Index: ChangeLog
===================================================================
RCS file: /mirrors/freedesktop/cairo/cairo/ChangeLog,v
retrieving revision 1.965
diff -u -p -r1.965 ChangeLog
--- ChangeLog	23 Aug 2005 19:48:17 -0000	1.965
+++ ChangeLog	23 Aug 2005 20:17:50 -0000
@@ -1,5 +1,19 @@
 2005-08-23  Carl Worth  <cworth@cworth.org>
 
+	* src/cairo-font.c: (cairo_font_face_reference),
+	(cairo_font_face_destroy), (cairo_scaled_font_reference),
+	(cairo_scaled_font_destroy):
+	* src/cairo-pattern.c: (cairo_pattern_reference),
+	(cairo_pattern_destroy):
+	* src/cairo-surface.c: (cairo_surface_reference),
+	(cairo_surface_destroy):
+	* src/cairo.c: (cairo_reference), (cairo_destroy):
+	Detect (by assert and crash) if users attempt to twice destroy or
+	re-reference a destroyed object. The condition for detecting this
+	case is a ref_count of 0.
+
+2005-08-23  Carl Worth  <cworth@cworth.org>
+
 	* CODING_STYLE: Revise the description of indentation and tabs to
 	be clear (I hope).
 
Index: src/cairo-font.c
===================================================================
RCS file: /mirrors/freedesktop/cairo/cairo/src/cairo-font.c,v
retrieving revision 1.73
diff -u -p -r1.73 cairo-font.c
--- src/cairo-font.c	23 Aug 2005 03:43:23 -0000	1.73
+++ src/cairo-font.c	23 Aug 2005 20:08:48 -0000
@@ -85,6 +85,8 @@ cairo_font_face_reference (cairo_font_fa
     if (font_face->ref_count == (unsigned int)-1)
 	return font_face;
 
+    assert (font_face->ref_count > 0);
+
     font_face->ref_count++;
 
     return font_face;
@@ -107,6 +109,8 @@ cairo_font_face_destroy (cairo_font_face
     if (font_face->ref_count == (unsigned int)-1)
 	return;
 
+    assert (font_face->ref_count > 0)
+
     if (--(font_face->ref_count) > 0)
 	return;
 
@@ -760,6 +764,8 @@ cairo_scaled_font_reference (cairo_scale
     if (scaled_font->ref_count == (unsigned int)-1)
 	return scaled_font;
 
+    assert (scaled_font->ref_count > 0);
+
     /* If the original reference count is 0, then this font must have
      * been found in font_map->holdovers, (which means this caching is
      * actually working). So now we remove it from the holdovers
@@ -807,6 +813,8 @@ cairo_scaled_font_destroy (cairo_scaled_
     if (scaled_font->ref_count == (unsigned int)-1)
 	return;
 
+    assert (scaled_font->ref_count > 0);
+
     if (--(scaled_font->ref_count) > 0)
 	return;
 
Index: src/cairo-pattern.c
===================================================================
RCS file: /mirrors/freedesktop/cairo/cairo/src/cairo-pattern.c,v
retrieving revision 1.61
diff -u -p -r1.61 cairo-pattern.c
--- src/cairo-pattern.c	23 Aug 2005 03:43:23 -0000	1.61
+++ src/cairo-pattern.c	23 Aug 2005 20:14:22 -0000
@@ -532,6 +532,8 @@ cairo_pattern_reference (cairo_pattern_t
     if (pattern->ref_count == (unsigned int)-1)
 	return pattern;
 
+    assert (pattern->ref_count > 0);
+
     pattern->ref_count++;
 
     return pattern;
@@ -570,6 +572,8 @@ cairo_pattern_destroy (cairo_pattern_t *
     if (pattern->ref_count == (unsigned int)-1)
 	return;
 
+    assert (pattern->ref_count > 0);
+
     pattern->ref_count--;
     if (pattern->ref_count)
 	return;
Index: src/cairo-surface.c
===================================================================
RCS file: /mirrors/freedesktop/cairo/cairo/src/cairo-surface.c,v
retrieving revision 1.97
diff -u -p -r1.97 cairo-surface.c
--- src/cairo-surface.c	21 Aug 2005 19:13:17 -0000	1.97
+++ src/cairo-surface.c	23 Aug 2005 20:14:56 -0000
@@ -268,6 +268,8 @@ cairo_surface_reference (cairo_surface_t
     if (surface->ref_count == (unsigned int)-1)
 	return surface;
 
+    assert (surface->ref_count > 0);
+
     surface->ref_count++;
 
     return surface;
@@ -290,6 +292,8 @@ cairo_surface_destroy (cairo_surface_t *
     if (surface->ref_count == (unsigned int)-1)
 	return;
 
+    assert (surface->ref_count > 0);
+
     surface->ref_count--;
     if (surface->ref_count)
 	return;
Index: src/cairo.c
===================================================================
RCS file: /mirrors/freedesktop/cairo/cairo/src/cairo.c,v
retrieving revision 1.130
diff -u -p -r1.130 cairo.c
--- src/cairo.c	23 Aug 2005 07:03:10 -0000	1.130
+++ src/cairo.c	23 Aug 2005 20:15:37 -0000
@@ -222,6 +222,8 @@ cairo_reference (cairo_t *cr)
 {
     if (cr->ref_count == (unsigned int)-1)
 	return cr;
+
+    assert (cr->ref_count > 0);
     
     cr->ref_count++;
 
@@ -241,6 +243,8 @@ cairo_destroy (cairo_t *cr)
 {
     if (cr->ref_count == (unsigned int)-1)
 	return;
+
+    assert (cr->ref_count > 0);
     
     cr->ref_count--;
     if (cr->ref_count)