From 6c692eb49735ae6901652a974eb76e2a0c36dfae Mon Sep 17 00:00:00 2001
From: Ed J <mohawk2@users.noreply.github.com>
Date: Fri, 10 Jan 2025 23:18:47 +0000
Subject: [PATCH] overloaded operators now throw exception if given undef
 argument - #519

---
 Changes       |  1 +
 lib/PDL/PP.pm | 24 +++++++++++++++++-------
 t/ops.t       |  5 +++++
 3 files changed, 23 insertions(+), 7 deletions(-)

diff --git a/Changes b/Changes
index 4d2ef6383..0c9b0b3ca 100644
--- a/Changes
+++ b/Changes
@@ -14,6 +14,7 @@
 - InplaceDoc now automatically generated like BadDoc, Signature doc includes types
 - Overload key added to PP (#519)
 - "usage" section of xform docs now automatically generated (#519)
+- overloaded operators now throw exception if given undef argument (#519) - thanks @cgtinney for report
 
 2.098 2025-01-03
 - fix Windows build problems
diff --git a/lib/PDL/PP.pm b/lib/PDL/PP.pm
index 188b94eac..20e6ba8d7 100644
--- a/lib/PDL/PP.pm
+++ b/lib/PDL/PP.pm
@@ -1441,25 +1441,35 @@ $PDL::PP::deftbl =
        my $fullname = $::PDLOBJ."::$name";
        if ($one_arg) {
          $ret .= pp_line_numbers(__LINE__, <<EOF);
-use overload '$op' => sub { $fullname(\$_[0]) };
+use overload '$op' => sub {
+  Carp::confess("$fullname: overloaded '$op' given undef")
+    if grep !defined, \$_[0];
+  $fullname(\$_[0]);
+};
 EOF
        } else {
          $ret .= pp_line_numbers(__LINE__, <<EOF);
 {
   my (\$foo, \$overload_sub);
   use overload '$op' => \$overload_sub = sub(;\@) {
-      return $fullname($bitwise_passon) unless ref \$_[1]
-              && (ref \$_[1] ne '$::PDLOBJ')
-              && defined(\$foo = overload::Method(\$_[1], '$op'))
-              && \$foo != \$overload_sub; # recursion guard
-      goto &\$foo;
+    Carp::confess("$fullname: overloaded '$op' given undef")
+      if grep !defined, \@_[0,1];
+    return $fullname($bitwise_passon) unless ref \$_[1]
+            && (ref \$_[1] ne '$::PDLOBJ')
+            && defined(\$foo = overload::Method(\$_[1], '$op'))
+            && \$foo != \$overload_sub; # recursion guard
+    goto &\$foo;
   };
 }
 EOF
        }
        $ret .= pp_line_numbers(__LINE__, <<EOF) if $mutator;
 # in1, in2, out, swap if true
-use overload '$op=' => sub { $fullname(\$_[0]->inplace, \$_[1]); \$_[0] };
+use overload '$op=' => sub {
+  Carp::confess("$fullname: overloaded '$op=' given undef")
+    if grep !defined, \@_[0,1];
+  $fullname(\$_[0]->inplace, \$_[1]); \$_[0]
+};
 EOF
        $::PDLOVERLOAD .= "$ret}\n";
        my @args = @{ $sig->args_callorder };
diff --git a/t/ops.t b/t/ops.t
index 8cd13b7de..b4d80de3f 100644
--- a/t/ops.t
+++ b/t/ops.t
@@ -182,6 +182,11 @@ is $@, '', 'inplace += worked';
 is $pa.'', 2, 'inplace += right value after';
 }
 
+eval { my $res = pdl(3) + undef };
+like $@, qr/given undef/, 'error on overloaded op with undef arg';
+eval { (my $t = pdl(3)) += undef };
+like $@, qr/given undef/, 'error on overloaded op= with undef arg';
+
 {
 # log10 now uses C library
 # check using scalars and ndarrays