Re: Add a way to invoke redefined (overridden) GDB commands

[Marco Barisione <mbarisione@undo.io>]

On 20 Oct 2020, at 16:06, Pedro Alves <pedro@palves.net> wrote:
> On 10/19/20 8:28 PM, Marco Barisione wrote:
>> On 19 Oct 2020, at 19:47, Philippe Waroquiers <philippe.waroquiers@skynet.be> wrote:
> 
>>> I am wondering how rename will interact with alias:
>>> alias are resolved at definition time, so a rename
>>> following an alias might not have the expected effect.
>> 
>> That’s a very good point. I didn’t consider aliases and hooks.
>> 
>> My use case is for building on top of existing commands so they can
>> be extended/tweaked.  Aliases and hooks need to follow the new
>> command, including the ones set by users (so I have no way of knowing
>> about them).
>> I can’t think of any way of making a rename command work like this.
>> 
>> Any idea?
> 
> In my previous example, where it read:
> 
> (gdb) rename run org_run
> (gdb) define run
> ...
> 
> merge those two commands into a single atomic operation?
> 
> Like:
> 
> (gdb) rename-define run org_run
>> echo Will run!\n
>> org_run
>> end
> (gdb) run
>  Will run!
>  [... normal output of run ...]
> (gdb) org_run
>  [... normal output of run ...]
> 
> Unlike "rename", "rename-define" (strawman name) would take care
> of moving the alias and pre/post hooks to the new implementation.


I can’t think of any good name for a command so maybe it should just
be an option to define?

    (gdb) define -rename-existing orig_run run
    echo Will run\n
    orig_run
    end

Or "define -r" for short.

GDB would not ask if you want to redefine the existing command as I
think that the user’s intention would be quite clear.

Similarly, in Python we could have a "rename_existing" argument to
gdb.Command.__init__ ().


"rename" still seems useful, but hooks/aliases would follow the
rename:

    (gdb) define foo
    echo Hello world\n
    end
    (gdb) alias my-alias = foo
    (gdb) rename foo bar
    (gdb) bar
    Hello world
    (gdb) foo
    Undefined command: “foo".  Try "help”.
    (gdb) my-alias
    Hello world

I think that rename with an "=" would be a bit confusing and would
not provide a way of deleting commands (unlike rename in TCL).


What do you think?


-- 
Marco Barisione