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Howto debug C-code with forks [message #1709010]

Wed, 23 September 2015 09:50

star bright

Messages: 17
Registered: September 2015

Junior Member

I get the debugging work with gdbserver at the device (cross compiled). The issue is, how to follow a fork?
Different threads I can observe in the debug window, but how about forks?

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Re: Howto debug C-code with forks [message #1709038 is a reply to message #1709010]

Wed, 23 September 2015 13:15

Marc Khouzam

Messages: 357
Registered: July 2009

Senior Member

Run->Debug Configurations...
then select the launch you use.
Go to the Debugger subtab and at the bottom select "Automatically debug forked processes" You need GDB 7.2 or higher to do this.

Marc

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Re: Howto debug C-code with forks [message #1709118 is a reply to message #1709038]

Thu, 24 September 2015 08:07

star bright

Messages: 17
Registered: September 2015

Junior Member

Thanks Marc. Indeed I have a 7.8.1 version. This seems to be a very global setting, so no change during runtime?T
his selection is not available in this debugger-subtab in Luna, but only in Mars.
Unfortunatly I currently stick on Luna for Yocto. Maybe next Yocto release supports Mars.
Anyhow, thanks for this information. Did you ever used that - if so how is your experience?

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Re: Howto debug C-code with forks [message #1709146 is a reply to message #1709118]

Thu, 24 September 2015 13:09

Marc Khouzam

Messages: 357
Registered: July 2009

Senior Member

Debugging forked processes, and it's option in the Debugger subtab (not the main subtab) has been there much before luna:
https://wiki.eclipse.org/CDT/User/NewIn80#Multi-process_Debugging

If for some reason you still cannot find this option, you can add the following command to your .gdbinit file:
set detach-on-fork off
and I believe it will have the exact same effect.

Marc

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Re: Howto debug C-code with forks [message #1709265 is a reply to message #1709146]

Fri, 25 September 2015 12:35

star bright

Messages: 17
Registered: September 2015

Junior Member

Mh, not sure I get it. Wiki talks about "only Non-Stop debugging sessions".
Is this without activating in Debug Config/Debugger/Stop on startup?
I didn't had a .gdbinit, so I created one with "set detach-on-fork off".
But both changes doesn't make a difference. The icon in the WIKI (that looks like a rotated Z) is greyed out here.

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Re: Howto debug C-code with forks [message #1709286 is a reply to message #1709265]

Fri, 25 September 2015 15:43

Marc Khouzam

Messages: 357
Registered: July 2009

Senior Member

Ah yes, to get multi-process debugging you need to enable non-stop debugging.
CDT does not support multi-process with all-stop.

Another way to do this is to stick to single-process debug but follow the child instead of the parent.
To do that, in your .gdbinit file use the command
set follow-fork-mode child

Marc

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