From: Nicholas Clark <nick@ccl4.org>
Date: Fri, 22 Aug 2008 06:10:31 +0000 (+0000)
Subject: In S_mro_get_linear_isa_dfs(), hv_exists_ent() followed by an optional
X-Git-Url: http://git.shadowcat.co.uk/gitweb/gitweb.cgi?a=commitdiff_plain;h=8e45cc2bb9db96fb730868796fbfe1d0f7ece32d;p=p5sagit%2Fp5-mst-13.2.git

In S_mro_get_linear_isa_dfs(), hv_exists_ent() followed by an optional
hv_store_ent() can be replaced with an lvalue fetch.

p4raw-id: //depot/perl@34214
---

diff --git a/mro.c b/mro.c
index 13dd70a..a7ea282 100644
--- a/mro.c
+++ b/mro.c
@@ -185,9 +185,18 @@ S_mro_get_linear_isa_dfs(pTHX_ HV *stash, I32 level)
 	    }
 	    while(subrv_items--) {
 		SV *const subsv = *subrv_p++;
-		if(!hv_exists_ent(stored, subsv, 0)) {
-		    (void)hv_store_ent(stored, subsv, &PL_sv_undef, 0);
-		    av_push(retval, newSVsv(subsv));
+		/* LVALUE fetch will create a new undefined SV if necessary
+		 */
+		HE *const he = hv_fetch_ent(stored, subsv, 1, 0);
+		assert(he);
+		if(HeVAL(he) != &PL_sv_undef) {
+		    /* It was newly created.  Steal it for our new SV, and
+		       replace it in the hash with the "real" thing.  */
+		    SV *const val = HeVAL(he);
+
+		    HeVAL(he) = &PL_sv_undef;
+		    sv_setsv(val, subsv);
+		    av_push(retval, val);
 		}
             }
         }