eval_intern.h: VAR_INITIALIZED

* eval_intern.h (VAR_INITIALIZED): macro to suppress
  maybe-uninitialized warnings by gcc 4.7 and 4.8.

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@45516 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

cont.c

@@ -510,6 +510,7 @@ cont_capture(volatile int *stat)
     if (ruby_setjmp(cont->jmpbuf)) {
 	volatile VALUE value;
 
+	VAR_INITIALIZED(cont);
 	value = cont->value;
 	if (cont->argc == -1) rb_exc_raise(value);
 	cont->value = Qnil;
@@ -1271,15 +1272,14 @@ rb_fiber_start(void)
 {
     rb_thread_t *th = GET_THREAD();
     rb_fiber_t *fib;
-    rb_context_t *cont;
     rb_proc_t *proc;
     int state;
 
     GetFiberPtr(th->fiber, fib);
-    cont = &fib->cont;
 
     TH_PUSH_TAG(th);
     if ((state = EXEC_TAG()) == 0) {
+	rb_context_t *cont = &VAR_FROM_MEMORY(fib)->cont;
 	int argc;
 	const VALUE *argv, args = cont->value;
 	GetProcPtr(cont->saved_thread.first_proc, proc);

eval_intern.h

@@ -128,6 +128,14 @@ extern int select_large_fdset(int, fd_set *, fd_set *, fd_set *, struct timeval
 #define PUSH_TAG() TH_PUSH_TAG(GET_THREAD())
 #define POP_TAG()      TH_POP_TAG()
 
+#if defined __GNUC__ && __GNUC__ == 4 && (__GNUC_MINOR__ == 7 || __GNUC_MINOR__ == 8)
+# define VAR_FROM_MEMORY(var) __extension__(*(__typeof__(var) volatile *)&(var))
+# define VAR_INITIALIZED(var) ((var) = VAR_FROM_MEMORY(var))
+#else
+# define VAR_FROM_MEMORY(var) (var)
+# define VAR_INITIALIZED(var) ((void)&(var))
+#endif
+
 /* clear th->state, and return the value */
 static inline int
 rb_threadptr_tag_state(rb_thread_t *th)
@@ -150,7 +158,7 @@ rb_threadptr_tag_jump(rb_thread_t *th, int st)
   [ISO/IEC 9899:1999] 7.13.1.1
 */
 #define TH_EXEC_TAG() \
-    (ruby_setjmp(_tag.buf) ? rb_threadptr_tag_state(_th) : (TH_REPUSH_TAG(), 0))
+    (ruby_setjmp(_tag.buf) ? rb_threadptr_tag_state(VAR_FROM_MEMORY(_th)) : (TH_REPUSH_TAG(), 0))
 
 #define EXEC_TAG() \
   TH_EXEC_TAG()

eval_jump.c

@@ -123,6 +123,7 @@ rb_exec_end_proc(void)
 	exec_end_procs_chain(&end_procs);
     }
     else {
+	VAR_INITIALIZED(th);
 	TH_TMPPOP_TAG();
 	error_handle(status);
 	if (!NIL_P(th->errinfo)) errinfo = th->errinfo;

proc.c

@@ -1899,6 +1899,7 @@ rb_method_call_with_block(int argc, VALUE *argv, VALUE method, VALUE pass_procva
 	}
 
 	th->passed_block = block;
+	VAR_INITIALIZED(data);
 	result = rb_vm_call(th, data->recv, data->id,  argc, argv, data->me, data->defined_class);
     }
     POP_TAG();

vm_eval.c

@@ -1060,6 +1060,8 @@ rb_iterate(VALUE (* it_proc) (VALUE), VALUE data1,
     TH_PUSH_TAG(th);
     state = TH_EXEC_TAG();
     if (state == 0) {
+	VAR_INITIALIZED(th);
+	VAR_INITIALIZED(node);
       iter_retry:
 	{
 	    rb_block_t *blockptr;