asio/detail/impl/posix_thread.ipp:42: undefined reference to `pthread_join'
/usr/bin/ld: /tmp/ccmv4tdX.o: in function `boost::asio::detail::posix_thread::start_thread(boost::asio::detail::posix_thread::func_base*)':
/usr/include/boost/asio/detail/impl/posix_thread.ipp:59: undefined reference to `pthread_create'
/usr/bin/ld: /tmp/ccmv4tdX.o: in function `boost::asio::detail::posix_signal_blocker::posix_signal_blocker()':
/usr/include/boost/asio/detail/posix_signal_blocker.hpp:43: undefined reference to `pthread_sigmask'
/usr/bin/ld: /tmp/ccmv4tdX.o: in function `boost::asio::detail::posix_signal_blocker::~posix_signal_blocker()':
/usr/include/boost/asio/detail/posix_signal_blocker.hpp:50: undefined reference to `pthread_sigmask'
collect2: error: ld returned 1 exit status

解决方案 #

错误根源是Boost.Asio依赖POSIX线程库（pthread），但当前编译命令未链接该库，同时存在库链接顺序错误。需修改tasks.json的编译参数：

1. 添加-pthread参数以链接pthread库
2. 调整库参数顺序：源文件${file}必须放在-lboost_system等库参数之前（g++链接器按顺序解析符号，后出现的库无法为前面的目标文件提供符号）

修改后的tasks.json关键部分：

"args": [
    "-fdiagnostics-color=always",
    "-g",
    "-I/usr/local/include",
    "-L/usr/local/lib",
    "${file}",
    "-o",
    "${fileDirname}/${fileBasenameNoExtension}",
    "-lboost_system",
    "-pthread"
]

内容的提问来源于stack exchange，提问作者Pearl