Stop tell($glob_copy) from clearing PL_last_in_gv

This bug is a side effect of rv2gv’s starting to return an incoercible
mortal copy of a coercible glob in 5.14:

$ perl5.12.4 -le 'open FH, "t/test.pl"; $fh=*FH; tell $fh; print tell'
0
$ perl5.14.0 -le 'open FH, "t/test.pl"; $fh=*FH; tell $fh; print tell'
-1

In the first case, tell without arguments is returning the position of
the filehandle.

In the second case, tell with an explicit argument that happens to
be a coercible glob (tell has an implicit rv2gv, so tell $fh is actu-
ally tell *$fh) sets PL_last_in_gv to a mortal copy thereof, which is
freed at the end of the statement, setting PL_last_in_gv to null.  So
there is no ‘last used’ handle by the time we get to the tell without
arguments.

This commit adds a new rv2gv flag that tells it not to copy the glob.

By doing it unconditionally on the kidop, this allows tell(*$fh) to
work the same way.

Let’s hope nobody does tell(*{*$fh}), which will unset PL_last_in_gv
because the inner * returns a mortal copy.

This whole area is really icky.  PL_last_in_gv should be refcounted,
but that would cause handles to leak out of scope, breaking programs
that rely on the auto-closing ‘feature’.

1 files changed, 1 insertions, 1 deletions

diff --git a/ext/B/B/Concise.pm b/ext/B/B/Concise.pm
index cc2c87debb..f3b517ac78 100644
--- a/ext/B/B/Concise.pm
+++ b/ext/B/B/Concise.pm
@@ -612,7 +612,7 @@ $priv{$_}{4} = "DREFed" for (qw(rv2sv rv2av rv2hv));
 @{$priv{$_}}{32,64,96} = ("DREFAV", "DREFHV", "DREFSV")
   for (qw(rv2gv rv2sv padsv aelem helem));
 $priv{$_}{16} = "STATE" for ("padav", "padhv", "padsv");
-$priv{rv2gv}{4} = "NOINIT";
+@{$priv{rv2gv}}{4,16} = qw "NOINIT FAKE";
 @{$priv{"entersub"}}{1,4,16,32,64} = qw( INARGS TARG DBG DEREF );
 @{$priv{rv2cv}}{1,8,128} = ("CONST","AMPER","NO()");
 $priv{"gv"}{32} = "EARLYCV";