Linux系统内存产生错误的原因与调试方法

　　core文件终于产生了，用gdb调试一下看看吧:

xiaosuo@gentux test $ gdb ./a.out core
GNU gdb 6.5
Copyright (C) 2006 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 "i686-pc-linux-gnu"...Using host libthread_db library "/lib/libthread_db.so.1".


warning: Can't read pathname for load map: 输入/输出错误.
Reading symbols from /lib/libc.so.6...done.
Loaded symbols for /lib/libc.so.6
Reading symbols from /lib/ld-linux.so.2...done.
Loaded symbols for /lib/ld-linux.so.2
Core was generated by `./a.out'.
Program terminated with signal 11, Segmentation fault.
#0 0x08048524 in dummy_function () at d.c:4
4 *ptr = 0x00;

　　还是一步就定位到了错误所在地，佩服一下Linux/Unix系统的此类设计。
接着考虑下去，以前用windows系统下的ie的时侯，有时打开某些网页，会出现“运行时错误”，这个时侯如果恰好你的机器上又装有windows的编译器的话，他会弹出来一个对话框，问你是否进行调试，如果你选择是，编译器将被打开，并进入调试状态，开始调试。

　　Linux下如何做到这些呢？我的大脑飞速地旋转着，有了，让它在SIGSEGV的handler中调用gdb，于是第三个方法又诞生了：

　　3.段错误时启动调试:

#include
#include
#include
#include

void dump(int signo)
{
char buf[1024];
char cmd[1024];
FILE *fh;

snprintf(buf, sizeof(buf), "/proc/%d/cmdline", getpid());
if(!(fh = fopen(buf, "r")))
exit(0);
if(!fgets(buf, sizeof(buf), fh))
exit(0);
fclose(fh);
if(buf[strlen(buf) - 1] == 'n')
buf[strlen(buf) - 1] = '';
snprintf(cmd, sizeof(cmd), "gdb %s %d", buf, getpid());
system(cmd);

exit(0);
}

void
dummy_function (void)
{
unsigned char *ptr = 0x00;
*ptr = 0x00;
}

int
main (void)
{
signal(SIGSEGV, &dump);
dummy_function ();

return 0;
}


　　编译运行效果如下：

xiaosuo@gentux test $ gcc -g -rdynamic f.c
xiaosuo@gentux test $ ./a.out
GNU gdb 6.5
Copyright (C) 2006 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 "i686-pc-linux-gnu"...Using host libthread_db library "/lib/libthread_db.so.1".

Attaching to program: /home/xiaosuo/test/a.out, process 9563
Reading symbols from /lib/libc.so.6...done.
Loaded symbols for /lib/libc.so.6
Reading symbols from /lib/ld-linux.so.2...done.
Loaded symbols for /lib/ld-linux.so.2
0xffffe410 in __kernel_vsyscall ()
(gdb) bt
#0 0xffffe410 in __kernel_vsyscall ()
#1 0xb7ee4b53 in waitpid () from /lib/libc.so.6
#2 0xb7e925c9 in strtold_l () from /lib/libc.so.6
#3 0x08048830 in dump (signo=11) at f.c:22
#4
#5 0x0804884c in dummy_function () at f.c:31
#6 0x08048886 in main () at f.c:38