具有 FIFO 管道的分段错误（核心转储）以及服务器和客户端之间的分叉通信
Segmentation fault (core dumped) with FIFO pipes and fork communication between server and client
我正在编写一个项目，您可以在一个终端中启动服务器，而在作为客户端的其他终端中，您可以使用 FIFO 管道将消息从一个用户发送到另一个用户。服务器创建从客户端读取消息的 FIFO 管道。客户端创建 FIFO 管道以从服务器读取消息。
在一个启动服务器的终端中，我键入 ./projectname --start，在客户端中，我键入 ./projectname --login nickname。当我关闭客户端时，我的服务器收到分段错误（核心转储）错误消息。在 x 小时内，我试图以我所知道的一切可能的方式摆脱它。如何修复？
我也曾尝试使用 void verifyloginclient(char *login) 函数注册用户，但父进程无法从子进程接收信息并陷入无限状态 while(1) 向服务器发送一些消息，这也使服务器因分段错误而崩溃，因此它被评论现在。
#include <stdio.h>
#include <stdlib.h>
#include <getopt.h>
#include <sys/types.h>
#include <sys/wait.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <unistd.h>
#include <string.h>
#include <signal.h>
char userlist[10][30];
int succesfulllogin = 1;
void handler(int signum){
pid_t pid;
pid = wait(NULL);
succesfulllogin = 0;
printf("Parent knows child %d finished\n", (int)pid);
printf("Parent ending...\n");
}
void sig_handler_parent(int signum){
printf("signal response from child!\n");
succesfulllogin = 0;
exit(0);
}
void sig_handler_child(int signum){
printf("signal from parent\n");
succesfulllogin = 0;
exit(0);
}
void verifyloginclient(char *login)
{
int fd;
char buf[256];
char buf2[256];
snprintf(buf, sizeof buf, "%s%s", "fifopipes/","serwer.fifo");
if((fd = open(buf, O_WRONLY)) == -1){
perror("openFdloginclient");
exit(EXIT_FAILURE);
}
snprintf(buf2, sizeof buf2, "%s%s%s", login, " /login ",login);
if((write(fd, buf2, strlen(buf2))) == -1){
perror("writeloginclient");
}
close(fd);
}
int verifyloginserwer(char *login)
{
// check if login is on the userlist
int flagcmp = -1;
int x;
int indeks=0;
for(int i=0;i<10;i++){
x = strcmp(&userlist[i][0],login);
if(x==0){
flagcmp = i;
}
}
if(flagcmp == -1){ //if it doesnt exist we add him to first free slot
for(int i=0;i<10;i++){
if(userlist[i][0]=='[=10=]'){
strcpy(userlist[i],login);
printf("userlist: %s\n", userlist[i]);
succesfulllogin = 1;
break;
}
else{
indeks++;
}
}
}
else if(flagcmp != -1 || indeks==10){
fprintf(stderr, "loggin error!\n");
succesfulllogin = 0;
return 2;
}
return 0;
}
int splitstring(char *source, int desiredlength, char **s1,char **s2)
{
int len;
len = strlen(source);
if (desiredlength > len)
return(0);
*s1 = (char *) malloc(sizeof(char) * desiredlength);
*s2 = (char *) malloc(sizeof(char) * len-desiredlength+1);
if(s1 ==NULL || s2 == NULL)
return 0;
strncpy(*s1,source,desiredlength);
strncpy(*s2,source+desiredlength, len-desiredlength);
return(1);
}
void startserwer()
{
int fdserwer;
int fdanuluj;
int fd;
char readbuf[80];
int read_bytes;
char buf[256]; //pipe server
char buf2[256]; //pipe client
char buf3[256]; // message to client
for(int i=0;i<10;i++){ // declare userlist
userlist[i][0] = '[=10=]';
}
snprintf(buf, sizeof buf, "%s%s", "fifopipes/","serwer.fifo");
umask(0);
if(mkfifo(buf, 0777) == -1){
perror("mkfifoserwer");
exit(EXIT_FAILURE);
}
while(1){
if((fdserwer = open(buf, O_CREAT | O_RDONLY))== -1){
