From: Nicholas Clark <nick@ccl4.org>
Date: Sun, 1 Jul 2007 14:23:45 +0000 (+0000)
Subject: Avoid copying the AV in Perl_mro_get_linear_isa_dfs()
X-Git-Url: http://git.shadowcat.co.uk/gitweb/gitweb.cgi?a=commitdiff_plain;h=0fd7ece8441d209e64f8443de20b905a8a476805;p=p5sagit%2Fp5-mst-13.2.git

Avoid copying the AV in Perl_mro_get_linear_isa_dfs()

p4raw-id: //depot/perl@31513
---

diff --git a/mro.c b/mro.c
index 37573f1..c346570 100644
--- a/mro.c
+++ b/mro.c
@@ -87,7 +87,6 @@ AV*
 Perl_mro_get_linear_isa_dfs(pTHX_ HV *stash, I32 level)
 {
     AV* retval;
-    AV* tmp_retval; /* mortal to avoid leaks */
     GV** gvp;
     GV* gv;
     AV* av;
@@ -114,8 +113,8 @@ Perl_mro_get_linear_isa_dfs(pTHX_ HV *stash, I32 level)
 
     /* not in cache, make a new one */
 
-    tmp_retval = (AV*)sv_2mortal((SV*)newAV());
-    av_push(tmp_retval, newSVpv(stashname, 0)); /* add ourselves at the top */
+    retval = (AV*)sv_2mortal((SV *)newAV());
+    av_push(retval, newSVpv(stashname, 0)); /* add ourselves at the top */
 
     /* fetch our @ISA */
     gvp = (GV**)hv_fetchs(stash, "ISA", FALSE);
@@ -147,9 +146,7 @@ Perl_mro_get_linear_isa_dfs(pTHX_ HV *stash, I32 level)
             }
             else {
                 /* otherwise, recurse into ourselves for the MRO
-                   of this @ISA member, and append their MRO to ours.
-                   The recursive call could throw an exception, which
-                   has memory management implications here (tmp_retval) */
+                   of this @ISA member, and append their MRO to ours */
 		const AV *const subrv
 		    = mro_get_linear_isa_dfs(basestash, level + 1);
 
@@ -160,15 +157,17 @@ Perl_mro_get_linear_isa_dfs(pTHX_ HV *stash, I32 level)
 		SV *const subsv = *subrv_p++;
 		if(!hv_exists_ent(stored, subsv, 0)) {
 		    hv_store_ent(stored, subsv, &PL_sv_undef, 0);
-		    av_push(tmp_retval, newSVsv(subsv));
+		    av_push(retval, newSVsv(subsv));
 		}
             }
         }
     }
 
-    /* make the real retval out of tmp_retval, now that we're
-       past the exception dangers */
-    retval = av_make(AvFILLp(tmp_retval)+1, AvARRAY(tmp_retval));
+    /* now that we're past the exception dangers, grab our own reference to
+       the AV we're about to use for the result. The reference owned by the
+       mortals' stack will be released soon, so everything will balance.  */
+    SvREFCNT_inc_simple_void_NN(retval);
+    SvTEMP_off(retval);
 
     /* we don't want anyone modifying the cache entry but us,
        and we do so by replacing it completely */