Re: [PATCH/RFA] Introduce new $_isvoid() convenience function

[Doug Evans <dje@google.com>]

On Thu, Sep 12, 2013 at 1:11 PM, Sergio Durigan Junior
<sergiodj@redhat.com> wrote:
> gdb/
> 2013-09-12  Sergio Durigan Junior  <sergiodj@redhat.com>
>
>         * NEWS: Mention new convenience function $_isvoid.
>         * value.c (isvoid_internal_fn): New function.
>         (_initialize_values): Add new convenience function $_isvoid.
>
> gdb/doc/
> 2013-09-12  Sergio Durigan Junior  <sergiodj@redhat.com>
>
>         * gdb.texinfo (Convenience Functions): Mention new convenience
>         function $_isvoid.
>
> gdb/testsuite/
> 2013-09-12  Sergio Durigan Junior  <sergiodj@redhat.com>
>
>         * gdb.base/gdbvars.exp (test_convenience_functions): New
>         function.  Call it.

Hi.  Thanks for persevering!

While I often follow "it's easier to relax restrictions than impose
them after the fact",
in this case I wonder if there's any reason to restrict $_isvoid() to
convenience variables.

Thoughts?

For "void foo(){}", is there any real difference to:
(gdb) set $foo = foo()
(gdb) p $_isvoid($foo)
(gdb) p $_isvoid(foo())

[Haven't tried it, but I'm guessing removing the internalva4 check in
your patch would make that work.]

Also, you've put  a fair bit of time into this, and I'm happy with
what you've got.  And thanks!
The high order bit here for me is being able to script $_exitcode + $exitsignal.
If we're going with checking for a void value, one could just leave it
to be handled in Python.
OTOH, this patch is really simple, and IMO it is *nice* to be able to
do this from just a plain gdb script,
so I'm advocating accepting this patch (modulo maybe handling any void
value, not just conv vars).

btw, I noticed that if I run a program to exit, and then rerun to
main, $_exitcode has the last exit code - I would have expected it to
get reset to void upon rerun.  After all, if I stop at main the first
time through, $_exitcode is void.
[I'll file a bug, no need to address this in your patch series.]