sv_num*: correctly handle "0+" overloaded values

do_ncmp() expects simple SVs and for overloaded SVs will just compare
the SvNV() of each SV, mishandling the case where the 0+ overload
returns a large UV or IV that isn't exactly representable as an NV.

# Conflicts:
#	ext/XS-APItest/t/sv_numeq.t
#	ext/XS-APItest/t/sv_numne.t
#	sv.c

Author: tonycoz

ext/XS-APItest/t/sv_numcmp.t

@@ -1,6 +1,6 @@
 #!perl
 
-use Test::More tests => 17;
+use Test::More tests => 24;
 use XS::APItest;
 use Config;
 use strict;
@@ -62,3 +62,23 @@ is sv_numcmp_flags($1, 10, SV_GMAGIC), 0, 'sv_numecmp_flags with SV_GMAGIC does'
       'AlwaysTen is not 10 with SV_SKIP_OVERLOAD';
 }
 
+# +0 overloading with large numbers and using fallback
+{
+    my $big = ~0;
+    my $bigm1 = $big-1;
+    package MyBigNum {
+        use overload "0+" => sub { $_[0][0] },
+          fallback => 1;
+    }
+    my $o1 = bless [ $big   ], "MyBigNum";
+    my $o2 = bless [ $big   ], "MyBigNum";
+    my $o3 = bless [ $bigm1 ], "MyBigNum";
+
+    is $o1 <=> $o2,     0, "perl op gets it right";
+    is $o1 <=> $bigm1,  1, "perl op still gets it right for left overload";
+    is $o1 <=> $o3,     1, "perl op still gets it right for different values";
+    is sv_numcmp($o1, $o2),    0, "sv_numcmp two overloads";
+    is sv_numcmp($o1, $o3),    1, "sv_numcmp two different overloads";
+    is sv_numcmp($o1, $big),   0, "sv_numcmp left overload";
+    is sv_numcmp($bigm1, $o3), 0, "sv_numcmp right overload";
+}

ext/XS-APItest/t/sv_numeq.t

@@ -1,6 +1,6 @@
 #!perl
 
-use Test::More tests => 15;
+use Test::More tests => 22;
 use XS::APItest;
 use Config;
 
@@ -47,4 +47,24 @@ ok  sv_numeq_flags($1, 10, SV_GMAGIC), 'sv_numeq_flags with SV_GMAGIC does';
     ok !sv_numeq_flags($obj, 10, SV_SKIP_OVERLOAD), 'AlwaysTen is not 10 with SV_SKIP_OVERLOAD'
 }
 
+# +0 overloading with large numbers and using fallback
+{
+    my $big = ~0;
+    my $bigm1 = $big-1;
+    package MyBigNum {
+        use overload "0+" => sub { $_[0][0] },
+          fallback => 1;
+    }
+    my $o1 = bless [ $big   ], "MyBigNum";
+    my $o2 = bless [ $big   ], "MyBigNum";
+    my $o3 = bless [ $bigm1 ], "MyBigNum";
 
+    ok $o1 == $o2, "perl op gets it right";
+    ok $o1 == $big, "perl op still gets it right for left overload";
+    ok !($o1 == $o3), "perl op still gets it right for different values";
+    ok sv_numeq($o1, $o2), "sv_numeq two overloads";
+    ok !sv_numeq($o1, $o3), "sv_numeq two different overloads"
+      or diag sprintf "%x vs %x", $o1, $o3;
+    ok sv_numeq($o1, $big), "sv_numeq left overload";
+    ok sv_numeq($bigm1, $o3), "sv_numeq right overload";
+}

ext/XS-APItest/t/sv_numne.t

@@ -1,6 +1,6 @@
 #!perl
 
-use Test::More tests => 15;
+use Test::More tests => 22;
 use XS::APItest;
 use Config;
 
@@ -45,3 +45,24 @@ ok !sv_numne_flags($1, 11, SV_GMAGIC), 'sv_numne_flags with SV_GMAGIC does';
 
     ok !sv_numne_flags($obj, 11, SV_SKIP_OVERLOAD), 'AlwaysTwelve is 12 with SV_SKIP_OVERLOAD'
 }
+
+# +0 overloading with large numbers and using fallback
+{
+    my $big = ~0;
+    my $bigm1 = $big-1;
+    package MyBigNum {
+        use overload "0+" => sub { $_[0][0] },
+          fallback => 1;
+    }
+    my $o1 = bless [ $big   ], "MyBigNum";
+    my $o2 = bless [ $big   ], "MyBigNum";
+    my $o3 = bless [ $bigm1 ], "MyBigNum";
+
+    ok !($o1 != $o2), "perl op gets it right";
+    ok $o1 != $bigm1, "perl op still gets it right for left overload";
+    ok $o1 != $o3, "perl op still gets it right for different values";
+    ok !sv_numne($o1, $o2), "sv_numne two overloads";
+    ok sv_numne($o1, $o3), "sv_numne two different overloads";
+    ok !sv_numne($o1, $big), "sv_numne left overload";
+    ok !sv_numne($bigm1, $o3), "sv_numne right overload";
+}

sv.c

@@ -8721,11 +8721,16 @@ S_sv_numcmp_common(pTHX_ SV **sv1, SV **sv2, const U32 flags,
     if(!*sv2)
         *sv2 = &PL_sv_undef;
 
-    /* FIXME: do_ncmp doesn't handle "+0" overloads well */
     if(!(flags & SV_SKIP_OVERLOAD) &&
-       (SvAMAGIC(*sv1) || SvAMAGIC(*sv2)) &&
-       (*result = amagic_call(*sv1, *sv2, method, 0))) {
-        return true;
+       (SvAMAGIC(*sv1) || SvAMAGIC(*sv2))) {
+        if ((*result = amagic_call(*sv1, *sv2, method, 0)))
+            return true;
+
+        /* normally handled by try_amagic_bin */
+        if (SvROK(*sv1))
+            *sv1 = sv_2num(*sv1);
+        if (SvROK(*sv2))
+            *sv2 = sv_2num(*sv2);
     }
 
     return false;