[perl #77684] Restore the 5.10/12 behaviour of open $fh, ">", \$glob_copy

This restores the perl 5.10/12 behaviour, making open treat \$foo as a
scalar reference if it is a glob copy (SvFAKE).

It also fixes an existing assertion failure that the test now trig-
gers. PerlIOScalar_pushed was not downgrading the sv before set-
ting SvCUR.

1 files changed, 11 insertions, 1 deletions

diff --git a/t/io/open.t b/t/io/open.t
index 01bfaca73f..5bbcb0b59b 100644
--- a/t/io/open.t
+++ b/t/io/open.t
@@ -10,7 +10,7 @@ $|  = 1;
 use warnings;
 use Config;
 
-plan tests => 110;
+plan tests => 111;
 
 my $Perl = which_perl();
 
@@ -337,3 +337,13 @@ fresh_perl_is(
     ',
     'ok', { stderr => 1 },
     '[perl #77492]: open $fh, ">", \*glob causes SEGV');
+
+# [perl #77684] Opening a reference to a glob copy.
+{
+    my $var = *STDOUT;
+    open my $fh, ">", \$var;
+    print $fh "hello";
+    is $var, "hello", '[perl #77684]: open $fh, ">", \$glob_copy'
+        # when this fails, it leaves an extra file:
+        or unlink \*STDOUT;
+}