perror("openFdserwer");
exit(EXIT_FAILURE);
}
if((read_bytes = read(fdserwer, &readbuf, sizeof(readbuf)))== -1){
perror("readbytes");
}
else{
readbuf[read_bytes] = '[=10=]';
//SENDER LOGIN
char senderlogin[80];
strcpy(senderlogin, readbuf);
char *token = strtok(senderlogin, " ");
printf("%s\n", token);
strcpy(senderlogin, token);
int b;
char *loginnadawcy;
char *resztakomendy;
b = splitstring(readbuf, (int) strlen(token)+1,&loginnadawcy,&resztakomendy);
if(b!=1){
printf("error in command\n");
}
else{
loginnadawcy[strlen(token)]='[=10=]';
//COMMAND NAME AFTER SLASH /
char command[80];
strcpy(command, readbuf);
token = strtok(NULL, " ");
printf("%s\n",token);
strcpy(command, token);
int a;
char *komenda;
char *reszta;
a = splitstring(resztakomendy, (int)strlen(token)+1,&komenda,&reszta);
if(a!=1){
printf("error\n");
}
else{
komenda[strlen(token)]='[=10=]';
if(strcmp(komenda,"/login")==0){
if(verifyloginserwer(senderlogin)==2){
//open client pipe
snprintf(buf2, sizeof buf2, "%s%s%s", "fifopipes/",senderlogin,".fifo");
if((fdanuluj = open(buf2, O_WRONLY)) == -1){
perror("openFdanuluj");
exit(EXIT_FAILURE);
}
//SEND MESSAGE TO CLIENT
snprintf(buf3, sizeof buf3, "%s%s", "serwer ", "end");
if((write(fdanuluj, buf3, strlen(buf3))) == -1){
perror("writeFdanuluj");
}
close(fdanuluj);
}
}
else if(strcmp(komenda,"/w")==0){
//RECEIVER LOGIN
char receiverlogin[80];
token = strtok(NULL, " ");
printf("%s\n",token);
strcpy(receiverlogin, token);
int r;
char *login;
char *message;
r = splitstring(reszta,(int)strlen(token)+1,&login,&message);
if(r!=1){
printf("error\n");
}
else{
//RECEIVE INFORMATION
login[strlen(receiverlogin)]='[=10=]';
printf("from %s to %s: %s and length is %d \n", senderlogin, login, message, (int)strlen(message));
//OPEN CLIENT PIPE
snprintf(buf2, sizeof buf2, "%s%s%s", "fifopipes/",receiverlogin,".fifo");
if((fd = open(buf2, O_WRONLY))== -1){
perror("openFd");
exit(EXIT_FAILURE);
}
//SEND MESSAGE TO CLIENT
snprintf(buf3, sizeof buf3, "%s%s%s", senderlogin," ",message);
if( (write(fd, buf3, strlen(buf3) )) == -1){
perror("writeopenfd");
}
close(fd);
}
}
}
}
}
close(fdserwer);
}
unlink(buf);
}
void clientchild(char *login)
{
int fd;
char readbuf[80];
int read_bytes;
char buf[256];
snprintf(buf, sizeof buf, "%s%s%s", "fifopipes/",login,".fifo");
umask(0);
if(mkfifo(buf, 0777) == -1){
perror("mkfifoclient");
exit(EXIT_FAILURE);
}
while(1){
if((fd = open(buf, O_CREAT | O_RDONLY)) == -1){
perror("openFdchild");
exit(EXIT_FAILURE);
}
if((read_bytes = read(fd, &readbuf, sizeof(readbuf))) == -1){
perror("readfdchild");
}
else{
readbuf[read_bytes] = '[=10=]';
//SENDER LOGIN
char nickname[80];
strcpy(nickname, readbuf);
char * token = strtok(nickname, " ");
//printf("%s\n",token);
int r;
char *login;
char *message;
r = splitstring(readbuf,(int)strlen(token)+1,&login,&message);
if(r!=1){
printf("blad\n");
}
else{
login[strlen(token)]='[=10=]';
