SvREFCNT_inc(cv) recursive subs

A CXt_SUB context frame owns 1 reference count to the CV being called,
but only if it's the bottom-level call to that CV; recursive calls don't
count.

This commit changes it so that every CXt_SUB frame owns a reference count.

This removes a lot of "if (CvDEPTH(cv) < 2)" type tests from the code and
makes things generally simpler and less bug-prone.

For ordinary (non-recursive) sub calls it will now be slightly faster, as
it no longer has to do the CvDEPTH check on sub entry and exit; for subs
being recursed into, it will probably be slightly slower, as although it
no longer has to the CvDEPTH check on entry and exit, it now has to do a
refcnt ++/-- instead.

This also means that a deeply recursing sub will have a very high ref
count; but there is no new additional danger of overflow, as sv_refcnt is
U32 while xcv_depth is I32: so the latter will still overflow earlier
anyway.

1 files changed, 0 insertions, 5 deletions

diff --git a/pp_sort.c b/pp_sort.c
index 51742f6c35..ace0a0559e 100644
--- a/pp_sort.c
+++ b/pp_sort.c
@@ -1672,11 +1672,6 @@ PP(pp_sort)
 	    PUSHBLOCK(cx, CXt_NULL, PL_stack_base);
 	    if (!(flags & OPf_SPECIAL)) {
 		cx->cx_type = CXt_SUB;
-		/* If our comparison routine is already active (CvDEPTH is
-		 * is not 0),  then PUSHSUB does not increase the refcount,
-		 * so we have to do it ourselves, because the LEAVESUB fur-
-		 * ther down lowers it. */
-		if (CvDEPTH(cv)) SvREFCNT_inc_simple_void_NN(cv);
 		PUSHSUB(cx);
 		if (!is_xsub) {
 		    PADLIST * const padlist = CvPADLIST(cv);