in reply to Re^3: Why reftype and blessed are making my life harder than it needs to be
in thread Why reftype and blessed are making my life harder than it needs to be

Interestingly, reftype only checks the length of ref, which is why it can probably be fooled by "\0".

You are looking at the perl implementation, which isn't quite what i would consider to the canonical implementation. IMO the canonical implementation is the XS one: 

char *
reftype(sv)
    SV * sv
PROTOTYPE: $
CODE:
{
    if (SvMAGICAL(sv))
    mg_get(sv);
    if(!SvROK(sv)) {
    XSRETURN_UNDEF;
    }
    RETVAL = sv_reftype(SvRV(sv),FALSE);
}
OUTPUT:
    RETVAL

[download]

In Data::Dump::Streamer its implemented as 

char *
reftype(sv)
    SV * sv
PROTOTYPE: $
CODE:
{
    if (SvMAGICAL(sv))
    mg_get(sv);
    if(!SvROK(sv)) {
    XSRETURN_NO;
    } else {
        RETVAL = sv_reftype(SvRV(sv),FALSE);
    }
}
OUTPUT:
    RETVAL

[download]

Notice the only difference is the XSRETURN_NO; versus XSRETURN_UNDEF;. With the benefit of experience IMO the use of XSRETURN_UNDEF; was a mistake. I've said as much on p5p a number of times, but without much response. I guess it would be too dangerous a change, which is why im going to be providing patches to implement _reftype() so you can say 

if (_reftype($foo) eq $TYPE) { ... }

[download]

without worrying about warnings. Of course if you don't want to wait, you can always 

use Data::Dump::Streamer qw(reftype);

[download]

And get the more practical implementation Right Now. :-)

---
$world=~s/war/peace/g

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Re^5: Why reftype and blessed are making my life harder than it needs to be (XS/_reftype)
by dragonchild (Archbishop) on Feb 10, 2006 at 14:13 UTC
    Unfortunately, Data::Dump::Streamer is 5.6+ (though you don't have a "use 5.006;" line before your "use warnings;" line). This came up in the context of me helping JHUCKABY with DBM::Deep and I want to keep DBM::Deep able to run with older Perls.

    It seems sad, though, that reftype() won't be patched to XSRETURN_NO, especially as that makes more sense. Also, why can't the Perl version be patched to at least return !!0 instead of explicit undef?

    My criteria for good software:
    1. Does it work?
    2. Can someone else come in, make a change, and be reasonably certain no bugs were introduced?
[reply]

      It seems sad, though, that reftype() won't be patched to XSRETURN_NO, especially as that makes more sense. Also, why can't the Perl version be patched to at least return !!0 instead of explicit undef?

      XSRETURN_NO is how you do return !!0 in XS.

      And the answer I think is here: 

      D:\dev\>perl -e"print defined !!0"
1

      [download]

      But Im hopeful that the p5p powers that be will be receptive of the idea of a _reftype() sub that returns PL_no instead of Pl_undef. (Which is what XSRETURN_NO and XSRETURN_UNDEF do.)

      ---
      $world=~s/war/peace/g

[reply]
[d/l]
        That's a good thing, at least for reftype(). I can see wanting to return undef from blessed() because you can bless into the empty string. But, the empty string is the representation for one of the 8 Perl scalar types. Or, am I just completely confused?
        My criteria for good software:
        1. Does it work?
        2. Can someone else come in, make a change, and be reasonably certain no bugs were introduced?
[reply]

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