使用重定向的I/O与子进程通信时出现死锁

我正在编写一个程序,以编程方式与自旋模型检查器的交互模块进行通信。为此,我需要重定向spin的i/o,从我的程序启动它,然后重复地读写它。为了进行测试,我使用的是下面的短程序,而不是spin,它只有一个输入和一个输出:

#include <string> 
#include <iostream> 

using std::cin;
using std::cout;
using std::string;

void sprint(string s);
int main() 
{   
    std::string s = "empty";
    cin >> s;
    cout << "\n\tthe text is: " << s;
    return 0;    
} 

我的程序,主要是从 this answer 是:

#include <stdio.h>
#include <stdlib.h>
#include <string>
#include <cstring>
#include <unistd.h>
#include <errno.h>
#include <iostream>

#define PIPE_READ 0
#define PIPE_WRITE 1
#define maxReadSize 2048
using std::cout;
using std::cin;
using std::string;

int createChild(const char* szCommand, const char* aArguments, const char* szMessage);

int main()
{
    createChild("./inout" , "inout", "hello");
    return 0;
}


int createChild(const char* szCommand, const char* aArguments, const char* szMessage) 
{
    int cStdinPipe[2];
    int cStdoutPipe[2];
    int nChild;
    char nChar;
    int nResult;

    if (pipe(cStdinPipe) < 0) 
    { 
        return -1;
    }
    if (pipe(cStdoutPipe) < 0) 
    {
        close(cStdinPipe[PIPE_READ]);
        close(cStdinPipe[PIPE_WRITE]);
        return -1;
    }

    nChild = fork();
    if (0 == nChild) 
    {
        // child continues here
        cout.flush();
        close(cStdinPipe[PIPE_WRITE]);

        // redirect stdin
        if (dup2(cStdinPipe[PIPE_READ], STDIN_FILENO) == -1) 
        {
            exit(errno);
        }

        // redirect stdout
        if (dup2(cStdoutPipe[PIPE_WRITE], STDOUT_FILENO) == -1) 
        {
            exit(errno);
        }

        // all these are for use by parent only
        close(cStdinPipe[PIPE_READ]);
        close(cStdoutPipe[PIPE_READ]);
        close(cStdoutPipe[PIPE_WRITE]); 

        // run child process image
        nResult = execlp(szCommand, aArguments, NULL);

        // if we get here at all, an error occurred, but we are in the child
        // process, so just exit
        exit(nResult);
    } 
    else if (nChild > 0) 
    {
        // parent continues here
        string messageFromChild = "";
        string messageFromParent = "";
        char readBuffer[maxReadSize];
        int bytesWritten = 0;
        int bytesRead = 0;

        // close unused file descriptors, these are for child only
        close(cStdinPipe[PIPE_READ]);
        close(cStdoutPipe[PIPE_WRITE]); 

        // write to child
        if (NULL != szMessage) 
        {
            bytesWritten = write(cStdinPipe[PIPE_WRITE], szMessage, strlen(szMessage));
        }

        // read from child
        bytesRead = read(cStdoutPipe[PIPE_READ], readBuffer, maxReadSize);

        cout << "\nChild says: " << readBuffer << "\n";

        // done with these in this example program, you would normally keep these
        // open of course as long as you want to talk to the child
        close(cStdinPipe[PIPE_WRITE]);
        close(cStdoutPipe[PIPE_READ]);

        std::cout << "\n\nParent ending";
    } 
    else 
    {
        // failed to create child
        close(cStdinPipe[PIPE_READ]);
        close(cStdinPipe[PIPE_WRITE]);
        close(cStdoutPipe[PIPE_READ]);
        close(cStdoutPipe[PIPE_WRITE]);
    }
    return nChild;
}

运行此程序会导致死锁,而子进程将卡在 cin 和父母在一起 read() 是的。删除这些调用中的任何一个都会导致程序运行到终止并正常退出。 write() 和 cout 两者都能正常工作。