Fix a memory leak in GC of font cache

* src/alloc.c (compact_font_cache_entry): Don't GC unmarked font
entities if some of the fonts it references are marked.  This
plugs a memory leak.  (Bug#21556)

1 files changed, 27 insertions, 3 deletions

diff --git a/src/alloc.c b/src/alloc.c
index 60751bcfe2b..81d644a16ad 100644
--- a/src/alloc.c
+++ b/src/alloc.c
@@ -5328,11 +5328,35 @@ compact_font_cache_entry (Lisp_Object entry)
              are not marked too.  But we must be sure that nothing is
              marked within OBJ before we really drop it.  */
           for (i = 0; i < size; i++)
-            if (VECTOR_MARKED_P (XFONT_ENTITY (AREF (XCDR (obj), i))))
-              break;
+            {
+              Lisp_Object objlist;
+
+              if (VECTOR_MARKED_P (XFONT_ENTITY (AREF (XCDR (obj), i))))
+                break;
+
+              objlist = AREF (AREF (XCDR (obj), i), FONT_OBJLIST_INDEX);
+              for (; CONSP (objlist); objlist = XCDR (objlist))
+                {
+                  Lisp_Object val = XCAR (objlist);
+                  struct font *font = XFONT_OBJECT (val);
+
+                  if (!NILP (AREF (val, FONT_TYPE_INDEX))
+                      && VECTOR_MARKED_P(font))
+                    break;
+                }
+              if (CONSP (objlist))
+                {
+                  /* Foiund a marked font, bail out.  */
+                  break;
+                }
+            }
 
           if (i == size)
-            drop = 1;
+            {
+              /* No marked fonts were found, so this entire font
+                 entity can be dropped.  */
+              drop = 1;
+            }
         }
       if (drop)
         *prev = XCDR (tail);