转 GDB 调试 core文件

在Linux下产生并调试core文件

2009-03-10 14:32

$ uname -a Linux dev 2.4.21-9.30AXsmp #1 SMP Wed May 26 23:37:09 EDT 2004 i686 i686 i386 GNU/Linux 再看看默认的一些参数，注意core file size是个0，程序出错时不会产生core文件了。 $ ulimit -a core file size (blocks, -c) 0 data seg size (kbytes, -d) unlimited file size (blocks, -f) unlimited max locked memory (kbytes, -l) 4 max memory size (kbytes, -m) unlimited open files (-n) 2048 pipe size (512 bytes, -p) 8 stack size (kbytes, -s) 10240 cpu time (seconds, -t) unlimited max user processes (-u) 7168 virtual memory (kbytes, -v) unlimited 写个简单的程序，看看core文件是不是会被产生。 $ more foo.c #include <stdio.h> static void sub(void); int main(void) {      sub();      return 0; } static void sub(void) {      int *p = NULL;      /* derefernce a null pointer, expect core dump. */      printf("%d", *p); } $ gcc -Wall -g foo.c $ ./a.out Segmentation fault $ ls -l core.* ls: core.*: No such file or directory 没有找到core文件，我们改改ulimit的设置，让它产生。1024是随便取的，要是core文件大于1024个块，就产生不出来了。 $ ulimit -c 1024 $ ulimit -a core file size (blocks, -c) 1024 data seg size (kbytes, -d) unlimited file size (blocks, -f) unlimited max locked memory (kbytes, -l) 4 max memory size (kbytes, -m) unlimited open files (-n) 2048 pipe size (512 bytes, -p) 8 stack size (kbytes, -s) 10240 cpu time (seconds, -t) unlimited max user processes (-u) 7168 virtual memory (kbytes, -v) unlimited $ ./a.out Segmentation fault (core dumped) $ ls -l core.* -rw------- 1 uniware uniware 53248 Jun 30 17:10 core.9128 注意看上述的输出信息，多了个(core dumped)。确实产生了一个core文件，9128是该进程的PID。我们用GDB来看看这个core。 $ gdb --core=core.9128 GNU gdb Asianux (6.0post-0.20040223.17.1AX) Copyright 2004 Free Software Foundation, Inc. GDB is free software, covered by the GNU General Public License, and you are welcome to change it and/or distribute copies of it under certain conditions. Type "show copying" to see the conditions. There is absolutely no warranty for GDB. Type "show warranty" for details. This GDB was configured as "i386-asianux-linux-gnu". Core was generated by `./a.out'. Program terminated with signal 11, Segmentation fault. #0 0x08048373 in ?? () (gdb) bt #0 0x08048373 in ?? () #1 0xbfffd8f8 in ?? () #2 0x0804839e in ?? () #3 0xb74cc6b3 in ?? () #4 0x00000000 in ?? () 此时用bt看不到backtrace，也就是调用堆栈，原来GDB还不知道符号信息在哪里。我们告诉它一下： (gdb) file ./a.out Reading symbols from ./a.out...done. Using host libthread_db library "/lib/tls/libthread_db.so.1". (gdb) bt #0 0x08048373 in sub () at foo.c:17 #1 0x08048359 in main () at foo.c:8 此时backtrace出来了。 (gdb) l 8         sub(); 9         return 0; 10     } 11 12      static void sub(void) 13      { 14          int *p = NULL; 15 16          /* derefernce a null pointer, expect core dump. */ 17          printf("%d", *p); (gdb)