使用“$_exitcode”變量

例子

int main(void)
{
    return 0;
}

技巧

當被調試的程序正常退出時，gdb會使用$_exitcode這個“convenience variable”記錄程序退出時的“exit code”。以調試上面程序為例:

[root@localhost nan]# gdb -q a
Reading symbols from a...done.
(gdb) start
Temporary breakpoint 1 at 0x400478: file a.c, line 3.
Starting program: /home/nan/a

Temporary breakpoint 1, main () at a.c:3
3               return 0;
(gdb) n
4       }
(gdb)
0x00000034e421ed1d in __libc_start_main () from /lib64/libc.so.6
(gdb)
Single stepping until exit from function __libc_start_main,
which has no line number information.
[Inferior 1 (process 1185) exited normally]
(gdb) p $_exitcode
$1 = 0

可以看到打印的$_exitcode的值為0。
改變程序，返回值改為1：

int main(void)
{
    return 0;
}

接著調試：

[root@localhost nan]# gdb -q a
Reading symbols from a...done.
(gdb) start
Temporary breakpoint 1 at 0x400478: file a.c, line 3.
Starting program: /home/nan/a

Temporary breakpoint 1, main () at a.c:3
3               return 1;
(gdb)
(gdb) n
4       }
(gdb)
0x00000034e421ed1d in __libc_start_main () from /lib64/libc.so.6
(gdb)
Single stepping until exit from function __libc_start_main,
which has no line number information.
[Inferior 1 (process 2603) exited with code 01]
(gdb) p $_exitcode
$1 = 1

可以看到打印的$_exitcode的值變為1。
參見gdb手冊.

貢獻者

nanxiao