我现在正在尝试 IPC（消息传递）一段时间，但我无法解决这个问题。msgget() 的 errno 22 (EINVAL) 似乎是Invalid message queue identifier, nonpositive message type, or invalid message size。现在， msgrcv() 的 errno 22 是msgqid 无效，或者 msgsz 小于 0，所以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”没问题，因为文档说任何非负返回值都是有效的。有任何想法吗？
将计数器调整为 1 后运行的输出（不想粘贴 100 条错误消息）：
msqID = 0, sendMessage.msgText = Hola!: 0, sendMessage.msgType = 1, MSG_SIZE = 256 Ruh roh, 在父发送中: : 无效参数子 msgrcv(): msqID = 0, rcvMessage.msgText = , rcvMesage.msgType = 1, MSG_SIZE = 256 Ruh roh, in child rcv: : Invalid argument
这在第 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);
}
}