Re: [PATCH] gdb: add support for %V to printf command

[Tom Tromey <tom@tromey.com>]

>>>>> "Andrew" == Andrew Burgess via Gdb-patches <gdb-patches@sourceware.org> writes:

Andrew> This commit adds a new format for the printf and dprintf commands:
Andrew> '%V'.  This new format takes any GDB expression and formats it as a
Andrew> string, just as GDB would for a 'print' command, e.g.:

Thank you for doing this.  I'm definitely a fan of the idea.

Andrew> --- a/gdb/printcmd.c
Andrew> +++ b/gdb/printcmd.c
Andrew> @@ -2733,7 +2733,7 @@ ui_printf (const char *arg, struct ui_file *stream)
Andrew>    if (*s++ != '"')
Andrew>      error (_("Bad format string, missing '\"'."));
 
Andrew> -  format_pieces fpieces (&s);
Andrew> +  format_pieces fpieces (&s, false, true);

I was going to ask if there is a spot that sets gdb_extensions=false and
the new flag=true.  This setting seems odd to me, but I didn't dig
through to find out why it's needed.

Andrew> +	      string_file buffer;
Andrew> +	      print_formatted (val_args[i], 0, &print_opts, &buffer);
Andrew> +	      gdb_puts (buffer.string ().c_str ());

Why is a second stream needed here?  Like, couldn't print_formatted be
called with 'stream'?  Wouldn't that preserve any styling done by
print_formatted?  Or is the intention to strip styling?

Andrew> +	    if (f[1] == '[')
Andrew> +	      {
Andrew> +		const char *tmp;
Andrew> +		for (tmp = f; *tmp != ']' && *tmp != '\0'; ++tmp)
Andrew> +		  ;
Andrew> +		if (*tmp == ']')
Andrew> +		  f = tmp;

strchr if it simplifies things.

I didn't dig into this either, but I don't think %V could work in
dprintf's call or agent modes.  So, maybe gdb should reject this
somewhere.  Or maybe this is already done by the default setting in the
constructor?

Tom