为什么每次使用'cont'命令时,在gdb中运行时一个CTRL-Z会不断给出SIGTSTP信号？

Question

我正在开发一个项目Ubuntu Linux,当我使用GDB和中断调试应用程序时CTRL + Z,我得到了SIGTSTP和GDB预期的中断.

但是当我cont在那之后使用时,我仍然有SIGTSTP,我重复cont了很多时间,但接缝它的行为是一样的,只是反复给我SIGTSTP.

以下两个调用堆栈或者重复:

The call stack is as following alterativly:
Program received signal SIGTSTP, Stopped (user).
[Switching to Thread 0x7fffef73d700 (LWP 32591)]
0x00007ffff636dffd in read () from /lib/x86_64-linux-gnu/libc.so.6
(gdb) bt
#0  0x00007ffff636dffd in read () from /lib/x86_64-linux-gnu/libc.so.6
#1  0x00007ffff6301ff8 in _IO_file_underflow () from /lib/x86_64-linux-gnu/libc.so.6
#2  0x00007ffff630303e in _IO_default_uflow () from /lib/x86_64-linux-gnu/libc.so.6
#3  0x00007ffff62f718a in _IO_getline_info () from /lib/x86_64-linux-gnu/libc.so.6
#4  0x00007ffff62f606b in fgets () from /lib/x86_64-linux-gnu/libc.so.6
... .... .... ....
#11 0x00007ffff664ee9a in start_thread () from /lib/x86_64-linux-gnu/libpthread.so.0
#12 0x00007ffff637b3fd in clone () from /lib/x86_64-linux-gnu/libc.so.6
#13 0x0000000000000000 in ?? ()
(gdb) c
Continuing.
Program received signal SIGTSTP, Stopped (user).
[Switching to Thread 0x7fffeef3c700 (LWP 32592)]
0x00007ffff6374763 in select () from /lib/x86_64-linux-gnu/libc.so.6
(gdb) bt
#0  0x00007ffff6374763 in select () from /lib/x86_64-linux-gnu/libc.so.6
... ... ... ...
#6  0x00007ffff664ee9a in start_thread () from /lib/x86_64-linux-gnu/libpthread.so.0
#7  0x00007ffff637b3fd in clone () from /lib/x86_64-linux-gnu/libc.so.6
#8  0x0000000000000000 in ?? ()

那有什么理由吗？谢谢.

Answer 1

gdb 通常(它是可配置的)安排停止程序并在程序即将接收信号时重新获得对终端的控制.

gdb 通常(它是可配置的)在您恢复执行时将信号发送到程序.

可以使用info signals命令查看设置.

(gdb) info signals
Signal        Stop  Print   Pass to program Description
SIGINT        Yes   Yes     No              Interrupt
...
SIGTSTP       Yes   Yes     Yes             Stopped (user)
...

在这种情况下,

• 键入Ctrl-C将停止程序,continue并将恢复它而不向其发送任何信号.
• 键入Ctrl-Z将停止程序,并将continue伴随SIGTSTP信号恢复它,因此它将立即再次停止.如果continue再次输入,则应该恢复.

有两种方法可以在不向其发送SIGTSTP信号的情况下恢复程序.

第一种是使用handle SIGTSTP nopass命令,它将"传递给程序"标志更改为"否".

第二种是使用signal命令代替continue.从内置帮助:

(gdb) help signal
Continue program with the specified signal.
Usage: signal SIGNAL
The SIGNAL argument is processed the same as the handle command.

An argument of "0" means continue the program without sending it a signal.
This is useful in cases where the program stopped because of a signal,
and you want to resume the program while discarding the signal.

因此,signal 0将在没有SIGTSTP信号传递给它的情况下恢复程序.