C++ waitpid的早期调用未正确收集退出状态

我使用下面的代码来分叉一个进程，并向它发出信号，让它稍后停止

#include <unistd.h>
#include <stdlib.h>
#include <sys/wait.h>
#include <sys/types.h>
#include <iostream>

using namespace std;

sig_atomic_t stopFlag = 0;
void measurementSignalHandler(int sig) {
  stopFlag = 1;
}

int main(int argc, char **argv) {
  pid_t measurementPid = fork();

  switch(measurementPid) {
  case -1:
    // fork failed
    cerr << "Failed to create measurement process." << endl;
    exit(1);
  case 0:
    // child
    signal(SIGUSR1, measurementSignalHandler);
    while(stopFlag == 0) {
      sleep(1);
    }

    cout << "Done with measurements." << endl;
    return 42;
  default:
    // parent
    sleep(5);

    // I do not understand why this sleep is necessary.
    kill(measurementPid, SIGUSR1);
    cout << "Giving measurement process some time to clean up."
         << endl;
    sleep(3);

    int childExitStatus;
    waitpid(measurementPid, &childExitStatus, 1);
    if(WIFEXITED(childExitStatus)) {
      cout << "Measurement process returned "
           << WEXITSTATUS(childExitStatus)
           << "." << endl;
    }
    else if(WIFSIGNALED(childExitStatus)) {
      cout << "Measurement process was terminated by signal "
           << WTERMSIG(childExitStatus)
           << "." << endl;
    }
    else {
      cout << "Measurement process ended neither on its own "
           << "nor by signal." << endl;
    }

    return 0;
  }
}

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使用名称空间std；
sig_原子停止标志=0；
无效度量信号处理器（int sig）{
stopFlag=1；
}
int main（int argc，字符**argv）{
pid_t measurementPid=fork（）；
开关（测量ID）{
案例1：
//fork失败了
cerr您正在将1传递给
waitpid
。我猜1是
WAITNOHANG
，这意味着它不会等到所有子项都完成。谢谢，RedX，这似乎解决了这个问题。这个错误是由于只扫描手册页而没有仔细阅读详细信息造成的。