There's no such thing as a SvUV. A ref can be in practically any type of SV (at least SvIV, SvNV, SvPV, SvPVIV, SvPVNV). 

>perl -MDevel::Peek -e"my $x = {}; Dump($x);"
SV = IV(0x3269b8) at 0x3269c0
  REFCNT = 1
  FLAGS = (PADMY,ROK)
  ...

>perl -MDevel::Peek -e"my $x = 'abc'; $x = {}; Dump($x);"
SV = PV(0x33abe0) at 0x2a69d0
  REFCNT = 1
  FLAGS = (PADMY,ROK)
  ...

>perl -MDevel::Peek -e"my $x = 'abc'; $x = 123; $x = {}; Dump($x);"
SV = PVIV(0x28da78) at 0x2a6a60
  REFCNT = 1
  FLAGS = (PADMY,ROK)
  ...

[download]

A reference is indicated by the ROK flag. The pointers of references are neither IV nor UV. The pointers are returned as SV* as they should. The actual pointer is located in the same location as an IV's number or UV's number, so ROK && IOK is impossible.

illguts

Update: It appears possible to have an SV that is both ROK and IOK. It would have to be hand-crafted; Perl never constructs one. No idea if it's safe to construct one.

In reply to Re: SvUV vs SvIV for pointers in SVs, typemap by ikegami
in thread SvUV vs SvIV for pointers in SVs, typemap by patcat88

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