if(strcmp(login,"serwer")==0 && strcmp(message,"end")==0){
printf("Login error. Closing...\n");
close(fd);
break;
}
printf("%s: %s and length is %d \n", login, message, (int)strlen(message));
close(fd);
//printf("Received string: \"%s\" and length is %d \n", readbuf, (int)strlen(readbuf));
}
//free(login);
//free(message);
}
}
unlink(buf);
}
void clientparent(char *login)
{
signal(SIGQUIT,sig_handler_parent);
int fd;
int stringlen;
char readbuf[80];
char buf[256];
char buf2[256];
snprintf(buf, sizeof buf, "%s%s", "fifopipes/","serwer.fifo");
printf("FIFO_CLIENT: Send messages infinitely\n");
while(1){
if((fd = open(buf, O_WRONLY)) == -1){
perror("openFdparent");
exit(EXIT_FAILURE);
}
//printf("Enter string: ");
fgets(readbuf, sizeof(readbuf), stdin);
stringlen = strlen(readbuf);
readbuf[stringlen - 1] = '[=10=]';
snprintf(buf2, sizeof buf2, "%s%s%s", login," ",readbuf);
if(strlen(login)+1 == strlen(buf2)){
printf("Error\n");
break;
}
else{
if((write(fd, buf2, strlen(buf2))) == -1){
perror("writeparent");
}
printf("Sent string: \"%s\" and string length is %d \n", buf2, (int)strlen(buf2));
}
}
close(fd);
}
void splitclient(char *login)
{
printf("login: %s\n", login);
pid_t pid = fork();
printf("fork returned: %d\n", (int) pid);
//signal(SIGCHLD, handler);
if (pid < 0){
perror("Fork failed");
}
else if (pid == 0){
signal(SIGQUIT,sig_handler_child);
printf("I am the child with pid %d\n", (int) getpid());
char buf[256];
snprintf(buf, sizeof buf, "%s%d", "Child ",(int) getpid());
//kod dziecka
clientchild(login);
//kill(getppid(),SIGQUIT);
exit(0);
}
else{
// We must be the parent
printf("I am the parent, waiting for child to end \n");
//kod rodzica
clientparent(login);
pid_t childpid = wait(NULL);
printf("Parent knows child %d finished\n", (int)childpid);
printf("Parent ending...\n");
}
}
int main(int argc, char **argv)
{
while(1)
{
int c;
int option_index = 0;
static struct option long_options[] =
{
{"start", no_argument, NULL, 's'},
{"login", required_argument, NULL, 'l'},
{0, 0, 0, 0}
};
c = getopt_long (argc, argv, "sl:", long_options, &option_index);
if (c == -1)
break;
switch (c)
{
case 's':
printf("start server\n");
startserwer();
break;
case 'l':
printf("login with option %s \n", optarg);
//verifyloginclient(optarg);
splitclient(optarg);
break;
case '?':
break;
default:
abort();
}
}
if (optind < argc)
{
printf("non-option ARGV-elements: ");
while (optind < argc)
printf("%s ", argv[optind++]);
putchar ('\n');
}
return 0;
}
来自startServer()中的代码：
if((read_bytes = read(fdserwer, &readbuf, sizeof(readbuf)))== -1){
perror("readbytes");
}
else{
:
char *token = strtok(senderlogin, " ");
:
strcpy(senderlogin, token);
b = splitstring(readbuf, (int)
strlen(token)+1,&loginnadawcy,&resztakomendy);
您没有验证 token 是否是非 NULL 指针 post 标记化。在 child 退出的情况下，read() 将 return 为 0（而不是 -1 作为失败），表明 EOF 正如 man 告诉的那样：
RETURN VALUE
On success, the number of bytes read is returned (zero indicates
end of file),
