Linux下多執行緒程式發生coredump時，用

gdb /path/to/program/file core

可以看到所有執行緒

[email protected]:~/test/thread# gdb a.out core
GNU gdb (GDB) 7.6.1
Copyright (C) 2013 Free Software Foundation, Inc.
License GPLv3+: GNU GPL version 3 or later <http://gnu.org/licenses/gpl.html>
This is free software: you are free to change and redistribute it.
There is NO WARRANTY, to the extent permitted by law.  Type "show copying"
and "show warranty" for details.
This GDB was configured as "i486-slackware-linux".
For bug reporting instructions, please see:
<http://www.gnu.org/software/gdb/bugs/>...
Reading symbols from /root/test/thread/a.out...done.
[New LWP 826]
[New LWP 825]

但是哪個執行緒才是導致coredump的執行緒呢？

一般用gettid()函式就可以得到，但gittid在預設配置下會連結失敗

這時就要靠系統呼叫出馬了

#include <stdio.h>
#include <sys/syscall.h>//Linux system call for thread id
#include <assert.h>
#include <pthread.h>

void *nbi(void *arg)
{
        int i;
        printf("child thread lwpid = %u\n", syscall(SYS_gettid));
        printf("child thread tid = %u\n", pthread_self());
        scanf("%d", i);//code dump
}
int main()
{
        pthread_t tid;
        int rc;
        printf("main thread lwpid = %u\n", syscall(SYS_gettid));
        printf("main thread tid = %u\n", pthread_self());
        rc = pthread_create(&tid, NULL, nbi, NULL);
        assert(0 == rc);
        pthread_join(tid, NULL);

        return 0;
}
 

[email protected]:~/test/thread# ./a.out
main thread lwpid = 825
main thread tid = 3076090112
child thread lwpid = 826
child thread tid = 3076086592
12
Segmentation fault (core dumped)

coredump原因：

(gdb) bt
#0  0xb75ed50e in __GI__IO_vfscanf () from /lib/libc.so.6
#1  0xb75fc183 in __isoc99_scanf () from /lib/libc.so.6
#2  0x080486ca in nbi (arg=0x0) at test.c:12
#3  0xb7728955 in start_thread () from /lib/libpthread.so.0
#4  0xb767e1ae in clone () from /lib/libc.so.6
(gdb) 

向0x0000000c（保留地址）寫資料導致sigsegv