#define _GNU_SOURCE
#include <stdio.h>
#include <stdlib.h>
#include <signal.h>
#include <sched.h>
#include <sys/types.h>
#include <unistd.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <string.h>
#define STACK_SIZE 65536
int a = 0;
int readfd = -1;
int writefd = -1;
int pipe_fd[2];
int test2(void *data)
{
// printf("it is working\n");
int n = 1;
int pos = 0;
int log_fd = 1;
char buf[512];
char log_buf[1024];
memset(buf,'\0',512);
memset(log_buf,'\0',1024);
a = 200;
log_fd = open("./log.txt",O_RDWR|O_CREAT);
if(log_fd < 0)
exit(-1);
sleep(5);
if((n = read(readfd,buf,512) ) <= 0)
{
sprintf(log_buf,"read error\n");
write(log_fd,log_buf,strlen(log_buf));
exit(-1);
}
exit(0);
}
int main(int argc, char *argv[])
{
int fd = -1;
printf("in the main\n");
void *stack=malloc(STACK_SIZE);
a = 100;
if(pipe(pipe_fd) < 0 )
printf("in the main,call the pipe() failed\n");
readfd = pipe_fd[0];
writefd = pipe_fd[1];
printf("In the main,First,current a value:%d\n",a );
int Pid=clone(test2, stack+STACK_SIZE, CLONE_DETACHED|CLONE_FILES, NULL);
printf("In the main,child PID:%d\n",Pid);
if(Pid==-1)
{
printf("clone error\n");
exit(1);
}
if( (fd = open("abc.txt",O_RDWR)) < 0)
printf("in the main,open file ./abc.txt failed\n");
int nbytes = -1;
char send_string[1024];
memset(send_string,'\0',1024);
sprintf(send_string,"the file_fd is:%d",fd);
if((nbytes = write(writefd,send_string,strlen(send_string))) < 0)
printf("in the main,send fd failed\n");
printf("in the main,send %d bytes,the content is----%s\n",nbytes,send_string);
sleep(10);
printf("In the main,Second,current a value:%d\n",a );
printf("yea2");
exit(0);
}
问题：
- 程序可以成功执行，
但是当使用 gdb 跟踪子进程时，我们得到以下错误：
(gdb) b test2 Breakpoint 1 at 0x4007d8: file thread.c, line 25. (gdb) r Starting program: /mnt/hgfs/D/xshell_transmit_folder/thread in the main In the main,First,current a value:100 In the main,child PID:5613 [New LWP 5613] in the main,send 16 bytes,the content is----the file_fd is:9 [Switching to LWP 5613] Breakpoint 1, test2 () at thread.c:25 25 printf("it is working\n"); Missing separate debuginfos, use: debuginfo-install glibc-2.12-1.80.el6.x86_64 (gdb) s 0x0000003d7d067fd0 in puts () from /lib64/libc.so.6 (gdb) s Single stepping until exit from function puts, which has no line number information. Program received signal SIGSEGV, Segmentation fault. 0x0000003d7d0805a1 in __strlen_sse2 () from /lib64/libc.so.6 (gdb)根据错误，子进程出现分段错误，因为子进程访问了一个有效地址。子进程没有正确创建吗？
有人帮我吗？非常感谢你。