因此 senderlogin 缓冲区将是空的并且不会产生任何标记。您需要考虑这种情况并进行适当的空值检查。添加空 chek 将导致服务器程序正常退出。
我正在编写一个项目，您可以在一个终端中启动服务器，而在作为客户端的其他终端中，您可以使用 FIFO 管道将消息从一个用户发送到另一个用户。服务器创建从客户端读取消息的 FIFO 管道。客户端创建 FIFO 管道以从服务器读取消息。
在一个启动服务器的终端中，我键入 ./projectname --start，在客户端中，我键入 ./projectname --login nickname。当我关闭客户端时，我的服务器收到分段错误（核心转储）错误消息。在 x 小时内，我试图以我所知道的一切可能的方式摆脱它。如何修复？
我也曾尝试使用 void verifyloginclient(char *login) 函数注册用户，但父进程无法从子进程接收信息并陷入无限状态 while(1) 向服务器发送一些消息，这也使服务器因分段错误而崩溃，因此它被评论现在。
#include <stdio.h>
#include <stdlib.h>
#include <getopt.h>
#include <sys/types.h>
#include <sys/wait.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <unistd.h>
#include <string.h>
#include <signal.h>
char userlist[10][30];
int succesfulllogin = 1;
void handler(int signum){
pid_t pid;
pid = wait(NULL);
succesfulllogin = 0;
printf("Parent knows child %d finished\n", (int)pid);
printf("Parent ending...\n");
}
void sig_handler_parent(int signum){
printf("signal response from child!\n");
succesfulllogin = 0;
exit(0);
}
void sig_handler_child(int signum){
printf("signal from parent\n");
succesfulllogin = 0;
exit(0);
}
void verifyloginclient(char *login)
{
int fd;
char buf[256];
char buf2[256];
snprintf(buf, sizeof buf, "%s%s", "fifopipes/","serwer.fifo");
if((fd = open(buf, O_WRONLY)) == -1){
perror("openFdloginclient");
exit(EXIT_FAILURE);
}
snprintf(buf2, sizeof buf2, "%s%s%s", login, " /login ",login);
if((write(fd, buf2, strlen(buf2))) == -1){
perror("writeloginclient");
}
close(fd);
}
int verifyloginserwer(char *login)
{
// check if login is on the userlist
int flagcmp = -1;
int x;
int indeks=0;
for(int i=0;i<10;i++){
x = strcmp(&userlist[i][0],login);
if(x==0){
flagcmp = i;
}
}
if(flagcmp == -1){ //if it doesnt exist we add him to first free slot
for(int i=0;i<10;i++){
if(userlist[i][0]=='[=10=]'){
strcpy(userlist[i],login);
printf("userlist: %s\n", userlist[i]);
succesfulllogin = 1;
break;
}
else{
indeks++;
}
}
}
else if(flagcmp != -1 || indeks==10){
fprintf(stderr, "loggin error!\n");
succesfulllogin = 0;
return 2;
}
return 0;
}
int splitstring(char *source, int desiredlength, char **s1,char **s2)
{
int len;
len = strlen(source);
if (desiredlength > len)
return(0);
*s1 = (char *) malloc(sizeof(char) * desiredlength);
*s2 = (char *) malloc(sizeof(char) * len-desiredlength+1);
if(s1 ==NULL || s2 == NULL)
return 0;
strncpy(*s1,source,desiredlength);
strncpy(*s2,source+desiredlength, len-desiredlength);
return(1);
}
void startserwer()
{
int fdserwer;
int fdanuluj;
int fd;
char readbuf[80];
int read_bytes;
char buf[256]; //pipe server
char buf2[256]; //pipe client
char buf3[256]; // message to client
for(int i=0;i<10;i++){ // declare userlist
userlist[i][0] = '[=10=]';
}
snprintf(buf, sizeof buf, "%s%s", "fifopipes/","serwer.fifo");
umask(0);
if(mkfifo(buf, 0777) == -1){
perror("mkfifoserwer");
exit(EXIT_FAILURE);
}
while(1){
if((fdserwer = open(buf, O_CREAT | O_RDONLY))== -1){
perror("openFdserwer");
exit(EXIT_FAILURE);
}
