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, 1 insertions, 3 deletions

diff --git a/sv.c b/sv.c
index ad2208e52c..d71a45d04c 100644
--- a/sv.c
+++ b/sv.c
@@ -13942,9 +13942,7 @@ Perl_cx_dup(pTHX_ PERL_CONTEXT *cxs, I32 ix, I32 max, CLONE_PARAMS* param)
 	    ncx->blk_oldcop = (COP*)any_dup(ncx->blk_oldcop, param->proto_perl);
 	    switch (CxTYPE(ncx)) {
 	    case CXt_SUB:
-		ncx->blk_sub.cv		= (ncx->blk_sub.olddepth == 0
-					   ? cv_dup_inc(ncx->blk_sub.cv, param)
-					   : cv_dup(ncx->blk_sub.cv,param));
+		ncx->blk_sub.cv		= cv_dup_inc(ncx->blk_sub.cv, param);
 		if(CxHASARGS(ncx)){
 		    ncx->blk_sub.argarray = av_dup_inc(ncx->blk_sub.argarray,param);
 		    ncx->blk_sub.savearray = av_dup_inc(ncx->blk_sub.savearray,param);