diff --git a/cameo/cameo.c b/cameo/cameo.c
index 93250e5..f575555 100644
--- a/cameo/cameo.c
+++ b/cameo/cameo.c
@@ -1,8 +1,8 @@
 /*
  * cameo.c - Toolpath adaptation and machine control
  *
- * Written 2010 by Werner Almesberger
- * Copyright 2010 Werner Almesberger
+ * Written 2010-2011 by Werner Almesberger
+ * Copyright 2010-2011 Werner Almesberger
  *
  * This program is free software; you can redistribute it and/or modify
  * it under the terms of the GNU General Public License as published by
@@ -100,7 +100,7 @@ int main(int argc, char **argv)
 		paths = gerber_read(in, r);
 	else
 		paths = gnuplot_read(in, r);
-	tool_comp_paths(paths, dog_bone, 0);
+	paths = tool_comp_paths(paths, dog_bone, 0); /* @@@ memory leak */
 	gnuplot_write(out, paths);
 
 	return 0;
diff --git a/cameo/lang.y b/cameo/lang.y
index 48bdd7c..2806b6c 100644
--- a/cameo/lang.y
+++ b/cameo/lang.y
@@ -243,8 +243,12 @@ command:
 		}
 	| TOK_OFFSET offset_options
 		{
-			tool_comp_paths(paths,
+			struct path *new;
+
+			new = tool_comp_paths(paths,
 			    !!($2 & OO_DOG), !!($2 & OO_INSIDE));
+			clear_paths();
+			paths = new;
 		}
 	| TOK_OPTIMIZE
 		{
diff --git a/cameo/ops.c b/cameo/ops.c
index 3d86df2..a90599f 100644
--- a/cameo/ops.c
+++ b/cameo/ops.c
@@ -19,23 +19,24 @@
 #include "ops.h"
 
 
-static void tool_comp_1(struct path *path, int inside, int dog_bone)
+static struct path *tool_comp_1(const struct path *path, int inside,
+    int dog_bone)
 {
 	int left;
-	struct path *new;
 
 	left = path_tool_is_left(path);
 	if (inside)
-		new = path_offset(path, !left, path->notch);
+		return path_offset(path, !left, path->notch);
 	else
-		new = path_offset(path, left, path->notch || dog_bone);
-	path_replace(path, new);
+		return path_offset(path, left, path->notch || dog_bone);
 }
 
 
-void tool_comp_paths(struct path *paths, int dog_bone, int all_inside)
+struct path *tool_comp_paths(const struct path *paths, int dog_bone,
+    int all_inside)
 {
-	struct path *leftmost, *path;
+	const struct path *leftmost, *path;
+	struct path *new = NULL, **anchor = &new;
 
 	/*
 	 * We don't have an algorithm (yet) that can detect which paths are
@@ -50,13 +51,18 @@ void tool_comp_paths(struct path *paths, int dog_bone, int all_inside)
 
 	leftmost = path_find_leftmost(paths);
 	for (path = paths; path; path = path->next)
-		if (path != leftmost && (all_inside || !path->outside))
-			tool_comp_1(path, 1, dog_bone);
+		if (path != leftmost && (all_inside || !path->outside)) {
+			*anchor = tool_comp_1(path, 1, dog_bone);
+			anchor = &(*anchor)->next;
+		}
 	if (!all_inside)
 		for (path = paths; path; path = path->next)
-			if (path != leftmost && path->outside)
-				tool_comp_1(path, 0, dog_bone);
-	tool_comp_1(leftmost, all_inside, dog_bone);
+			if (path != leftmost && path->outside) {
+				*anchor = tool_comp_1(path, 0, dog_bone);
+				anchor = &(*anchor)->next;
+			}
+	*anchor = tool_comp_1(leftmost, all_inside, dog_bone);
+	return new;
 }
 
 
diff --git a/cameo/ops.h b/cameo/ops.h
index 52fff4d..4e8d9fb 100644
--- a/cameo/ops.h
+++ b/cameo/ops.h
@@ -17,7 +17,8 @@
 #include "path.h"
 
 
-void tool_comp_paths(struct path *paths, int dog_bone, int all_inside);
+struct path *tool_comp_paths(const struct path *paths, int dog_bone,
+    int all_inside);
 struct path *try_drill(struct path *path, double d_min, double d_max);
 struct path *try_mill(struct path *path, double diam, double step, int any);
 struct path *optimize_paths(struct path *paths);
diff --git a/cameo/path.c b/cameo/path.c
index 6732e29..2abd18d 100644
--- a/cameo/path.c
+++ b/cameo/path.c
@@ -134,18 +134,6 @@ void path_add(struct path *path, double x, double y, double z)
 }
 
 
-void path_replace(struct path *old, struct path *new)
-{
-	struct path *next = old->next;
-
-	free_points(old->first);
-	free((void *) old->id);
-	*old = *new;
-	old->next = next;
-	free(new);
-}
-
-
 struct path *path_reverse(const struct path *path)
 {
 	struct path *new;
@@ -348,10 +336,10 @@ struct path *path_offset(const struct path *path, int left, int notch)
 }
 
 
-struct path *path_find_leftmost(struct path *path)
+const struct path *path_find_leftmost(const struct path *path)
 {
 	const struct point *p;
-	struct path *best = NULL;
+	const struct path *best = NULL;
 	double best_x = HUGE_VAL;
 
 	while (path) {
diff --git a/cameo/path.h b/cameo/path.h
index a25a4fc..d419a46 100644
--- a/cameo/path.h
+++ b/cameo/path.h
@@ -32,11 +32,10 @@ struct path {
 
 struct path *path_new(double r_tool, const char *id);
 void path_add(struct path *path, double x, double y, double z);
-void path_replace(struct path *old, struct path *new);
 struct path *path_reverse(const struct path *path);
 int path_tool_is_left(const struct path *path);
 struct path *path_offset(const struct path *path, int left, int notch);
-struct path *path_find_leftmost(struct path *path);
+const struct path *path_find_leftmost(const struct path *path);
 void path_free(struct path *path);
 struct path *path_connect(struct path *path);
 void path_stats(const struct path *path);