Make SvIsCOW honest about globs

SvIsCOW was ignoring the fact that it might be passed a
typeglob, which made its behaviour contradict its docs.

This fixes that and, in doing so, simplifies the
upcoming Internals::SvREADONLY fix.

2 files changed, 20 insertions, 0 deletions

diff --git a/ext/XS-APItest/APItest.xs b/ext/XS-APItest/APItest.xs
index acd1b5e42f..68533da58b 100644
--- a/ext/XS-APItest/APItest.xs
+++ b/ext/XS-APItest/APItest.xs
@@ -2858,6 +2858,13 @@ CODE:
 	HeVAL(entry) = NULL;
     }
 
+bool
+SvIsCOW(SV *sv)
+CODE:
+    RETVAL = SvIsCOW(sv);
+OUTPUT:
+    RETVAL
+
 MODULE = XS::APItest		PACKAGE = XS::APItest::Magic
 
 PROTOTYPES: DISABLE
diff --git a/ext/XS-APItest/t/sviscow.t b/ext/XS-APItest/t/sviscow.t
new file mode 100644
index 0000000000..bcc9da8ebd
--- /dev/null
+++ b/ext/XS-APItest/t/sviscow.t
@@ -0,0 +1,13 @@
+use strict;
+use warnings; no warnings 'once';
+
+use Test::More tests => 1;
+
+use XS::APItest;
+use Hash::Util 'lock_value';
+
+my %h;
+$h{g} = *foo;
+lock_value %h, 'g';
+
+ok(!SvIsCOW($h{g}), 'SvIsCOW is honest when it comes to globs');