[perl #129916] Allow sub-in-stash outside of main

The sub-in-stash optimization introduced in 2eaf799e only applied to
subs in the main stash, not in other stashes, due to a problem with
the logic in newATTRSUB.

This comment:

	   Also, we may be called from load_module at run time, so
	   PL_curstash (which sets CvSTASH) may not point to the stash the
	   sub is stored in.

explains why we need the PL_curstash != CopSTASH(PL_curcop) check.
(Perl_load_module will fail without it.) But that logic does not work
properly at compile time (when PL_curcop == &PL_compiling).

The value of CopSTASH(&PL_compiling) is never actually used.  It is
always set to the main stash.  So if we check that PL_curstash !=
CopSTASH(PL_curcop) and forego the optimization in that case, we will
never optimize subs outside of the main stash.

What we really need is to check IN_PERL_RUNTIME && PL_curstash !=
opSTASH(PL_curcop).  I.e., forego the optimization at run time if the
stashes differ.  That is what this commit implements.

One observable side effect of this change is that deleting a stash
element no longer anonymizes the CV if the CV had no GV that it was
depending on to provide its name.  Since the main thing in such situa-
tions is that we do not get a crash, I think this change (arguably an
improvement) is acceptable.)

-----------

A bit of explanation of various other changes:

gv.c:require_tie_mod needed a bit of help, since it could not handle
sub refs in stashes.

To keep localisation of stash elements working the same way,
local($Stash::{foo}) now upgrades a coderef to a full GV before the
localisation.  (Changes in two pp*.c files and in scope.c:save_gp.)

t/op/stash.t contains a test that makes sure that perl does not crash
when a GV with a CV pointing to it gets deleted.  This commit tweaks
the test so that it continues to test that.  (There has to be a GV for
the test to test what it is meant to test.)

Similarly with t/uni/caller.t and t/uni/stash.t.

op.c:rv2cv_op_cv with the _MAYBE_NAME_GV flag was returning the cal-
ling GV in those cases where a GV-less sub is called via a GV.  E.g.,
*main = \&Foo::foo; main().  This meant that errors like ‘Not enough
arguments’ were giving the wrong sub name.

newATTRSUB was not calling mro_method_changed_in when storing a
sub as an RV.

gv_init needs to arrange for the new GV to have the file and line num-
ber corresponding to the sub in it.  These are taken from CvSTART,
which may be off by a few lines, but is the closest we have to the
place the sub was declared.

2 files changed, 5 insertions, 1 deletions

diff --git a/t/uni/caller.t b/t/uni/caller.t
index de314b0a31..c48018c1ee 100644
--- a/t/uni/caller.t
+++ b/t/uni/caller.t
@@ -26,6 +26,9 @@ sub { @c = caller(0) } -> ();
 
 # Bug 20020517.003 (#9367), used to dump core
 sub ｆｏｏ { @c = caller(0) }
+# The subroutine only gets anonymised if it is relying on a real GV
+# for its name.
+() = *{"ｆｏｏ"}; # with quotes so that the op tree doesn’t reference the GV
 my $fooref = delete $ｍａｉｎ::{ｆｏｏ};
 $fooref -> ();
 ::is( $c[3], "ｍａｉｎ::__ANON__", "deleted subroutine name" );
@@ -55,6 +58,7 @@ sub { ｆ() } -> ();
 ::ok( $c[4], "hasargs true with anon sub" );
 
 sub ｆｏｏ2 { ｆ() }
+() = *{"ｆｏｏ2"}; # see ｆｏｏ notes above
 my $fooref2 = delete $ｍａｉｎ::{ｆｏｏ2};
 $fooref2 -> ();
 ::is( $c[3], "ｍａｉｎ::__ANON__", "deleted subroutine name" );
diff --git a/t/uni/stash.t b/t/uni/stash.t
index 31d6c9d9b2..e329faab25 100644
--- a/t/uni/stash.t
+++ b/t/uni/stash.t
@@ -170,7 +170,7 @@ plan( tests => 49 );
             package ＦŌŌ３;
             sub 남えㄉ {};
             my $anon = sub {};
-            my $남えㄉ = eval q[\&남えㄉ];
+            my $남えㄉ = eval q[*남えㄉ{CODE}]; # not \&남えㄉ; need a real GV
             package main;
             delete $ＦŌŌ３::{남えㄉ}; # make named anonymous