1 files changed, 21 insertions, 12 deletions
diff --git a/thread.c b/thread.c
index 33cbe9f051..85ed88cadc 100644
--- a/thread.c
+++ b/thread.c
@@ -3723,18 +3723,27 @@ thread_shield_alloc(VALUE klass)
 #define THREAD_SHIELD_WAITING_MASK (FL_USER0|FL_USER1|FL_USER2|FL_USER3|FL_USER4|FL_USER5|FL_USER6|FL_USER7|FL_USER8|FL_USER9|FL_USER10|FL_USER11|FL_USER12|FL_USER13|FL_USER14|FL_USER15|FL_USER16|FL_USER17|FL_USER18|FL_USER19)
 #define THREAD_SHIELD_WAITING_SHIFT (FL_USHIFT)
 #define rb_thread_shield_waiting(b) (int)((RBASIC(b)->flags&THREAD_SHIELD_WAITING_MASK)>>THREAD_SHIELD_WAITING_SHIFT)
-#define rb_thread_shield_waiting_inc(b) do { \
-    int w = rb_thread_shield_waiting(b); \
-    w++; \
-    RBASIC(b)->flags &= ~THREAD_SHIELD_WAITING_MASK; \
-    RBASIC(b)->flags |= ((VALUE)w << THREAD_SHIELD_WAITING_SHIFT);	\
-} while (0)
-#define rb_thread_shield_waiting_dec(b) do { \
-    int w = rb_thread_shield_waiting(b); \
-    w--; \
-    RBASIC(b)->flags &= ~THREAD_SHIELD_WAITING_MASK; \
-    RBASIC(b)->flags |= ((VALUE)w << THREAD_SHIELD_WAITING_SHIFT); \
-} while (0)
+
+static inline void
+rb_thread_shield_waiting_inc(VALUE b)
+{
+    int w = rb_thread_shield_waiting(b);
+    w++;
+    if (w > (THREAD_SHIELD_WAITING_MASK>>THREAD_SHIELD_WAITING_SHIFT))
+	rb_raise(rb_eRuntimeError, "waiting count overflow");
+    RBASIC(b)->flags &= ~THREAD_SHIELD_WAITING_MASK;
+    RBASIC(b)->flags |= ((VALUE)w << THREAD_SHIELD_WAITING_SHIFT);
+}
+
+static inline void
+rb_thread_shield_waiting_dec(VALUE b)
+{
+    int w = rb_thread_shield_waiting(b);
+    if (!w) rb_raise(rb_eRuntimeError, "waiting count underflow");
+    w--;
+    RBASIC(b)->flags &= ~THREAD_SHIELD_WAITING_MASK;
+    RBASIC(b)->flags |= ((VALUE)w << THREAD_SHIELD_WAITING_SHIFT);
+}
 
 VALUE
 rb_thread_shield_new(void)