simplify IO::Storable.make_null, fixes IO::Storable warning on empty - …

…fix #448

Changes

@@ -9,6 +9,7 @@
 - fix modulo for ulonglong and on Windows
 - update Opt::Simplex docs (#452) - thanks @KJ7LNW
 - fix Graphics::OpenGLQ on MacOS Ventura (#452) - thanks @deriamis
+- fix IO::Storable warning on empty (#448) - thanks @djerius for report
 
 2.084 2023-05-21
 - reduce size of PDL_KLUDGE_COPY_X macro to <4096 in line with C standard, to fix for older clang on many BSD

IO/Storable/storable.pd

@@ -36,16 +36,8 @@ void
 make_null(sv)
         SV *sv
         CODE:
-        /* we basically mimic pdl_null but without letting
-         * it give us a it->sv ! We have our own to which we
-         * connect below
-         */
         pdl *it = PDL->pdlnew();
         if (!it) PDL->pdl_barf("Failed to create new pdl");
-	it->datatype = PDL_B;
-	it->data = PDL->smalloc((STRLEN) (PDL->howbig(it->datatype)));
-        it->datasv = newSVpv(it->data,PDL->howbig(it->datatype));
-        it->data = SvPV_nolen((SV *)it->datasv);
         /* connect pdl struct to this sv */
         sv_setiv(SvRV(sv),PTR2IV(it));
         it->sv = SvRV(sv);

IO/Storable/t/storable.t

@@ -16,7 +16,12 @@ $serialized = freeze $x;
 $oldx = thaw $serialized;
 # $oldx->dump;
 
-ok(sum(abs($x-$oldx))==0, 'PDL freeze/thaw');
+is sum(abs($x-$oldx)), 0, 'PDL freeze/thaw';
+
+$x = double '1';
+$serialized = freeze $x;
+$dthaw = thaw $serialized;
+is $dthaw, $x, 'PDL freeze/thaw of PDL scalar';
 
 # $oldb = thaw $serialized;
 # $oldc = thaw $serialized;
@@ -49,7 +54,7 @@ $pfreeze = $phash->freeze;
 $phthaw = thaw $pfreeze;
 
 ok(all($phthaw == $phash), 'PDL has-a works with freeze/thaw');
-ok(UNIVERSAL::isa($phthaw,'HASH'), 'PDL is a hash');
+isa_ok($phthaw,'HASH', 'PDL is a hash');
 
 # Test that freeze + thaw results in new object
 $seq1 = sequence(3);
@@ -66,6 +71,12 @@ $seq2->slice('2') .= 8;
 ok(! all($seq2 == $seq2_dc), 'Initialization from dclone object') or
     diag($seq2, $seq2_dc);
 
+{
+  my @w;
+  local $SIG{__WARN__} = sub { push @w, @_ };
+  thaw( freeze pdl([]) );
+  is "@w", '', 'no warnings';
+}
 
 # Now test reading from files
 testLoad($_) foreach( qw(t/storable_new_amd64.dat t/storable_old_amd64.dat) );