Re: [PATCH 2/4] Show new created display

[Pedro Alves <palves at redhat dot com>]

On 04/28/2014 07:12 AM, Yao Qi wrote:
> When I run refactored unavailable.exp, I find
> command display behaves a little different on live inferior and on
> examining traceframes.  In live inferior, when command "display argc"
> is typed, the value of "argc" is shown.
> 
> (gdb) display argc
> 1: argc = 1 '\001'
> 
> however, on tfile target, when command "display argc" is typed, the
> value of "argc" is not shown.
> 
> (gdb) tfind
> Found trace frame 0, tracepoint 1
>     at ../../../../git/gdb/testsuite/gdb.trace/unavailable.cc:198
> 198       i =  (int) argc + argi + argf + argd + argstruct.memberi + argarray[1];
> (gdb) display argc
> 
> I also notice that on "core" target, the value of "argc" isn't shown
> either.  This difference is caused by the code below in printcmd.c:display_command,
> 
>       if (from_tty && target_has_execution)
>         do_one_display (new);
> 
> Looks the value of each display is shown if the target has execution.
> Source code archaeology doesn't tell much about this requirement.
> However, if we type command "display" then on "core" or "tfile"
> target, the value of "argc" is still displayed,

Maybe ancient, ancient code that tried to prevent "display $pc"
from erroring out?

Judging from doing that when there's execution, and then
killing the inferior, and getting:

 (gdb) display
 1: $pc = <error: No registers.>

Looks like we handle errors fine here, so I see no issue.

I assume that if there's no target pushed yet, we'll now
see that error -- it's fine with me.

It would be good if display.exp itself was augmented to explicitly
test this.  Say, do "display global" (where global is a variable that
is initialized to something not zero), and also "display $pc" before
there's execution.

> This patch is to remove the checking to target_has_execution from the
> condition.

OK.

-- 
Pedro Alves