关于游双Linux高性能服务器编程代码清单13-4 Segmentation fault (core dumped)报错问题
我尝试了各种改编的或者官方的代码，居然都是错的，最终我发现了问题在于这一行代码
sub_process[pid] = user_count;
就是这行代码把pid赋予数组，但是这个数组有多大呢，代码如下
sub_process = new int[PROCESS_LIMIT ];
会发现代码最大才65536显然比pid号码要小，所以*100就行了改为如下代码，如果100还不行就1000或者更大
sub_process = new int[PROCESS_LIMIT * 100];
我修改后官方代码清单13-4代码如下，我测试过，是可以运行的，也不会报错了。
#include
#include
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#include
#include
#include
#define USER_LIMIT 5
#define BUFFER_SIZE 1024
#define FD_LIMIT 65535
#define MAX_EVENT_NUMBER 1024
#define PROCESS_LIMIT 65536
struct client_data
{
sockaddr_in address;
int connfd;
pid_t pid;
int pipefd[2];
};
static const char *shm_name = "/my_shm";
int sig_pipefd[2];
int epollfd;
int listenfd;
int shmfd;
char *share_mem = 0;
client_data *users = 0;
int *sub_process = 0;
int user_count = 0;
bool stop_child = false;
int setnonblocking(int fd)
{
int old_option = fcntl(fd, F_GETFL);
int new_option = old_option | O_NONBLOCK;
fcntl(fd, F_SETFL, new_option);
return old_option;
}
void addfd(int epollfd, int fd)
{
epoll_event event;
event.data.fd = fd;
event.events = EPOLLIN | EPOLLET;
epoll_ctl(epollfd, EPOLL_CTL_ADD, fd, &event);
setnonblocking(fd);
}
void sig_handler(int sig)
{
int save_errno = errno;
int msg = sig;
send(sig_pipefd[1], (char *) &msg, 1, 0);
errno = save_errno;
}
void addsig(int sig, void (*handler)(int), bool restart = true)
{
struct sigaction sa;
memset(&sa, '\0', sizeof(sa));
sa.sa_handler = handler;
if (restart)
{
sa.sa_flags |= SA_RESTART;
}
sigfillset(&sa.sa_mask);
assert(sigaction(sig, &sa, NULL) != -1);
}
void del_resource()
{
close(sig_pipefd[0]);
close(sig_pipefd[1]);
close(listenfd);
close(epollfd);
shm_unlink(shm_name);
delete[] users;
delete[] sub_process;
}
void child_term_handler(int sig)
{
stop_child = true;
}
int run_child(int idx, client_data *users, char *share_mem)
{
epoll_event events[MAX_EVENT_NUMBER];
int child_epollfd = epoll_create(5);
assert(child_epollfd != -1);
int connfd = users[idx].connfd;
addfd(child_epollfd, connfd);
int pipefd = users[idx].pipefd[1];
addfd(child_epollfd, pipefd);
int ret;
addsig(SIGTERM, child_term_handler, false);
while (!stop_child)
{
int number = epoll_wait(child_epollfd, events, MAX_EVENT_NUMBER, -1);
if ((number < 0) && (errno != EINTR))
{
printf("epoll failure\n");
break;
}
for (int i = 0; i < number; i++)
{
int sockfd = events[i].data.fd;
if ((sockfd == connfd) && (events[i].events & EPOLLIN))
{
memset(share_mem + idx * BUFFER_SIZE, '\0', BUFFER_SIZE);
ret = recv(connfd, share_mem + idx * BUFFER_SIZE, BUFFER_SIZE - 1, 0);
if (ret < 0)
{
if (errno != EAGAIN)
{
stop_child = true;
}
}
else if (ret == 0)
{
stop_child = true;
}
else
{
send(pipefd, (char *) &idx, sizeof(idx), 0);
}
}
else if ((sockfd == pipefd) && (events[i].events & EPOLLIN))
{
int client = 0;
ret = recv(sockfd, (char *) &client, sizeof(client), 0);
if (ret < 0)
{
if (errno != EAGAIN)
{
stop_child = true;
}
}
else if (ret == 0)
{
stop_child = true;
}
else
{
send(connfd, share_mem + client * BUFFER_SIZE, BUFFER_SIZE, 0);
}
}
else
{
continue;
}
}
}
close(connfd);
close(pipefd);
close(child_epollfd);
return 0;
}
int main(int argc, char *argv[])
{
if (argc <= 2)
{
printf("usage: %s ip_address port_number\n", basename(argv[0]));
return 1;
}
const char *ip = argv[1];
int port = atoi(argv[2]);
int ret = 0;
struct sockaddr_in address;
bzero(&address, sizeof(address));
address.sin_family = AF_INET;
inet_pton(AF_INET, ip, &address.sin_addr);
address.sin_port = htons(port);
listenfd = socket(PF_INET, SOCK_STREAM, 0);
assert(listenfd >= 0);
ret = bind(listenfd, (struct sockaddr *) &address, sizeof(address));
assert(ret != -1);
ret = listen(listenfd, 5);
assert(ret != -1);
user_count = 0;
users = new client_data[USER_LIMIT + 1];
