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Postings from January 2003
Nicholas Clark <nick@unfortu.net> writes:
>Sorry about the delay in replying to the original question.
>On Wed, Dec 11, 2002 at 11:28:48AM -0500, John Peacock wrote:
>> Rafael Garcia-Suarez wrote:
>> >%_ : placeholder for an SV that will get stringified. See sv_vcatpvfn() in
>> >sv.c.
>> >I can't find doc on this in the perl sources, but there a small paragraph
>> >about it in the Cozens & Jenness.
>
>I can't find any docs either. In fact, a straight grep on %_ in the
>current sources is most unrewarding.
>
>> Neat! Is it supported in 5.005???
IIRC Chip put it in way back.
>
>Well, I had a grep in the 5.004_04 sources and it's in there quite a lot,
>such as:
>
> if (in_eval & 2)
> warn("%_", msg);
> else if (in_eval)
> sv_catsv(GvSV(errgv), msg);
>
>so I wondered what had happened to them all. The same piece of code is now:
>
> if (PL_in_eval & EVAL_WARNONLY)
> Perl_warn(aTHX_ "%"SVf, msg);
> else
> qerror(msg);
>
>with this in perl.h
>
>#ifndef SVf
># ifdef CHECK_FORMAT
># define SVf "p"
># else
># define SVf "_"
># endif
>#endif
>
>That doesn't seem to be in Devel::PPort (yet - patches welcome I guess)
>
>I wonder how many parts of the perl core can be reduced slightly in size
>by changing %s SvPV_nolen(sv) to %_ sv.
>This would have the beneficial side effect of making the non-error code path
>more direct, which might have a slight speed gain.
Again IIRC I thought that %_ was not quite the same as %s-of-PV.
That is I seem to recall one motivation for put it in was to avoid stringifying
things that were SvNOK and do %g on those and %ld on SvIOK - thuse there
might be spots where changing to %_ would change what you got.
>
>It's not in 5.003_07's sources, but I don't think anyone really supports that
>any more.
>
>Nicholas Clark
--
Nick Ing-Simmons
http://www.ni-s.u-net.com/