From 8af39ba74a9e314e52254f5e7d4dd646c6a6e622 Mon Sep 17 00:00:00 2001
From: Ed J <mohawk2@users.noreply.github.com>
Date: Tue, 1 Feb 2022 22:05:01 +0000
Subject: [PATCH] passing null as input param now an error

---
 Basic/Core/Core.pm           |  1 +
 Basic/Core/pdlthread.c       |  5 +++++
 Basic/Primitive/primitive.pd | 17 +++++++++++++++++
 Changes                      |  1 +
 t/01-pptest.t                | 14 ++++++++++++--
 t/core.t                     |  8 ++++++++
 t/primitive.t                |  6 ++++++
 7 files changed, 50 insertions(+), 2 deletions(-)

diff --git a/Basic/Core/Core.pm b/Basic/Core/Core.pm
index 1d01f9a05..a56000411 100644
--- a/Basic/Core/Core.pm
+++ b/Basic/Core/Core.pm
@@ -463,6 +463,7 @@ a single Empty PDL, you get back the Empty PDL (no padding).
 =for ref
 
 Returns a 'null' ndarray.
+It is an error to pass one of these as an input to a function.
 
 =for usage
 
diff --git a/Basic/Core/pdlthread.c b/Basic/Core/pdlthread.c
index 16a2b47ee..85b126460 100644
--- a/Basic/Core/pdlthread.c
+++ b/Basic/Core/pdlthread.c
@@ -247,6 +247,11 @@ pdl_error pdl_dim_checks(
       ));
     } else {
       PDL_Indx *dims = pdl->dims;
+      if (pdl->state & PDL_NOMYDIMS)
+        return pdl_make_error(PDL_EUSERERROR,
+          "Error in %s: input parameter '%s' is null\n",
+          vtable->name, vtable->par_names[i]
+        );
       if (ninds > 0 && ndims < ninds) {
 	/* Dimensional promotion when number of dims is less than required: */
 	for (j=0; j<ninds; j++) {
diff --git a/Basic/Primitive/primitive.pd b/Basic/Primitive/primitive.pd
index 5dbba742d..61babcd18 100644
--- a/Basic/Primitive/primitive.pd
+++ b/Basic/Primitive/primitive.pd
@@ -1649,6 +1649,23 @@ pp_def('append',
 # note that ideally we want to say '$SIZE(mn) = $SIZE(m)+$SIZE(n);'
 # but that requires placing RedoDimsParsedCode *after* assignment of
 # childdims to $SIZE(XXX)!!!  XXXXXmake that workXXXXX
+        PMCode => pp_line_numbers(__LINE__-1, '
+sub PDL::append {
+  my ($i1, $i2, $o) = map PDL->topdl($_), @_;
+  if (grep $_->isempty, $i1, $i2) {
+    if (!defined $o) {
+      return $i2->copy if $i1->isempty;
+      return $i1->isnull ? PDL->zeroes(0) : $i1->copy;
+    } else {
+      $o .= $i2->isnull ? PDL->zeroes(0) : $i2, return $o if $i1->isempty;
+      $o .= $i1->isnull ? PDL->zeroes(0) : $i1, return $o;
+    }
+  }
+  $o //= PDL->null;
+  PDL::_append_int($i1, $i2, $o);
+  $o;
+}
+        '),
 	RedoDimsCode => '
 		pdl * dpdla = $PDL(a);
 		pdl * dpdlb = $PDL(b);
diff --git a/Changes b/Changes
index dba2d7a41..b11ea6967 100644
--- a/Changes
+++ b/Changes
@@ -1,4 +1,5 @@
 - PDL::Complex no longer undefs PDL::i
+- passing null as input param now an error
 
 2.072 2022-01-30
 - fix bug in qsortveci that broke PDL::VectorValued - thanks @zmughal for report
diff --git a/t/01-pptest.t b/t/01-pptest.t
index 54d9568cc..b203e8d76 100644
--- a/t/01-pptest.t
+++ b/t/01-pptest.t
@@ -129,6 +129,14 @@ pp_deft('fooseg',
 	   loop(n) %{ $b() = $a(); %}
 ');
 
+# adapted from PDL::NDBin: if in=null and b is a scalar, was SEGV-ing
+pp_deft( '_flatten_into',
+        Pars => "in(m); indx b(m); [o] idx(m)",
+        Code => '
+                loop(m) %{ $idx() = $in(); %}
+        ',
+);
+
 pp_addhdr << 'EOH';
 void tinplace_c1(int n, PDL_Float* data);
 void tinplace_c2(int n, PDL_Float* data1, PDL_Float* data2);
@@ -300,16 +308,18 @@ is( join(',',$x->dims), "10" );
 ok( tapprox($x,sequence(10)) );
 
 # this used to segv under solaris according to Karl
-{ no warnings 'uninitialized';
+{
   my $ny=7;
   $x = double xvals zeroes (20,$ny);
   test_fooseg $x, $y=null;
-
   ok( 1 );  # if we get here at all that is alright
   ok( tapprox($x,$y) )
     or diag($x, "\n", $y);
 }
 
+eval { test__flatten_into(null, 2) };
+ok 1; #was also segfaulting
+
 # test the bug alluded to in the comments in
 # pdl_changed (pdlapi.c)
 # used to segfault
diff --git a/t/core.t b/t/core.t
index dfab4fbc9..9f31b2d2c 100644
--- a/t/core.t
+++ b/t/core.t
@@ -117,6 +117,14 @@ do {
 $x = pdl(pdl(5));
 ok all( $x== pdl(5)), "pdl() can piddlify an ndarray";
 
+$x = pdl(null);
+is_deeply [$x->dims], [0], 'pdl(null) gives empty' or diag "x(", $x->info, ")";
+ok !$x->isnull, 'pdl(null) gives non-null' or diag "x(", $x->info, ")";
+
+$x = pdl(null, null);
+is_deeply [$x->dims], [0,2], 'pdl(null, null) gives empty' or diag "x(", $x->info, ")";
+ok !$x->isnull, 'pdl(null, null) gives non-null' or diag "x(", $x->info, ")";
+
 # pdl of mixed-dim pdls: pad within a dimension
 $x = pdl( zeroes(5), ones(3) );
 ok all($x == pdl([0,0,0,0,0],[1,1,1,0,0])),"Piddlifying two ndarrays concatenates them and pads to length" or diag("x=$x\n");
diff --git a/t/primitive.t b/t/primitive.t
index 2acf2e1c9..540d4b0b1 100644
--- a/t/primitive.t
+++ b/t/primitive.t
@@ -293,6 +293,12 @@ ok($a1->at($x->list,$y->list,$z->list,$w->list) == 203, "whichND" );
 $a1 = pdl(1,2,3,4);
 my $b1 = append($a1,2);
 ok(int(sum($b1))==12, "append");
+$b1 = append(null, null);
+ok !$b1->isnull, 'append(null, null) returns non-null';
+ok $b1->isempty, 'append(null, null) returns an empty';
+append(null, null, $b1);
+ok !$b1->isnull, 'append(null, null, b1) sets non-null';
+ok $b1->isempty, 'append(null, null, b1) sets an empty';
 
 # clip tests
 ok(tapprox($im->hclip(5)->sum,83), "hclip" );