Re: [PATCHv4] gdb/python/mi: create MI commands using python

[Jan Vrany <jan.vrany@labware.com>]

On Fri, 2022-02-25 at 12:22 -0700, Tom Tromey wrote:
> > > > > > "Andrew" == Andrew Burgess via Gdb-patches <gdb-patches@sourceware.org> writes:
> 
> Andrew> This v4 patch is identical to the version I posted here:
> Andrew>   
> https://urldefense.proofpoint.com/v2/url?u=https-3A__sourceware.org_pipermail_gdb-2Dpatches_2022-2DFebruary_185821.html&d=DwIBAg&c=sPZ6DeHLiehUHQWKIrsNwWp3t7snrE-az24ztT0w7Jc&r=WpFFGgYa98Yp-c29WHTCwU1wAGFBvszA6a4RzgpMSqc&m=WKDSYr2J171tvbvDjhBen4GJ7U_Ub6ZV_q_Nyl7TQb8&s=Yz53CWD-zdMB2I_L-G0Xai7hGsPlRXGOkvDDoaMoy3c&e=
> 
> Andrew> except I've rebased onto current master.  I just wanted to make sure
> Andrew> it was clear what the latest version of this patch was.
> 
> Thank you both for working on this.
> 
> Andrew> When used within gdb the above command produced output like this:
> Andrew>   (gdb)
> Andrew>   -echo-args a b c
> Andrew>   ^done,args=["a","b","c"]
> Andrew>   (gdb)
> 
> Not necessary for this patch but I wonder if there should also be a way
> to emit an async event from Python.

This is on my list already but I decided leave this for later patch. 
I have not even started working on this as to not having too many balls
in the air. 

> 
> Andrew> I have required that the fields names used in mi result output must
> Andrew> follow C identifier restrictions (i.e. must match the regexp
> Andrew> "[a-zA-Z][a-zA-Z0-9_]*").
> 
> I think '-' is also supported, e.g.:
> 
>       uiout->field_string ("thread-id", print_thread_id (thr));
> 
> Andrew> +@defun MICommand.invoke (arguments)
> Andrew> +This method is called by @value{GDBN} when the new MI command is
> Andrew> +invoked.
> Andrew> +
> Andrew> +@var{arguments} is a list of strings.  Note, that @code{--thread}
> Andrew> +and @code{--frame} arguments are handled by @value{GDBN} itself therefore
> Andrew> +they do not show up in @code{arguments}.
> 
> I guess this is done because an option may or may not take a value?
> That kind of too bad since it would be nice if this could just be a
> dictionary.
> 
> I suppose we could always also add an MI parsing helper, though Python
> also has tons of things for this as well.
> 
> Andrew> +The strings used for @emph{VARIABLE} names in the @sc{GDB/MI} output
> Andrew> +must follow the following rules; the string must be at least one
> Andrew> +character long, the first character must be in the set
> Andrew> +@code{[a-zA-Z]}, while every subsequent character must be in the set
> Andrew> +@code{[a-zA-Z0-9_]}.
> 
> This should be updated to include '-'.
> 
> Andrew> +@smallexample
> Andrew> +class MIEcho(gdb.MICommand):
> Andrew> +    """Echo arguments passed to the command."""
> Andrew> +
> Andrew> +    def __init__(self, name, mode, toplevel = None):
> Andrew> +        self._mode = mode
> Andrew> +        super(MIEcho, self).__init__(name, toplevel)
> 
> What is 'toplevel' here?  It isn't documented for gdb.MICommand.
> 
> Andrew> +  /* Called when the MI command is invoked.  */
> Andrew> +  virtual void do_invoke(struct mi_parse *parse) const override;
> 
> Andrew> +      if (key_repr != nullptr)
> Andrew> +	key_repr_string = python_string_to_target_string (key_repr.get ());
> Andrew> +      if (key_repr_string == nullptr)
> Andrew> +	gdbpy_handle_exception ();
> Andrew> +
> Andrew> +      gdbpy_error (_("non-string object used as key: %s"),
> Andrew> +		   key_repr_string.get ());
> 
> Someday I'd like gdb to solve the "denaturation" problem, where if
> Python code throw some exception, it's turned into a generic exception
> of some kind by gdb ... which if it is then caught again by Python, has
> transmuted into something else.
> 
> Anyway this seems fine, just felt like I had to get that out.
> 
> Andrew> +    for (; *name != '\0'; ++name)
> Andrew> +      if (!isalnum (*name) && *name != '_')
> Andrew> +	return false;
> 
> '-'
> 
> Andrew> +  else if (PyIter_Check (result))
> Andrew> +    {
> Andrew> +      gdbpy_ref<> item;
> Andrew> +      ui_out_emit_list list_emitter (uiout, field_name);
> Andrew> +      while (true)
> Andrew> +	{
> 
> Not for this patch but I wonder if emitting dictionaries via ui_out
> might make for nicer CLI commands sometimes.
> 
> Andrew> +  gdbpy_enter enter_py (get_current_arch (), current_language);
> 
> Probably should just drop the parameters here.
> 
> thanks,
> Tom