gc-hooks.patch

diff --git a/gc.c b/gc.c
index 6381eb1..487ee60 100644
--- a/source/gc.c
+++ b/source/gc.c
@@ -192,6 +192,76 @@ static void run_final();
 static VALUE nomem_error;
 static void garbage_collect();
 
+/* likely */
+#if __GNUC__ >= 3
+#define LIKELY(x)   (__builtin_expect((x), 1))
+#define UNLIKELY(x) (__builtin_expect((x), 0))
+#else /* __GNUC__ >= 3 */
+#define LIKELY(x)   (x)
+#define UNLIKELY(x) (x)
+#endif /* __GNUC__ >= 3 */
+
+typedef struct gc_event_hook {
+    rb_gc_event_hook_func_t func;
+    rb_gc_event_t events;
+    struct gc_event_hook *next;
+} rb_gc_event_hook_t;
+
+static rb_gc_event_hook_t *gc_event_hooks;
+
+#define EXEC_GC_EVENT_HOOK(event, obj) \
+    do { \
+	rb_gc_event_hook_t *hook = gc_event_hooks; \
+        rb_gc_event_hook_func_t hook_func; \
+        rb_gc_event_t events; \
+	\
+	while (hook) { \
+            hook_func = hook->func; \
+            events = hook->events; \
+            hook = hook->next; \
+	    if (events & event) \
+		(*hook_func)(event, obj); \
+	} \
+    } while (0)
+
+void
+rb_gc_add_event_hook(func, events)
+    rb_gc_event_hook_func_t func;
+    rb_gc_event_t events;
+{
+    rb_gc_event_hook_t *hook;
+
+    hook = ALLOC(rb_gc_event_hook_t);
+    hook->func = func;
+    hook->events = events;
+    hook->next = gc_event_hooks;
+    gc_event_hooks = hook;
+}
+
+int
+rb_gc_remove_event_hook(func)
+    rb_gc_event_hook_func_t func;
+{
+    rb_gc_event_hook_t *prev, *hook;
+
+    prev = NULL;
+    hook = gc_event_hooks;
+    while (hook) {
+	if (hook->func == func) {
+	    if (prev) {
+		prev->next = hook->next;
+	    }
+	    else {
+		gc_event_hooks = hook->next;
+	    }
+	    xfree(hook);
+	    return 0;
+	}
+	prev = hook;
+	hook = hook->next;
+    }
+    return -1;
+}
 
 NORETURN(void rb_exc_jump _((VALUE)));
 
@@ -1008,6 +1078,9 @@ rb_newobj()
 #endif
     live_objects++;
     allocated_objects++;
+    if (UNLIKELY(gc_event_hooks != NULL)) {
+      EXEC_GC_EVENT_HOOK(RUBY_GC_EVENT_NEWOBJ, obj);
+    }
     return obj;
 }
 
@@ -1893,6 +1966,9 @@ static int
 obj_free(obj)
     VALUE obj;
 {
+    if (UNLIKELY(gc_event_hooks != NULL)) {
+      EXEC_GC_EVENT_HOOK(RUBY_GC_EVENT_OBJFREE, obj);
+    }
     switch (BUILTIN_TYPE(obj)) {
       case T_NIL:
       case T_FIXNUM:
@@ -2191,6 +2267,9 @@ garbage_collect()
   /* This assumes that all registers are saved into the jmp_buf (and stack) */
   rb_setjmp(save_regs_gc_mark);
 
+  if (UNLIKELY(gc_event_hooks != NULL)) {
+    EXEC_GC_EVENT_HOOK(RUBY_GC_EVENT_START, Qnil);
+  }
 #if STACK_WIPE_SITES & 0x400
 # ifdef nativeAllocA
   if (__stack_past (top, stack_limit)) {
@@ -2211,6 +2290,9 @@ garbage_collect()
 #else
   garbage_collect_0(top);
 #endif
+  if (UNLIKELY(gc_event_hooks != NULL)) {
+    EXEC_GC_EVENT_HOOK(RUBY_GC_EVENT_END, Qnil);
+  }
 }
 
 void
diff --git a/node.h b/node.h
index 3e60603..af7a3fd 100644
--- a/source/node.h
+++ b/source/node.h
@@ -375,6 +375,19 @@ NODE *rb_copy_node_scope _((NODE *, NODE *));
 void rb_add_event_hook _((rb_event_hook_func_t,rb_event_t));
 int rb_remove_event_hook _((rb_event_hook_func_t));
 
+typedef unsigned int rb_gc_event_t;
+
+#define RUBY_GC_EVENT_NONE    0x00
+#define RUBY_GC_EVENT_START   0x01
+#define RUBY_GC_EVENT_END     0x02
+#define RUBY_GC_EVENT_NEWOBJ  0x04
+#define RUBY_GC_EVENT_OBJFREE 0x08
+#define RUBY_GC_EVENT_ALL     0xff
+
+typedef void (*rb_gc_event_hook_func_t) _((rb_gc_event_t,VALUE));
+void rb_gc_add_event_hook _((rb_gc_event_hook_func_t,rb_gc_event_t));
+int rb_gc_remove_event_hook _((rb_gc_event_hook_func_t));
+
 #if defined(HAVE_GETCONTEXT) && defined(HAVE_SETCONTEXT)
 #include <ucontext.h>
 #define USE_CONTEXT