if((read_bytes = read(fdserwer, &readbuf, sizeof(readbuf)))== -1){
perror("readbytes");
}
else{
readbuf[read_bytes] = '[=10=]';
//SENDER LOGIN
char senderlogin[80];
strcpy(senderlogin, readbuf);
char *token = strtok(senderlogin, " ");
printf("%s\n", token);
strcpy(senderlogin, token);
int b;
char *loginnadawcy;
char *resztakomendy;
b = splitstring(readbuf, (int) strlen(token)+1,&loginnadawcy,&resztakomendy);
if(b!=1){
printf("error in command\n");
}
else{
loginnadawcy[strlen(token)]='[=10=]';
//COMMAND NAME AFTER SLASH /
char command[80];
strcpy(command, readbuf);
token = strtok(NULL, " ");
printf("%s\n",token);
strcpy(command, token);
int a;
char *komenda;
char *reszta;
a = splitstring(resztakomendy, (int)strlen(token)+1,&komenda,&reszta);
if(a!=1){
printf("error\n");
}
else{
komenda[strlen(token)]='[=10=]';
if(strcmp(komenda,"/login")==0){
if(verifyloginserwer(senderlogin)==2){
//open client pipe
snprintf(buf2, sizeof buf2, "%s%s%s", "fifopipes/",senderlogin,".fifo");
if((fdanuluj = open(buf2, O_WRONLY)) == -1){
perror("openFdanuluj");
exit(EXIT_FAILURE);
}
//SEND MESSAGE TO CLIENT
snprintf(buf3, sizeof buf3, "%s%s", "serwer ", "end");
if((write(fdanuluj, buf3, strlen(buf3))) == -1){
perror("writeFdanuluj");
}
close(fdanuluj);
}
}
else if(strcmp(komenda,"/w")==0){
//RECEIVER LOGIN
char receiverlogin[80];
token = strtok(NULL, " ");
printf("%s\n",token);
strcpy(receiverlogin, token);
int r;
char *login;
char *message;
r = splitstring(reszta,(int)strlen(token)+1,&login,&message);
if(r!=1){
printf("error\n");
}
else{
//RECEIVE INFORMATION
login[strlen(receiverlogin)]='[=10=]';
printf("from %s to %s: %s and length is %d \n", senderlogin, login, message, (int)strlen(message));
//OPEN CLIENT PIPE
snprintf(buf2, sizeof buf2, "%s%s%s", "fifopipes/",receiverlogin,".fifo");
if((fd = open(buf2, O_WRONLY))== -1){
perror("openFd");
exit(EXIT_FAILURE);
}
//SEND MESSAGE TO CLIENT
snprintf(buf3, sizeof buf3, "%s%s%s", senderlogin," ",message);
if( (write(fd, buf3, strlen(buf3) )) == -1){
perror("writeopenfd");
}
close(fd);
}
}
}
}
}
close(fdserwer);
}
unlink(buf);
}
void clientchild(char *login)
{
int fd;
char readbuf[80];
int read_bytes;
char buf[256];
snprintf(buf, sizeof buf, "%s%s%s", "fifopipes/",login,".fifo");
umask(0);
if(mkfifo(buf, 0777) == -1){
perror("mkfifoclient");
exit(EXIT_FAILURE);
}
while(1){
if((fd = open(buf, O_CREAT | O_RDONLY)) == -1){
perror("openFdchild");
exit(EXIT_FAILURE);
}
if((read_bytes = read(fd, &readbuf, sizeof(readbuf))) == -1){
perror("readfdchild");
}
else{
readbuf[read_bytes] = '[=10=]';
//SENDER LOGIN
char nickname[80];
strcpy(nickname, readbuf);
char * token = strtok(nickname, " ");
//printf("%s\n",token);
int r;
char *login;
char *message;
r = splitstring(readbuf,(int)strlen(token)+1,&login,&message);
if(r!=1){
printf("blad\n");
}
else{
login[strlen(token)]='[=10=]';
if(strcmp(login,"serwer")==0 && strcmp(message,"end")==0){
printf("Login error. Closing...\n");
