From: Tassilo von Parseval <tassilo.parseval@post.rwth-aachen.de>
Date: Tue, 24 Feb 2004 12:02:57 +0000 (+0100)
Subject: optimization for map in scalar context
X-Git-Url: http://git.shadowcat.co.uk/gitweb/gitweb.cgi?a=commitdiff_plain;h=22023b2636bf15292e047d7ecd514d472b7abffc;p=p5sagit%2Fp5-mst-13.2.git

optimization for map in scalar context
Message-id: <20040224110257.GA5510@ethan>

p4raw-id: //depot/perl@22369
---

diff --git a/pp_ctl.c b/pp_ctl.c
index e91ff54..26fb164 100644
--- a/pp_ctl.c
+++ b/pp_ctl.c
@@ -939,8 +939,19 @@ PP(pp_mapwhile)
 	}
 	/* copy the new items down to the destination list */
 	dst = PL_stack_base + (PL_markstack_ptr[-2] += items) - 1;
-	while (items-- > 0)
-	    *dst-- = SvTEMP(TOPs) ? POPs : sv_mortalcopy(POPs);
+	if (gimme == G_ARRAY) {
+	    while (items-- > 0)
+		*dst-- = SvTEMP(TOPs) ? POPs : sv_mortalcopy(POPs);
+	}
+	else { 
+	    /* scalar context: we don't care about which values map returns
+	     * (we use undef here). And so we certainly don't want to do mortal
+	     * copies of meaningless values. */
+	    while (items-- > 0) {
+		POPs;
+		*dst-- = &PL_sv_undef;
+	    }
+	}
     }
     LEAVE;					/* exit inner scope */