repeat command on return after issuing guile command

repeat command on return after issuing guile command

[David Boles]

I have recently been learning to use the guile mechanism for extending gdb’s capabilities - very powerful. One thing that I have noticed is that after a “guile (…)” command is issued, the normal behavior of gdb re-performing the last command executed if you just hit enter is disabled. This applies to even native gdb commands like “next” or “step” - which is quite painful.

I have observed this with versions 7.10.x and 7.12.1.

Any insights would be appreciated.

Thx,

 - db

Re: repeat command on return after issuing guile command

[Eli Zaretskii]

> From: David Boles <boles@ieee.org>
> Date: Fri, 28 Apr 2017 22:50:18 -0500
> 
> I have recently been learning to use the guile mechanism for extending gdb’s capabilities - very powerful. One thing that I have noticed is that after a “guile (…)” command is issued, the normal behavior of gdb re-performing the last command executed if you just hit enter is disabled. This applies to even native gdb commands like “next” or “step” - which is quite painful.
> 
> I have observed this with versions 7.10.x and 7.12.1.

I cannot reproduce this with GDB 7.12 built with Guile 2.0.X.  I tried
this:

  (gdb) apropos file
  ... long list of commands ...
  (gdb) <press RET>
  ... the same long list of commands ...
  (gdb) guile (display (+ 20 3)) (newline)
  23
  (gdb) apropos file
  ... long list of commands ...
  (gdb) <press RET>
  ... the same long list of commands ...

So it seems to work as expected for me.  Can you show a recipe that
exhibits the problem on your system?

Re: repeat command on return after issuing guile command

[Matt Rice]

On Sun, Apr 30, 2017 at 12:03 PM, Eli Zaretskii <eliz@gnu.org> wrote:
>> From: David Boles <boles@ieee.org>
>> Date: Fri, 28 Apr 2017 22:50:18 -0500
>>
>> I have recently been learning to use the guile mechanism for extending gdb’s capabilities - very powerful. One thing that I have noticed is that after a “guile (…)” command is issued, the normal behavior of gdb re-performing the last command executed if you just hit enter is disabled. This applies to even native gdb commands like “next” or “step” - which is quite painful.
>>
>> I have observed this with versions 7.10.x and 7.12.1.
>
> I cannot reproduce this with GDB 7.12 built with Guile 2.0.X.  I tried
> this:
>
>   (gdb) apropos file
>   ... long list of commands ...
>   (gdb) <press RET>
>   ... the same long list of commands ...
>   (gdb) guile (display (+ 20 3)) (newline)
>   23
>   (gdb) apropos file
>   ... long list of commands ...
>   (gdb) <press RET>
>   ... the same long list of commands ...
>
> So it seems to work as expected for me.  Can you show a recipe that
> exhibits the problem on your system?

One thing that I can think of is if the guile script being executed
causes the program to continue,
which then hits a breakpoint which has "commands" associated with it,
the call to prevent_dont_repeat in
breakpoint.c (bpstat_do_actions_1), could have some clobbering effect
messes with the repeat.

I cannot seem reproduce such behavior though

using the following foo.gdb:
set breakpoint pending on
break foo
commands 1
  print "foo"
end
guile (use-modules (gdb))
guile (execute "start")
guile (execute "cont")

$ echo "void foo() {}; int main() { while (1) foo(); return 0; }" |
gcc -g -x c - && gdb -quiet ./a.out -ex 'source foo.gdb'
Reading symbols from ./a.out...done.
Breakpoint 1 at 0x4004aa: file <stdin>, line 1.
Breakpoint 1, foo () at <stdin>:1
1    in <stdin>
$1 = "foo"
(gdb) guile (execute "cont")
Breakpoint 1, foo () at <stdin>:1
1    in <stdin>
$2 = "foo"
(gdb)
Breakpoint 1, foo () at <stdin>:1
1    in <stdin>
$3 = "foo"
(gdb)

Re: repeat command on return after issuing guile command

[David Boles]

My apologies - I never run gdb outside of Emacs and made the assumption
that an interaction between the gdb-mi.el code, guile, and command
repeating wasn't plausible.

The problem indeed does not occur with gdb itself, only when run from
within emacs.

I will go and investigate things from the Emacs side of things and try
to develop a patch for this behavior.

Thanks for setting me straight.

 - db

On Mon, May 1, 2017, at 06:20 AM, Matt Rice wrote:
> On Sun, Apr 30, 2017 at 12:03 PM, Eli Zaretskii <eliz@gnu.org> wrote:
> >> From: David Boles <boles@ieee.org>
> >> Date: Fri, 28 Apr 2017 22:50:18 -0500
> >>
> >> I have recently been learning to use the guile mechanism for extending gdb’s capabilities - very powerful. One thing that I have noticed is that after a “guile (…)” command is issued, the normal behavior of gdb re-performing the last command executed if you just hit enter is disabled. This applies to even native gdb commands like “next” or “step” - which is quite painful.
> >>
> >> I have observed this with versions 7.10.x and 7.12.1.
> >
> > I cannot reproduce this with GDB 7.12 built with Guile 2.0.X.  I tried
> > this:
> >
> >   (gdb) apropos file
> >   ... long list of commands ...
> >   (gdb) <press RET>
> >   ... the same long list of commands ...
> >   (gdb) guile (display (+ 20 3)) (newline)
> >   23
> >   (gdb) apropos file
> >   ... long list of commands ...
> >   (gdb) <press RET>
> >   ... the same long list of commands ...
> >
> > So it seems to work as expected for me.  Can you show a recipe that
> > exhibits the problem on your system?
> 
> One thing that I can think of is if the guile script being executed
> causes the program to continue,
> which then hits a breakpoint which has "commands" associated with it,
> the call to prevent_dont_repeat in
> breakpoint.c (bpstat_do_actions_1), could have some clobbering effect
> messes with the repeat.
> 
> I cannot seem reproduce such behavior though
> 
> using the following foo.gdb:
> set breakpoint pending on
> break foo
> commands 1
>   print "foo"
> end
> guile (use-modules (gdb))
> guile (execute "start")
> guile (execute "cont")
> 
> $ echo "void foo() {}; int main() { while (1) foo(); return 0; }" |
> gcc -g -x c - && gdb -quiet ./a.out -ex 'source foo.gdb'
> Reading symbols from ./a.out...done.
> Breakpoint 1 at 0x4004aa: file <stdin>, line 1.
> Breakpoint 1, foo () at <stdin>:1
> 1    in <stdin>
> $1 = "foo"
> (gdb) guile (execute "cont")
> Breakpoint 1, foo () at <stdin>:1
> 1    in <stdin>
> $2 = "foo"
> (gdb)
> Breakpoint 1, foo () at <stdin>:1
> 1    in <stdin>
> $3 = "foo"
> (gdb)