Re: [PATCH v3 3/4] gdb/cli: add '.' as an argument for 'list' command

[Keith Seitz <keiths@redhat.com>]

On 6/21/23 03:45, Bruno Larsen via Gdb-patches wrote:
> Currently, after the user has used the list command once, there is no
> way to ask GDB to print the location where the inferior is stopped.
> This commit adds a way to do that using '.' as a new argument for the
> 'list' command.  If the inferior isn't running, the command throws an
> error.  The test gdb.base/list.exp was updated to test this new argument.

I'm not entirely sure how I feel about throwing an error when using
"list ." with no running inferior. Can you explain why that might be
preferable to, say, just mimicking "list" with no argument or some other
fallback?

[I'm not going to NACK this patch for this, of course. I am just normally
cautious about adding errors when logical, convenient fallbacks could
be used instead.]

However, there is a problem that specifically needs addressing IMO.

Compare (using gdb debugging gdb):

(top-gdb) list 10
5	
6	   This program is free software; you can redistribute it and/or modify
7	   it under the terms of the GNU General Public License as published by
8	   the Free Software Foundation; either version 3 of the License, or
9	   (at your option) any later version.
10	
11	   This program is distributed in the hope that it will be useful,
12	   but WITHOUT ANY WARRANTY; without even the implied warranty of
13	   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
14	   GNU General Public License for more details.
(top-gdb)
15	
16	   You should have received a copy of the GNU General Public License
17	   along with this program.  If not, see <http://www.gnu.org/licenses/>.  */
18	
19	#include "defs.h"
20	#include "main.h"
21	#include "interps.h"
22	
23	int
24	main (int argc, char **argv)
(top-gdb)
25	{
26	  struct captured_main_args args;
27	
28	  memset (&args, 0, sizeof args);
29	  args.argc = argc;
30	  args.argv = argv;
31	  args.interpreter_p = INTERP_CONSOLE;
32	  return gdb_main (&args);
33	}
(top-gdb)


With (after "start"):

(top-gdb) list .
23	int
24	main (int argc, char **argv)
25	{
26	  struct captured_main_args args;
27	
28	  memset (&args, 0, sizeof args);
29	  args.argc = argc;
30	  args.argv = argv;
31	  args.interpreter_p = INTERP_CONSOLE;
32	  return gdb_main (&args);
(top-gdb)
23	int
24	main (int argc, char **argv)
25	{
26	  struct captured_main_args args;
27	
28	  memset (&args, 0, sizeof args);
29	  args.argc = argc;
30	  args.argv = argv;
31	  args.interpreter_p = INTERP_CONSOLE;
32	  return gdb_main (&args);
(top-gdb)
23	int
24	main (int argc, char **argv)
25	{
26	  struct captured_main_args args;
27	
28	  memset (&args, 0, sizeof args);
29	  args.argc = argc;
30	  args.argv = argv;
31	  args.interpreter_p = INTERP_CONSOLE;
32	  return gdb_main (&args);
(top-gdb)

I don't think this is particularly user-friendly. Is it possible to make
the two use cases behave similarly?

Keith