无法从提升子进程中获取分段错误退出代码

Question

我正在尝试获取子进程的退出代码（使用 boost::process 和 boost::asio），当该子进程由于分段违规或除数为零或任何其他终止而被终止时信号。退出代码和错误代码总是 return 0 和成功。

我运行在 CentOS 7 上使用 g++ 4.8.5 和 boost 1.66

如果我运行具有子进程的相同代码只是 return 一个非零退出代码它成功 return 那个退出代码。

#include <iostream>
#include <boost/process.hpp>
#include <boost/asio/io_service.hpp>

namespace bp = boost::process;
using namespace std;

int main (int argc, char** argv)
{
   string exe = "./crashes";

   vector<string> data;
   boost::asio::io_service ios;

   int exit_code;
   error_code ec;
   future<string> ostr;

   bp::child c(exe,
               (bp::std_out & bp::std_err) > ostr,
               ios,
               bp::on_exit=[&exit_code, &ec](int exit, const error_code& ecin)
                                             {exit_code = exit; ec = ecin;});

   ios.run();

   cout << "Exit Code = " << exit_code << endl;
   cout << "Error Code = " << ec.message() << endl;
   cout << "child stdin & stderr:\n";
   cout << ostr.get() << endl;
   return exit_code;
}

和崩溃代码

int main (int argc, char** argv)
{
   int* y = 0;
   int c = *y;
}

结果显示 0 退出代码和成功 error_code

Exit Code = 0
Error Code = Success
child stdin & stderr:

运行单独使用崩溃可执行文件return退出代码 139

bash-4.2$ ./crashes 
Segmentation fault (core dumped)
bash-4.2$ echo $?
139

Answer 1

进程终止和退出代码的详细信息取决于平台。

Boost 进程介绍了默认界面中的差异：您的 on_exit 处理程序被调用，退出状态的结果为 boost::process::detail::posix::eval_exit_status()，这意味着：

inline int eval_exit_status(int code)
{
    if (WIFEXITED(code))
    {
        return WEXITSTATUS(code);
    }
    else if (WIFSIGNALED(code))
    {
        return WTERMSIG(code);
    }
    else
    {
        return code;
    }
}

所以，你得到 "exit-code 11" 意思是段错误......如果你想真正知道，你可以看看 native_exit_code()

bp::on_exit = [&result, &c](int /*ignored*/, const std::error_code &ec) {
    auto exit_status = c.native_exit_code();
    result.exit_code = boost::make_optional(WIFEXITED(exit_status), WEXITSTATUS(exit_status));
    result.signal    = boost::make_optional(WIFSIGNALED(exit_status), WTERMSIG(exit_status));
    result.ec = ec;
}

现在假设对结果变量进行了一些更改。完整列表：

列表

#include <boost/asio/io_service.hpp>
#include <boost/process.hpp>
#include <iostream>

namespace bp = boost::process;

int main(int argc, char**) {
    std::string exe = argc>1? "./ltua" : "./crashes";

    boost::asio::io_service ios;

    struct {
        boost::optional<int> exit_code;
        boost::optional<int> signal;
        std::error_code ec{};
    } result;

    std::future<std::string> ostr;

    bp::group g;
    bp::child c(exe, g, (bp::std_out & bp::std_err) > ostr, ios,
        bp::on_exit = [&result, &c](int /*ignored*/, const std::error_code &ec) {
            auto exit_status = c.native_exit_code();
            result.exit_code = boost::make_optional(WIFEXITED(exit_status), WEXITSTATUS(exit_status));
            result.signal    = boost::make_optional(WIFSIGNALED(exit_status), WTERMSIG(exit_status));
            result.ec = ec;
        });

    //g.wait();
    ios.run();

    if (result.exit_code) {
        std::cout << "Exited with " << *result.exit_code << std::endl;
    }
    if (result.signal) {
        std::cout << "Signaled with sginal #" << *result.signal << ", aka " << ::strsignal(*result.signal) <<  std::endl;
    }

    std::cout << "Error Code = " << result.ec.message() << std::endl;
    std::cout << "child stdin & stderr:\n";
    std::cout << ostr.get() << std::endl;
    return result.exit_code? *result.exit_code : 255;
}

输出

当运行与 ltua.cpp:

#include <iostream>
int main() {
    std::cout << "so  long"   << std::end;
    std::cerr << "and thanks" << std::end;
    std::cout << "for all"    << std::end;
    std::cerr << "the fish"   << std::end;
    return 42;
}

版画

Exited with 42
Error Code = Success
child stdin & stderr:
so  long
and thanks
for all
the fish

与 crashes.cpp:

int main() {
    int *y = 0;
    int c = *y;
}

版画

Signaled with sginal #11, aka Segmentation fault
Error Code = Success
child stdin & stderr:

无法从提升子进程中获取分段错误退出代码

Can't get segmentation fault exit code from boost child process

c++11

boost-asio

boost-process

列表

输出