On Sat, Jun 04, 2005 at 04:46:38PM -0700, Michael G Schwern wrote:
> On Sat, Jun 04, 2005 at 10:52:20PM -0000, Sebastian wrote:
> > Test case: perl -le 'sub a { print exists $_[0] } a(undef); a($f = undef);'
> > Problem: Using exists() on @_ does not work as expected with undef
>
> This sheds some light on the problem. They definately contain different
> structures. Don't know if Devel::Peek simply can't read the former @_ magic
> in element 0 or if there's simply nothing there.
exists() on an array is just a hack that checks whether the element is
&PL_sv_undef or some other SV (which may or may not have an undef value).
foo(undef) manages to the set the element to &PL_sv_undef.
Can't really be fixed short of using some other static SV to mark unused
elements (cf PL_sv_placeholder), but personally I think that's throwing
good money after bad.
--
Technology is dominated by two types of people: those who understand what
they do not manage, and those who manage what they do not understand.
