定位线程Segment fault (SIGSEGV)的方法

使用 valgrind +  memcheck 运行程序, 查找错误的线程id.

   ./valgrind --leak-check=yes --show-reachable=yes ./test   // 这里test为目标程序

==1499== Thread 2:
==1499== Invalid read of size 4
==1499==    at 0x9D70: thread_exec (test.c:152)
==1499==  Address 0x0 is not stack'd, malloc'd or (recently) free'd
==1499== 
==1499== 
==1499== Process terminating with default action of signal 11 (SIGSEGV)
==1499==  Access not within mapped region at address 0x0
==1499==    at 0x9D70: thread_exec (test.c:152)
==1499==  If you believe this happened as a result of a stack
==1499==  overflow in your program's main thread (unlikely but
==1499==  possible), you can try to increase the size of the
==1499==  main thread stack using the --main-stacksize= flag.
==1499==  The main thread stack size used in this run was 8388608.
==1499== 
==1499== HEAP SUMMARY:
==1499==     in use at exit: 272 bytes in 2 blocks
==1499==   total heap usage: 2 allocs, 0 frees, 272 bytes allocated
==1499== 
==1499== Thread 1:
==1499== 272 bytes in 2 blocks are possibly lost in loss record 1 of 1
==1499==    at 0x4832240: calloc (vg_replace_malloc.c:593)
==1499==    by 0x4011203: _dl_allocate_tls (in /lib/ld-2.8.so)
==1499==    by 0x4A4ECA7: pthread_create (in /lib/libpthread-2.8.so)
==1499== 
==1499== LEAK SUMMARY:
==1499==    definitely lost: 0 bytes in 0 blocks
==1499==    indirectly lost: 0 bytes in 0 blocks
==1499==      possibly lost: 272 bytes in 2 blocks
==1499==    still reachable: 0 bytes in 0 blocks

这里显示 线程2出现非法访问, 访问了四个字节. 

注:编译源文件时需要添加 -g 选项. valgrind直接定位出错误的文件和函数位置. 

对于一些引用某些动态库的程序, valgrind可能无法定位出错误的文件和函数位置.

那么我们可以通过一下步骤来获取更多的信息.

1. 为线程设定名字.  以做明确的区分. 

    详见: 为线程设置名字

2.使用valgrind定位出错误的线程id号.

3. 使用valgrind执行程序后, ps 查看程序的id值. 如：ps  | grep test 

4. 进入进程的proc目录. /proc/xxxx/task  

    搜索每个线程的名字.  grep "Name*" */status 如:

1499/status:Name: memcheck-arm-li
1500/status:Name: chk_state
1501/status:Name: chk_pakage

这里可以看出,

该进程的线程1为调试线程.

线程2为线程 chk_state

线程3为线程chk_package

根据步骤2定位出的线程id, 就可以找到出错的具体线程.