RT#54600 - Devel::NYTProf Dev

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Message from discussion RT#54600
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Sender: Tim Bunce <tim.bu...@gmail.com>
Date: Tue, 16 Feb 2010 17:50:40 +0000
From: Tim Bunce <Tim.Bu...@pobox.com>
To: develnytprof-dev@googlegroups.com
Subject: Re: [develnytprof-dev: 1676] RT#54600
Message-ID: <20100216175040.GO...@timac.local>
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 <20100216161200.GG49...@plum.flirble.org>
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Thanks for background detail and test Nick. Very helpful.
I'll give it some thought, hopefully tonight.

Tim.

On Tue, Feb 16, 2010 at 04:12:00PM +0000, Nicholas Clark wrote:
> On Tue, Feb 16, 2010 at 03:44:52PM +0000, codesite-nore...@google.com wrote:
> > Revision: 1056
> > Author: n...@ccl4.org
> > 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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