Fix for unbounded memory growth problem reproduced with GCC 4.4.1

on 32 bit x86 Fedora. This happens because the lazy list variable
``data'' in the match_files function is optimized to a register,
but a stale value of that variable persists in the backing storage.

1 files changed, 17 insertions, 0 deletions

diff --git a/gc.c b/gc.c
index 2a659e2b..284ca711 100644
--- a/gc.c
+++ b/gc.c
@@ -486,3 +486,20 @@ void unmark(void)
     }
   }
 }
+
+/*
+ * This function does nothing.
+ * gc_hint(x) just takes the address of local variable x
+ * and passes it to this function. This prevents the compiler
+ * from caching the value across function calls.
+ * This is needed for situations where
+ * - a compiler caches a variable in a register, but not entirely (the variable
+ *   has a backing memory location); and 
+ * - that location contains a stale old value of the variable, which cannot be
+ *   garbage-collected as a result; and
+ * - this causes a problem, like unbounded memory growth.
+ */
+void gc_hint_func(val *val)
+{
+  (void) val;
+}