Fix uniqint SIGSEGV for objects with no int overload

In case uniqint takes several objects, it always tries to call their
int overload using amagic_call.  This patch fixes the case when
amagic_call returned NULL resulting into Segmentation Violation.
Several tests are also added to ensure proper objects handling.

Signed-off-by: Sergei Zhmylev <[email protected]>

Author: zhmylove

ListUtil.xs

@@ -1369,8 +1369,10 @@ CODE:
             /* coerce to integer */
 #if PERL_VERSION >= 8
             /* int_amg only appeared in perl 5.8.0 */
-            if(SvAMAGIC(arg) && (arg = AMG_CALLun(arg, int)))
-                ; /* nothing to do */
+            if(SvAMAGIC(arg)) {
+                if(!(arg = AMG_CALLun(arg, int)))
+                    croak("No \"int\" method found in overloaded package");
+            }
             else
 #endif
             if(!SvOK(arg) || SvNOK(arg) || SvPOK(arg))

t/uniq.t

@@ -3,7 +3,7 @@
 use strict;
 use warnings;
 use Config; # to determine ivsize
-use Test::More tests => 31;
+use Test::More tests => 35;
 use List::Util qw( uniqstr uniqint uniq );
 
 use Tie::Array;
@@ -98,6 +98,32 @@ is_deeply( [ uniqint 6.1, 6.2, 6.3 ],
                'uniqint on undef coerces to zero' );
 }
 
+{
+    use Math::BigInt;
+    my ($obj1, $obj2, $obj3) = map { Math::BigInt->new($_) } 1, 1, 2;
+
+    is_deeply( [ uniqint $obj1, $obj1 ],
+               [ $obj1 ],
+               'uniqint removes repeated Math::BigInt objects' );
+
+    is_deeply( [ uniqint $obj1, $obj2 ],
+               [ $obj1 ],
+               'uniqint removes subsequent Math::BigInt objects' );
+
+    is_deeply( [ uniqint $obj1, $obj2, $obj3 ],
+               [ $obj1, $obj3 ],
+               'uniqint removes multiple subsequent Math::BigInt objects' );
+}
+
+{
+    { package OverloadedPackageWithoutInt; use overload "+" => sub {} }
+
+    my $obj1 = bless {}, "OverloadedPackageWithoutInt";
+
+    ok( !defined eval { uniqint $obj1 },
+        'package with no "int" overload throws exception' );
+}
+
 SKIP: {
     skip('UVs are not reliable on this perl version', 2) unless "$]" >= 5.008000;