c - C Linux(Ubuntu)-msgsnd()和msgrcv()errno 22(EINVAL)

我在ipc（消息传递）上试了一会儿，但我无法解决这个问题。msgget（）的errno 22（einval）似乎是无效的消息队列标识符、非正消息类型或无效的消息大小。现在，msgrcv（）的errno 22是msgqid invalid，或者msgsz小于0，因此这似乎表明我的队列id是错误的，因为无效的msqueue id在两个错误解释中重叠。
我应该注意，我的msgget（）调用返回0作为队列ID。这应该很好，因为文档中说任何非负的返回值都是有效的。有什么想法吗？
将计数器调整为1后运行的输出（不希望粘贴100条错误消息）：
msqid=0，sendmessage.msgtext=hola！：0，sendmessage.msgtype=1，msg_size=256 ruh roh，在父send：：无效参数中
子msgrcv（）：msqid=0，rcvmessage.msgtext=，rcvmessage.msgtype=1，msg_size=256
ruh roh，in child rcv：：无效参数
在第31行（父进程中的第一个msgsnd（））和第60行（子进程中的第一个msgrcv（））上失败。

#include <errno.h>
#include <sys/msg.h>
#include <sys/ipc.h>
#include <time.h>
#include <stdlib.h>
#include <unistd.h>
#include <string.h>
#include <stdio.h>
#include <math.h>
const int MAX_TEXT_SIZE = 255;
const int COUNTER = 99;
int main(){
  srand(time(NULL));
  int childPID, key = rand(), msgSendRslt, msgRecvRslt, msqID;
  long int type  = 1;
  struct msg {long msgType; char msgText[MAX_TEXT_SIZE];};
  const int MSG_SIZE = sizeof(struct msg)-sizeof(long int);
    if(msqID = msgget(key, IPC_CREAT | 0666) == -1){
      perror("\nRuh roh: ");
      exit(1);
    }
    if((childPID = fork()) > 0){
      struct msg sendMessage, rcvMessage;
      sendMessage.msgType = type;
      char *sendMsg = malloc(MAX_TEXT_SIZE);
      for(int i = 0; i < 100; i++){
        sprintf(sendMsg, "Hola!: %d", i);
        strcpy(sendMessage.msgText, sendMsg);
        printf("\nmsqID = %d, sendMessage.msgText = %s, sendMessage.msgType = %ld, MSG_SIZE = %d", msqID, sendMessage.msgText, sendMessage.msgType, MSG_SIZE);
        printf("\n");
        if(msgsnd(msqID, &sendMsg, MSG_SIZE, IPC_NOWAIT) != -1){
          printf("\nFrom parent, sent msg %d", i);
          if(msgrcv(msqID, &rcvMessage, MSG_SIZE, rcvMessage.msgType, IPC_NOWAIT) != -1){;
            printf("\nIn the parent, received from child: %s", rcvMessage.msgText);
          }
          else
            perror("\nRuh roh, in parent rcv: ");
        }
        else
          perror("\nRuh roh, in parent send: ");
          printf("\nerrno: %d", errno);
      }
      strcpy(sendMessage.msgText, "Over and out!");
      if(msgsnd(msqID, &sendMsg, MSG_SIZE, 0) == -1)
        perror("\nRuh roh, in parent send at end: ");
    }
  else if (childPID == 0){ //child
    int count = 0;
    int test = ceil(3.8);
    char *countS = malloc(ceil(log(COUNTER)/log(10)));
    struct msg rcvMessage, sendMessage;
    strcpy(rcvMessage.msgText, "");
    sendMessage.msgType = type;
    rcvMessage.msgType = type;
    while(strcmp(rcvMessage.msgText, "Over and out!") != 0){
      sprintf(countS, "%d", count);
      strcat(strcpy(sendMessage.msgText, "10-4 good buddy!: "), countS);
      printf("\nchild msgrcv(): msqID = %d, rcvMessage.msgText = %s, rcvMesage.msgType = %ld, MSG_SIZE = %d", msqID, rcvMessage.msgText, rcvMessage.msgType, MSG_SIZE);
      printf("\n");
      if(msgrcv(msqID, &rcvMessage, MSG_SIZE, rcvMessage.msgType, IPC_NOWAIT) != -1){
        printf("\nIn the child, received from the parent: %s", rcvMessage.msgText);
        if(msgsnd(msqID, &sendMessage, MSG_SIZE, IPC_NOWAIT) == -1)
          perror("\nRuh roh, in child send: ");
          exit(1);
      }
      else
        perror("Ruh roh, in child rcv: ");
        printf("\nChild error: %d", errno);
        exit(1);
    }
  }
  else{
    perror("\nRuh roh, fork() problem: ");
    printf("\n");
    exit(1);
  }
}

最佳答案

我盯着你的代码看了这么久才发现问题。

if(msqID = msgget(key, IPC_CREAT | 0666) == -1)

括号放错地方了！该代码有效地将msgget(key, IPC_CREAT | 0666) == -1分配给msqID。也就是说，msqID是条件的结果，并解释了为什么msqID总是0。
正确的代码如下。注意括号的位置。

if((msqID = msgget(key, IPC_CREAT | 0666)) == -1)

关于c - C Linux(Ubuntu)-msgsnd()和msgrcv()errno 22(EINVAL)，我们在Stack Overflow上找到一个类似的问题：https://stackoverflow.com/questions/33925120/