On Tue, Feb 16, 2010 at 03:44:52PM +0000, [email protected] wrote:
> Revision: 1056
> Author: [email protected]
> Date: Tue Feb 16 07:44:10 2010
> Log: Better test for RT#54600
>
> The problem is caused by S_call_body() in 5.8.8 and earlier making a direct
> call to Perl_pp_entersub(), rather than indirecting via
> PL_ppaddr[OP_ENTERSUB].
> Hence any calls made through it (such as DESTROY) never reach our
> pp_subcall_profiler, and subr_entry_setup() is never called to initialse
> subr_entry_ix. Hence if if the DESTROY routine (or an AUTOLOAD called in
> lieu
> of it) executes goto \&subname; that does reach pp_subcall_profiler, which
> assumes that it must (already) be inside a subroutine.
>
> I don't (yet) know what the right fix (or work around) is.
> http://code.google.com/p/perl-devel-nytprof/source/detail?r=1056
Specifically, I can see this comment:
/* goto &sub opcode acts like a return followed by a call all in one.
* When this op starts executing, the 'current' subr_entry that was
* pushed onto the savestack by pp_subcall_profiler will be
'already_counted'
* so the profiling of that call will be handled naturally for us.
* So far so good.
* Before it gets destroyed we'll take a copy of the subr_entry.
* Then tell subr_entry_setup() to use our copy as a template so it'll
* seem like the sub we goto'd was called by the same sub that called
* the one that executed the goto. Except that we do use the fid:line
* of the goto statement. That way the call graph makes sense and the
* 'calling location' make sense. Got all that?
*/
I assume that the work around is that if we arrive at a goto &sub
with subr_entry_ix 0, we skip the copy part, and treat it as an entersub
(possibly at the line of the goto, given that we can infer that it won't
be possible to merge the timing back to the location of the caller of
the original subroutine).
But I'm not sure of the right way to do that.
Nicholas Clark
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