close(fd);
break;
}
printf("%s: %s and length is %d \n", login, message, (int)strlen(message));
close(fd);
//printf("Received string: \"%s\" and length is %d \n", readbuf, (int)strlen(readbuf));
}
//free(login);
//free(message);
}
}
unlink(buf);
}
void clientparent(char *login)
{
signal(SIGQUIT,sig_handler_parent);
int fd;
int stringlen;
char readbuf[80];
char buf[256];
char buf2[256];
snprintf(buf, sizeof buf, "%s%s", "fifopipes/","serwer.fifo");
printf("FIFO_CLIENT: Send messages infinitely\n");
while(1){
if((fd = open(buf, O_WRONLY)) == -1){
perror("openFdparent");
exit(EXIT_FAILURE);
}
//printf("Enter string: ");
fgets(readbuf, sizeof(readbuf), stdin);
stringlen = strlen(readbuf);
readbuf[stringlen - 1] = '[=10=]';
snprintf(buf2, sizeof buf2, "%s%s%s", login," ",readbuf);
if(strlen(login)+1 == strlen(buf2)){
printf("Error\n");
break;
}
else{
if((write(fd, buf2, strlen(buf2))) == -1){
perror("writeparent");
}
printf("Sent string: \"%s\" and string length is %d \n", buf2, (int)strlen(buf2));
}
}
close(fd);
}
void splitclient(char *login)
{
printf("login: %s\n", login);
pid_t pid = fork();
printf("fork returned: %d\n", (int) pid);
//signal(SIGCHLD, handler);
if (pid < 0){
perror("Fork failed");
}
else if (pid == 0){
signal(SIGQUIT,sig_handler_child);
printf("I am the child with pid %d\n", (int) getpid());
char buf[256];
snprintf(buf, sizeof buf, "%s%d", "Child ",(int) getpid());
//kod dziecka
clientchild(login);
//kill(getppid(),SIGQUIT);
exit(0);
}
else{
// We must be the parent
printf("I am the parent, waiting for child to end \n");
//kod rodzica
clientparent(login);
pid_t childpid = wait(NULL);
printf("Parent knows child %d finished\n", (int)childpid);
printf("Parent ending...\n");
}
}
int main(int argc, char **argv)
{
while(1)
{
int c;
int option_index = 0;
static struct option long_options[] =
{
{"start", no_argument, NULL, 's'},
{"login", required_argument, NULL, 'l'},
{0, 0, 0, 0}
};
c = getopt_long (argc, argv, "sl:", long_options, &option_index);
if (c == -1)
break;
switch (c)
{
case 's':
printf("start server\n");
startserwer();
break;
case 'l':
printf("login with option %s \n", optarg);
//verifyloginclient(optarg);
splitclient(optarg);
break;
case '?':
break;
default:
abort();
}
}
if (optind < argc)
{
printf("non-option ARGV-elements: ");
while (optind < argc)
printf("%s ", argv[optind++]);
putchar ('\n');
}
return 0;
}
来自startServer()中的代码：
if((read_bytes = read(fdserwer, &readbuf, sizeof(readbuf)))== -1){
perror("readbytes");
}
else{
:
char *token = strtok(senderlogin, " ");
:
strcpy(senderlogin, token);
b = splitstring(readbuf, (int)
strlen(token)+1,&loginnadawcy,&resztakomendy);
您没有验证 token 是否是非 NULL 指针 post 标记化。在 child 退出的情况下，read() 将 return 为 0（而不是 -1 作为失败），表明 EOF 正如 man 告诉的那样：
RETURN VALUE
On success, the number of bytes read is returned (zero indicates end of file),
因此 senderlogin 缓冲区将是空的并且不会产生任何标记。您需要考虑这种情况并进行适当的空值检查。添加空 chek 将导致服务器程序正常退出。