Attach to process

CLion provides a way to attach the debugger to both local and remote processes.

For C/C++ applications, you can attach to a process with GDB on Windows, LLDB on macOS, and both GDB and LLDB on Linux. When applicable, debuggers for other languages (for example, Python debugger or Swift LLDB) can be used as well.

First off, if you want to debug a program that can be started from CLion, the best way to do it is to start a local debugging session.

Prerequisites for Ubuntu users

If you are using CLion on Ubuntu (or probably, on some other Linux distribution), an error message ptrace: Operation not permitted may appear upon your first attempt to attach to a process. In this case, do one of the following:

To disable this restriction temporarily, enter the command:
echo 0 | sudo tee /proc/sys/kernel/yama/ptrace_scope
To disable this restriction permanently, open the /etc/sysctl.d/10-ptrace.conf file for editing and change the line kernel.yama.ptrace_scope = 1 to kernel.yama.ptrace_scope = 0.
To apply the changes immediately, enter the above command echo 0 | sudo tee /proc/sys/kernel/yama/ptrace_scope.
Alternatively, run sudo service procps restart or restart your system.

You can find more details here.

Attach to a local process

Press Ctrl+Alt+F5 or choose Run | Attach to Process from the main menu.
The list of running local processes is shown. Select the process to attach to.
If necessary, narrow down the list of processes by typing the first letters of its name or PID. If there are several debuggers that can be used for the selected process, you can choose among them in the popup menu:
By default, you will not be able to attach the debugger to a process launched with sudo privileges. As a workaround, try running CLion under the same privileged user.
Proceed with debugging the same way as you usually do it in CLion (set breakpoints, step through, pause and resume the process, evaluate expressions, and so on):
Note that in case the process you have attached to does not provide debug information, breakpoints will be unavailable and stepping will be performed in the disassembly view.

Detach from a process

The procedure to detach from a remote process is the same as for stopping a local debug session, however, the effect is different. When you detach, the debugging session closes but the process continues to run.

Click the Stop button on the main toolbar on in the Debug tool window.
Alternatively, click Stop on the main toolbar or press Ctrl+F2, then select the session to be closed.

Last modified: 12 November 2021