Question

我已经阅读了我的问题的早期问题和答案，但是大多数人似乎都在使用shmget而不是mmap。

我正在使用mmap作为共享内存，它一切正常，直到我从使用静态变量更改为结构。目前，我收到以下错误：

<project>
  <echo message="Hello!"/>
  <groovy> <!-- Would be nice if I could treat this like a built-in -->
    println "Hello from Groovy!"
  </groovy>
</project>

我理解错误，但是我不确定如何使用结构来解决它，因为这是我认为共享内存完成的方式。我正在分叉，所以这些结构正在儿童过程中使用。

我的代码：

server.c: In function ‘interfaceComms’:
server.c:129:18: error: ‘interfaceConnection’ undeclared (first use in this function)
  n = write(sock, interfaceConnection->processingResults, 47);
                  ^
server.c:129:18: note: each undeclared identifier is reported only once for each function it appears in
server.c:139:12: error: ‘imageDetails’ undeclared (first use in this function)
  if(strcmp(imageDetails->prevImage, "") != 0) {
            ^
server.c: In function ‘robotComms’:
server.c:162:2: error: ‘imageDetails’ undeclared (first use in this function)
  imageDetails->prevImage = imageDetails->currImage;
  ^
server.c:213:9: error: ‘interfaceConnection’ undeclared (first use in this function)
  strcpy(interfaceConnection->processingResults, msg);

功能＆＃39; interfaceComms＆＃39;和＆＃39; robotComms＆＃39;在fork发生后稍后调用。但我猜测我的问题就在那里。

根据要求，intefaceComms和robotComms功能：

typedef struct Images {
    char prevImage;
    char currImage;
} image;

typedef struct Robot {
    char coordinates;
} robot;

typedef struct Interface {
    char processingResults;
} interface;

int main(int argc, char *argv[]){
int sockfd, newsockfd, portno, clilen, memid;
char buffer[256];
struct sockaddr_in serv_addr, cli_addr;
int n, pid;
interface *interfaceConnection;
image *imageDetails;

// First call to socket() function
sockfd = socket(AF_INET, SOCK_STREAM, 0);

if (sockfd < 0){
    perror("Error opening socket");
    exit(1);
}

// Initialise socket structure
bzero((char *) &serv_addr, sizeof(serv_addr));
portno = 5001;

serv_addr.sin_family = AF_INET;
serv_addr.sin_addr.s_addr = INADDR_ANY;
serv_addr.sin_port = htons(portno);

//Bind the socket
if(bind(sockfd, (struct sockaddr *) &serv_addr, sizeof(serv_addr)) < 0){
    perror("Error binding socket");
    exit(1);
}

//Listen for client connections
listen(sockfd,5);
clilen = sizeof(cli_addr);

//Share memory before forking
interfaceConnection = mmap(NULL, sizeof(interface), PROT_READ | PROT_WRITE, 
                MAP_SHARED | MAP_ANONYMOUS, -1, 0);

imageDetails = mmap(NULL, sizeof(image), PROT_READ | PROT_WRITE, 
            MAP_SHARED | MAP_ANONYMOUS, -1, 0);

提前致谢。

Answer 1

您的问题是interfaceConnection是主函数中的局部变量。

interface *interfaceConnection;

我假设您希望在全球范围内使用此功能。没有看到其他代码就很难分辨。

使用mmap在C中共享内存中的结构

1 个答案: