offsetof(type, foo.bar) is (arguably) a GCCism

TL;DR see http://www.open-std.org/jtc1/sc22/wg14/www/docs/n2031.htm

Suppose we have:

struct X {
  struct Y {
    z_t z;
  } y;
} x;

then, you _cant_ infer offsetof(struct X, y.z). The ISO C99 section
7.17 says nothing about such situation. At least clang warns this
being an extension to the language (-Wextended-offsetof).

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@61560 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

1 files changed, 4 insertions, 2 deletions

diff --git a/thread_pthread.c b/thread_pthread.c
index 686c219ecb..469c9748b2 100644
--- a/thread_pthread.c
+++ b/thread_pthread.c
@@ -1221,11 +1221,13 @@ static void
 ubf_wakeup_all_threads(void)
 {
     rb_thread_t *th;
+    native_thread_data_t *dat;
 
     if (!ubf_threads_empty()) {
 	native_mutex_lock(&ubf_list_lock);
-	list_for_each(&ubf_list_head, th,
-		      native_thread_data.ubf_list) {
+	list_for_each(&ubf_list_head, dat, ubf_list) {
+	    th = (rb_thread_t *)(
+		((char *)dat) - offsetof(rb_thread_t, native_thread_data));
 	    ubf_wakeup_thread(th);
 	}
 	native_mutex_unlock(&ubf_list_lock);