From: Jan Nieuwenhuizen <janneke@gnu.org>
Date: Sun, 30 Jun 2002 15:17:12 +0000 (+0000)
Subject: (mark_smob): don't mark parents, explain why.
X-Git-Tag: release/1.5.64~2
X-Git-Url: https://git.donarmstrong.com/?a=commitdiff_plain;h=4a9cacbac6985b76ab22a683ecb0cafc1491e3e0;p=lilypond.git

(mark_smob): don't mark parents, explain why.
---

diff --git a/ChangeLog b/ChangeLog
index ba51941fb6..2c70e2ce7b 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,5 +1,7 @@
 2002-06-30  Jan Nieuwenhuizen  <janneke@gnu.org>
 
+	* lily/grob.cc (mark_smob): don't mark parents, explain why.
+
 	* tex/lilyponddefs.tex: Define outputscale only once.
 
 2002-06-29  Jan Nieuwenhuizen  <janneke@gnu.org>
@@ -68,7 +70,7 @@
 	lists of grobs. This should fix the problems of lily in
 	combination with pthreads/qthreads.
 
-	* lily/grob.cc (mark_smob): bugfix: mark X parent too.
+	* lily/grob.cc (mark_smob): bugfix: mark other parent too.
 
 2002-06-23  Chris Jackson  <chris@fluffhouse.org.uk>
 
diff --git a/lily/break-substitution.cc b/lily/break-substitution.cc
index 73c24c20e5..4f560e85cd 100644
--- a/lily/break-substitution.cc
+++ b/lily/break-substitution.cc
@@ -44,6 +44,15 @@ substitute_grob (Grob *sc)
       if (!line)
 	return sc->self_scm();
 
+      /*
+	We don't return SCM_UNDEFINED for
+	suicided grobs, for two reasons
+
+	- it doesn't work (strange disappearing objects)
+
+	- it forces us to mark the parents of a grob, leading to
+	a huge recursion in the GC routine.
+       */
 
       /*
 	This was introduced in 1.3.49 as a measure to prevent
diff --git a/lily/grob.cc b/lily/grob.cc
index 992c4c9e34..c39d0125bd 100644
--- a/lily/grob.cc
+++ b/lily/grob.cc
@@ -762,9 +762,15 @@ Grob::mark_smob (SCM ses)
     {
       scm_gc_mark (s->dim_cache_[a].offset_callbacks_);
       scm_gc_mark (s->dim_cache_[a].dimension_);
-      Grob *p = s->get_parent (Axis (a));
-      if (p)
-	scm_gc_mark (p->self_scm ());
+      
+      /*
+	don't mark the parents. The pointers in the mutable property
+	list form two tree like structures (one for X relations, one
+	for Y relations). Marking these can be done in limited stack
+	space.  If we add the parents, we will jump between X and Y in
+	an erratic manner, leading to much more recursion depth (and
+	core dumps if we link to pthreads.
+       */
     }
   
   if (s->original_l_)