[Python-Dev] seeing off SET_LINENO

[Michael Hudson]

Tim Peters <tim.one@comcast.net> writes:

> [Michael Hudson]
> > I've found another annoying problem.  I'm not really expecting someone
> > here to sovle it for me, but writing it down might help me think
> > clearly.
> >
> > This is about the function epilogues that always get generated.  I.e:
[snip example]
> > You can see here that the epilogue gets associated with line 3,
> > whereas it shouldn't really be associated with any line at all.
> 
> It has to be associated with some line >= 3, as c_lnotab isn't capable of
> expressing anything other than that.

Yes.

> It *could* associate it with "line 4", though, if the compiler were
> changed to pump out another c_lntab entry at the epilogue.  That
> would be better than saying the time is charged to line 3, since it
> isn't on line 3 then.  I'd be happy to trade away total insanity for
> partial insanity <wink>.

This would be bad if you had

def f():
    print 1
def g():
    print 2

Anyway, I think I've found a way to get around this (see the patch).

> It stops on the "if a:" for me twice today, and I doubt that's any less
> confusing.  If it were set to line 4 instead, an unaltered pdb would
> presumably show a blank line (whatever) after the function body, and an
> altered pdb could be taught that "the last line" c_lnotab claims exists is
> really devoted to exit code not associated with any source-file line.

Yes.  I didn't really like the idea of heavily hacking pdb, as I don't
understand it.

Cheers,
M.

-- 
39. Re graphics:  A picture is worth 10K words - but only those
    to describe the picture.  Hardly any sets of 10K words can be
    adequately described with pictures.
  -- Alan Perlis, http://www.cs.yale.edu/homes/perlis-alan/quotes.html