使用“$_exitcode”变量

int main(void)
{
    return 0;
}

技巧

当被调试的程序正常退出时，gdb会使用$_exitcode这个“convenience variable”记录程序退出时的“exit code”。以调试上面程序为例:

[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的值为0。
改变程序，返回值改为1：

int main(void)
{
    return 1;
}

接着调试：

[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的值变为1。
参见 gdb手册.