Add MAYBE_DEREF_GV macro

There are so many parts of the core (mostly pp functions or functions
they call) that need a glob or a globref, including many that call
get-magic at the wrong time (or not at all in some cases, that it
makes sense to add a macro to do it.

It can be used like this:

   if (gv = MAYBE_DEREF_GV(sv)) /* calls get-magic */
   {

   }
   else { /* avoid magic here */

   }

1 files changed, 13 insertions, 0 deletions

diff --git a/pp.h b/pp.h
index 0ba877f22a..b6798ead34 100644
--- a/pp.h
+++ b/pp.h
@@ -496,12 +496,25 @@ True if this op will be the return value of an lvalue subroutine
   )
 
 #ifdef PERL_CORE
+
 /* These are just for Perl_tied_method(), which is not part of the public API.
    Use 0x04 rather than the next available bit, to help the compiler if the
    architecture can generate more efficient instructions.  */
 #  define TIED_METHOD_MORTALIZE_NOT_NEEDED	0x04
 #  define TIED_METHOD_ARGUMENTS_ON_STACK	0x08
 #  define TIED_METHOD_SAY			0x10
+
+/* Used in various places that need to dereference a glob or globref */
+#  define MAYBE_DEREF_GV(sv)                                       \
+    (                                                               \
+	SvGETMAGIC(sv),                                              \
+	isGV_with_GP(sv)                                              \
+	  ? (GV *)sv                                                   \
+	  : SvROK(sv) && (SvGETMAGIC(SvRV(sv)), isGV_with_GP(SvRV(sv))) \
+	     ? (GV *)SvRV(sv)                                            \
+	     : NULL                                                       \
+    )
+
 #endif
 
 /*