[cdt-dev] 'continue' executed via gdb.post_event() breaks run control in

[Adrian Oltean <adrian.oltean@xxxxxxx>]

Hi everyone,

 

I’m currently experiencing some problems with regards to how CDT behaves

in the use case described in detail below. Looks like a 'continue' executed

via GDB's python API (see gdb.post_event(event)) somehow confuses Eclipse.

 

How to easily reproduce the problem:

1. Use an Ubuntu/Windows host;

2. Install Eclipse C/C++ 2019.12;

3. Create a C 'hello world' app for testing; add an infinite loop in 'main';

4. Build the app;

5. Create a python script (e.g. post_event.py) and paste the following code.

Make sure to properly indent it if it gets messed-up in this email;

import gdb

 

class CustomEvent(object):

    def __init__(self, command):

        self.command = command

 

    def __call__(self):

        print("Executing <%s>" % self.command)

        gdb.execute(self.command, False, False)

 

counter = 0

def suspend_handler(event):

    global counter

    if counter % 2 == 0:

        gdb.post_event(CustomEvent("continue"))

    counter = counter + 1

 

# This is not part of the suspend_handler...

gdb.events.stop.connect(suspend_handler)

 

6. Start local debug; use GDB 8+ in all-stop mode;

7. Run the py script using the Debugger Console - 'source post_event.py';

8. Resume the app from 'main'

9. Suspend execution - note that a 'continue' will (eventually) be executed

from the script. We have two behaviors, depending on the host OS:

  a. On Linux ('enhanced' console supported), Eclipse ends-up in a weird

state, Debug view showing the app suspended (with empty stack frames) whilst

the actual app is running. Suspend button is now disabled. If I try to resume,

I obviously get an error - 'selected thread is running';

  b. On Windows (no 'enhanced' debugger console support, thus no mi-async,

nor target-sync enabled), suspend operation fails with 'operation timeout'. Things

get really messy if trying other operations afterwards.

10. Repeat steps 8 and 9 if problem not reproduced after the first attempt. Seems

to be more reliable on Linux hosts but consistently failing on Windows;

 

I'm mentioning the 'enhanced' console support because problems seem to be related

to how app/target is interrupted - '-exec-interrupt' vs. kill(SIGINT).

 

From my experiments, if I switch to non-stop mode GDB, behavior on Linux does not

change, whereas on Windows I no longer see any issues. But on Windows, my setup

involves an ARM-based target, a custom GDB server and JTAG debugging. On my

Ubuntu 18.04 I simply debug a host Linux app.

 

Anyone else seeing this? Any hints on how to make CDT properly deal with

'continue' executed from a gdb.post_event()?

 

Thank you,

Adrian