Why does GDB hang when using OpenOCD in remote pipe mode?

Question

I'm using GDB and OpenOCD to debug a simple program on my STM32F4DISCOVERY board on Windows. This works fine when starting OpenOCD separately, and using TCP/IP to connect to it, with something like this:

target remote localhost:3333

When I'm done, I can shut down GDB using quit as normal. I would like, however, to use GDB in "remote pipe" mode, instead of needing to start and stop OpenOCD manually. This seems like a somewhat ideal configuration to me. When I do this, however, I cannot exit GDB, as it hangs when I attempt to exit.

The OpenOCD log file shows that the GDB connection was dropped:

Info : dropped 'gdb' connection

But GDB never exits:

(gdb) quit
A debugging session is active.

        Inferior 1 [Remote target] will be detached.

Quit anyway? (y or n) y
Detaching from program: yagarto_sample.elf, Remote target
Ending remote debugging.

The disconnect command similarly hangs, never returing. Not even Ctrl-C will wake up GDB.

Answer 1

It turns out there is a bug in OpenOCD related to a change made by GDB. A bit of detail is here, and a patch has been submitted, and a workaround is provided:

Add this to your cfg:

$_TARGETNAME configure -event gdb-detach { shutdown }

I tested this workaround, and it does work, but in the end, pipe mode is so slow on Windows that I chose to use TCP, even though it is less convenient.