c – fork()和execv()之后的QProcess问题

我使用fork()和execv()来启动工作进程.

问题是QProcess仅在第一个工作进程中成功完成.生成新的工作进程后,QProcess永远不会说它已完成.触摸命令本身一直都很好.但是在除了第一个工作流程之外的所有工作流程中,它最终变成了僵尸.

这是一个最小的测试程序：

#include <QCoreApplication>
#include <QProcess>
#include <QDebug>

#include <signal.h>
#include <wait.h>

void spawnWorkerProcess();
void launchQProcess();
void catchSigChild(int i);
void execChild();

int main(int argc,char *argv[])
{
    QCoreApplication app(argc,argv);

    if (argc > 1) // worker process
    {
        launchQProcess();
    }
    else // main process
    {
        if (signal(SIGCHLD,catchSigChild) == SIG_ERR)
        {
            qFatal("could not attach to SIGCHLD");
        }

        spawnWorkerProcess();

        return app.exec();
    }
}

void spawnWorkerProcess()
{
    pid_t pid = fork();
    if (pid == -1)
    {
        qCritical() << "FORK ERROR";
        exit(1);
    }
    else if (pid == 0)
    {
        /* the child process */
        execChild();
        exit(1);
    }
    else
    {
        qWarning() << "FORK OK";
    }
}


void
execChild()
{
    unsigned i = 0;
    const char **argv = new const char *[3];

    QByteArray ba = qApp->applicationFilePath().toLocal8Bit();
    argv[i++] = ba.data();
    argv[i++] = "worker";
    argv[i++] = 0;

    qWarning() << "execv ..."  << argv;
    execv(argv[0],const_cast<char *const *>(argv));
    qWarning() << "execv OK";

    delete[] argv;
}

void catchSigChild(int i)
{
    qCritical() << Q_FUNC_INFO << i;

    pid_t cpid;
    int stat;

    while ((cpid = waitpid(0,&stat,WNOHANG)) > 0)
    {
        static int counter = 0;

        counter++;

        if (counter < 5)
        {
            qDebug() << "SPAWN:" << counter;
            spawnWorkerProcess();
        }
        else
        {
            qCritical() << "RESPAWN LIMIT REACHED! Bye-bye!";
            exit(0);
        }
    }
}
void
launchQProcess()
{
    QProcess pr;

    qWarning() << "start QProcess " << qApp->applicationPid();
    pr.start(QString("touch /tmp/test/%1").arg(qApp->applicationPid()),0);

    if (! pr.waitForFinished(3000))
    {
        qWarning() << "QProcess FAIL" << qApp->applicationPid() << pr.state() << "n";

        delete (int*) 1; // we don't want to wait for QProcess timeout,so doing crash
    }
    else
    {
        qWarning() << "QProcess OK" << qApp->applicationPid() << pr.state() << "n";
    }
}