Re: [PATCH v2] gdb: add tutorial command

[Guinevere Larsen <guinevere@redhat.com>]

On 1/24/26 8:41 AM, Hannes Domani wrote:
>   Am Donnerstag, 22. Januar 2026 um 21:30:04 MEZ hat Guinevere Larsen <guinevere@redhat.com> Folgendes geschrieben:
>
>> Before this commit, there is little way for a new user to learn how to
>> use GDB on their own.  The documentation contains an example session,
>> but that isn't contained in GDB itself, and the "help" and "apropos"
>> commands exist, but they aren't the best to really teach what GDB can
>> do, only to describe commands on their own.
>>   
>> This commit changes this by introducing a command called "tutorial",
>> which takes a page out of common design from the last few decades and
>> provides a self-contained tutorial for users, walking them through a
>> simple bug in C code, and explaining several commands in context.
>>   
>> The tutorial is mostly implemented (ab)using the before_prompt hook to
>> print the messages, so that users can have completion, history and so
>> on, and it is implemented in python to make maintaining it in the future
>> as simple as possible.
>> ---
>> +def cleanup():
>> +    print(
>> +        """
>> +Thank you for taking this tutorial.  We hope it has been
>> +helpful for you.  If you found any bugs or would like to
>> +provide feedback, feel free to send do so through IRC, in
>> +the #gdb room of libera.chat, or send an email to
>> +gdb@sourceware.org.
>> +To recap, these were the commands explained in the tutorial
>> +  * shell
> The shell command was not explained.
Good point. It is also pretty advanced, I guess I can just remove from 
here.
>
>
>> +  * file
>> +  * start
>> +  * continue
>> +  * list
>> +  * break
>> +  * print
>> +  * step
>> +  * next
>> +  * display
>> +  * watch
>> +  * quit
I suppose I didn't explain quit anymore? I'll double check and possibly 
remove this as well.
>> +  * help
>> +  """
>> +    )
>> +    gdb.events.before_prompt.disconnect(tutorial_hook)
>> +    gdb.events.exited.disconnect(tutorial_exit_hook)
>> +    # Clean up example code.
> At the end of the tutorial I get this warning:
> warning: BFD: reopening /home/src/a.out: No such file or directory
>
> I've silenced it by adding this line here:
>      gdb.execute("file")
>
> But then I get these warnings instead:
> Error in re-setting breakpoint 2: No source file named example_code.c.
> Error in re-setting breakpoint 3: No symbol table is loaded.  Use the "file" command.
>
> So I've also added this line before the other:
>      gdb.execute("delete breakpoints")
>
> Then all warnings were gone.

These warnings happen when the target is mourning the inferior (ie, 
making an internal cleanup of stuff). I don't understand all the cleanup 
that GDB has to do, so I don't know if deleting all breakpoints is 
enough or if we're still leaving cruft behind

In a 1:1 meeting with Andrew, he suggested instead that cleanup could be 
called in the next "before_prompt" hook instead, so we're guaranteed to 
have finished the internal cleanup but we do it before the user can 
actually do anything.

-- 
Cheers,
Guinevere Larsen
It/she

>
>
>> +    try:
>> +        f = open(generated_code)
>> +        f.close()
>> +        os.remove(generated_code)
>> +    except FileNotFoundError:
>> +        # File doesn't exist, nothing to do.
>> +        pass
>> +    try:
>> +        f = open(generated_binary)
>> +        f.close()
>> +        os.remove(generated_binary)
>> +    except FileNotFoundError:
>> +        # File doesn't exist, nothing to do.
>> +        pass
>> +
>
> Hannes
>