Re: [RFC 3/8] Add output styles to gdb

[Tom Tromey <tom@tromey.com>]

>>>>> "Simon" == Simon Marchi <simark@simark.ca> writes:

Simon> Ok, so I'd like to understand better the idea of the format-based
Simon> approach, maybe I don't quite get what you mean.  It would be easier
Simon> to comment on something concrete (even without code, just a relatively
Simon> well-defined description of the format).

The minimum, I think, is to have something that encompasses the
formatting, but not the titling, emitted by table headers.  So instead
of:

  uiout->table_header (10, ui_left, "refcount", "Refcount");

the example I gave said

  "{refcount<10}"

where the idea is that "refcount" is the field name, "<" says to
left-justify, and "10" is the field size.  I pictured using ">" for
right justification, and something like "|" for center and ":" or "="
for "none".

Anything outside of {} would be plain text that is just emitted
directly.

Exactly how to spell the formatting can be debated, like should there
be a lead-in character ("set extended-prompt" uses backslash, C uses %).

So, something like maintenance_info_bfds currently reads:

  ui_out_emit_table table_emitter (uiout, 3, -1, "bfds");
  uiout->table_header (10, ui_left, "refcount", "Refcount");
  uiout->table_header (18, ui_left, "addr", "Address");
  uiout->table_header (40, ui_left, "filename", "Filename");

... but in the format approach the first 2 arguments of each call could
be removed.

Then when printing the body:

  ui_out_emit_tuple tuple_emitter (uiout, NULL);
  uiout->field_int ("refcount", gdata->refc);
  uiout->field_string ("addr", host_address_to_string (abfd));
  uiout->field_string ("filename", bfd_get_filename (abfd));
  uiout->text ("\n");

Here the ->text call could be removed and the text put into the format
string.


I didn't do an exhaustive survey of lists or tuples in the way that I
looked at tables.  There are probably difficult cases lurking in there,
just as there were for tables.  And, the difficult table cases remain
unsolved -- I haven't really given them much thought.

Maybe another tricky case is handling indentation of elided stack
frames.


Something I like about the approach I implemented is that it's
relatively easy to explain and use.

The upside of the foramtting approach is that it gives more power to
users.  For example maybe there are things that are currently hidden
behind mi-like-p that could be exposed; or at least users could arrange
to drop fields they are not interested in.

Tom