A little OT. Debug a ncurses C program with eclipse

Paulo da Silva

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Jul 19, 2021, 3:15:55 PM7/19/21

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Hi!

I have tried lots of ideas from Google search but still didn't get any
success debugging a C program with ncurses using eclipse! I think that's
mainly because the suggestions are for older eclipse versions.

This should be simple. It's only a matter of being able to insert
-tty=/dev/pts/X in the gdb command line issued by eclipse, I think. X is
obtained by tty command on a pretended terminal.

But I can't do this. Besides the command line "issued" by eclipse uses
-nx which tells eclipse to not read any command from .gdbinit file!

Does anyone here have used eclipse for such purpose that could perhaps help?

Thank you.

red floyd

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Jul 19, 2021, 8:56:12 PM7/19/21

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Have you tried starting the program in a terminal, and then attaching
the eclipse debugger to the PID of that process?

Paulo da Silva

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Jul 19, 2021, 9:25:31 PM7/19/21

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Às 01:55 de 20/07/21, red floyd escreveu:

How do I do that?
Insert some sleep at the beginning, launch it and then use "Attach to
Application" in the Debug Configurations?
I'll try that, but it's weird for a thing that should be simple.
Thanks

Paulo da Silva

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Jul 19, 2021, 9:33:23 PM7/19/21

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Às 02:25 de 20/07/21, Paulo da Silva escreveu:

> Às 01:55 de 20/07/21, red floyd escreveu:
>> On 7/19/2021 12:15 PM, Paulo da Silva wrote:
>>> Hi!

>...

>>
>> Have you tried starting the program in a terminal, and then attaching
>> the eclipse debugger to the PID of that process?
>>
> How do I do that?
> Insert some sleep at the beginning, launch it and then use "Attach to
> Application" in the Debug Configurations?
> I'll try that, but it's weird for a thing that should be simple.
> Thanks
>

It failed!
A popup message appears:

Error in final launch sequence:

Failure to attach to process: testC [56830]
Error:
Failed to execute MI command:
-target-attach 56830

Error message from debugger back end:
ptrace: Operação não permitida. (Tr. from pt: Operation not
allowed/permited)

Öö Tiib

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Jul 20, 2021, 6:36:52 AM7/20/21

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Perhaps your IDE is misconfigured. Debugger must be set up
there:
<https://help.eclipse.org/2021-06/index.jsp?topic=%2Forg.eclipse.cdt.debug.application.doc%2Ftasks%2Fcdt_t_run_dbg.htm>

Paulo da Silva

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Jul 21, 2021, 1:31:44 PM7/21/21

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Às 02:33 de 20/07/21, Paulo da Silva escreveu:

Ok, to fix this:
Change in /etc/sysctl.d/10-ptrace.conf
kernel.yama.ptrace_scope = 1
to
kernel.yama.ptrace_scope = 0

Besides, one needs to put, for example, getchar(); at the beginning of
the program for it to wait the debugger attach. Then just hit enter and
the debugging should proceed normally.

A very weird solution, however!!

Regards

red floyd

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Jul 21, 2021, 9:02:45 PM7/21/21

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You could put "break main" in your .gdbinit file. Then it will break at
main automatically.

Paulo da Silva

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Jul 22, 2021, 12:16:46 PM7/22/21

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Às 02:02 de 22/07/21, red floyd escreveu:

> On 7/21/2021 10:31 AM, Paulo da Silva wrote:
>> Às 02:33 de 20/07/21, Paulo da Silva escreveu:
>>> Às 02:25 de 20/07/21, Paulo da Silva escreveu:
>>>> Às 01:55 de 20/07/21, red floyd escreveu:
>>>>> On 7/19/2021 12:15 PM, Paulo da Silva wrote:
>>>>>> Hi!
...

>>> Error message from debugger back end:
>>> ptrace: Operação não permitida. (Tr. from pt: Operation not
>>> allowed/permited)
>>>
>> Ok, to fix this:
>> Change in /etc/sysctl.d/10-ptrace.conf
>> kernel.yama.ptrace_scope = 1
>> to
>> kernel.yama.ptrace_scope = 0
>>
>> Besides, one needs to put, for example, getchar(); at the beginning of
>> the program for it to wait the debugger attach. Then just hit enter and
>> the debugging should proceed normally.
>>
>> A very weird solution, however!!
>>
>> Regards
>>
>
>
> You could put "break main" in your .gdbinit file. Then it will break at
> main automatically.
>

You are missing the point that the program is launched outside
eclipse/gdb. So it runs ... Later we attach to it from eclipse. So, we
need to force it "to wait" for us to attach to it.

Besides, the eclipse issues a call to gdb using -nx. This means no
.gdbinit is executed.

Regards

red floyd

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Jul 22, 2021, 1:38:54 PM7/22/21

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Couldn't you run under gdb in the terminal, break at main, and then
detach once you've attached Eclipse?

Paulo da Silva

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Jul 22, 2021, 8:19:02 PM7/22/21

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Às 18:38 de 22/07/21, red floyd escreveu:

I didn't test, but may be. Neverthless, for repeated lauches, it may not
be wothwhile.
I'll see ...

Thanks