sub_process = new int[PROCESS_LIMIT * 10];
for (int i = 0; i < PROCESS_LIMIT; ++i)
{
sub_process[i] = -1;
}
epoll_event events[MAX_EVENT_NUMBER];
epollfd = epoll_create(5);
assert(epollfd != -1);
addfd(epollfd, listenfd);
ret = socketpair(PF_UNIX, SOCK_STREAM, 0, sig_pipefd);
assert(ret != -1);
setnonblocking(sig_pipefd[1]);
addfd(epollfd, sig_pipefd[0]);
addsig(SIGCHLD, sig_handler);
addsig(SIGTERM, sig_handler);
addsig(SIGINT, sig_handler);
addsig(SIGPIPE, SIG_IGN);
bool stop_server = false;
bool terminate = false;
shmfd = shm_open(shm_name, O_CREAT | O_RDWR, 0666);
assert(shmfd != -1);
ret = ftruncate(shmfd, USER_LIMIT * BUFFER_SIZE);
assert(ret != -1);
share_mem = (char *) mmap(NULL, USER_LIMIT * BUFFER_SIZE, PROT_READ | PROT_WRITE, MAP_SHARED, shmfd, 0);
assert(share_mem != MAP_FAILED);
close(shmfd);
while (!stop_server)
{
int number = epoll_wait(epollfd, events, MAX_EVENT_NUMBER, -1);
if ((number < 0) && (errno != EINTR))
{
printf("epoll failure\n");
break;
}
for (int i = 0; i < number; i++)
{
int sockfd = events[i].data.fd;
if (sockfd == listenfd)
{
struct sockaddr_in client_address;
socklen_t client_addrlength = sizeof(client_address);
int connfd = accept(listenfd, (struct sockaddr *) &client_address, &client_addrlength);
if (connfd < 0)
{
printf("errno is: %d\n", errno);
continue;
}
if (user_count >= USER_LIMIT)
{
const char *info = "too many users\n";
printf("%s", info);
send(connfd, info, strlen(info), 0);
close(connfd);
continue;
}
users[user_count].address = client_address;
users[user_count].connfd = connfd;
ret = socketpair(PF_UNIX, SOCK_STREAM, 0, users[user_count].pipefd);
assert(ret != -1);
pid_t pid = fork();
if (pid < 0)
{
close(connfd);
continue;
}
else if (pid == 0)
{
close(epollfd);
close(listenfd);
close(users[user_count].pipefd[0]);
close(sig_pipefd[0]);
close(sig_pipefd[1]);
run_child(user_count, users, share_mem);
munmap((void *) share_mem, USER_LIMIT * BUFFER_SIZE);
exit(0);
}
else
{
close(connfd);
close(users[user_count].pipefd[1]);
addfd(epollfd, users[user_count].pipefd[0]);
users[user_count].pid = pid;
sub_process[pid] = user_count;
user_count++;
}
}
else if ((sockfd == sig_pipefd[0]) && (events[i].events & EPOLLIN))
{
int sig;
char signals[1024];
ret = recv(sig_pipefd[0], signals, sizeof(signals), 0);
if (ret == -1)
{
continue;
}
else if (ret == 0)
{
continue;
}
else
{
for (int i = 0; i < ret; ++i)
{
switch (signals[i])
{
case SIGCHLD:
{
pid_t pid;
int stat;
while ((pid = waitpid(-1, &stat, WNOHANG)) > 0)
{
int del_user = sub_process[pid];
sub_process[pid] = -1;
if ((del_user < 0) || (del_user > USER_LIMIT))
{
printf("the deleted user was not change\n");
continue;
}
epoll_ctl(epollfd, EPOLL_CTL_DEL, users[del_user].pipefd[0], 0);
close(users[del_user].pipefd[0]);
users[del_user] = users[--user_count];
sub_process[users[del_user].pid] = del_user;
printf("child %d exit, now we have %d users\n", del_user, user_count);
}
if (terminate && user_count == 0)
{
stop_server = true;
}
break;
}
case SIGTERM:
case SIGINT:
{
printf("kill all the clild now\n");
//addsig( SIGTERM, SIG_IGN );
//addsig( SIGINT, SIG_IGN );
if (user_count == 0)
{
stop_server = true;
break;
}
for (int i = 0; i < user_count; ++i)
{
int pid = users[i].pid;
kill(pid, SIGTERM);
}
terminate = true;
break;
}
default:
{
break;
}
}
}
}
}
else if (events[i].events & EPOLLIN)
{
int child = 0;
ret = recv(sockfd, (char *) &child, sizeof(child), 0);
printf("read data from child accross pipe\n");
if (ret == -1)
{
continue;
}
else if (ret == 0)
{
continue;
}
else
{
for (int j = 0; j < user_count; ++j)
{
if (users[j].pipefd[0] != sockfd)
{
printf("send data to child accross pipe\n");
send(users[j].pipefd[0], (char *) &child, sizeof(child), 0);
}
}
}
}
}
}
del_resource();
return 0;
}