Resolve misc warnings in clang

Author: yugui

ext/jsonnet/callbacks.c

@@ -27,7 +27,7 @@ invoke_callback(VALUE args)
 {
     long len = RARRAY_LEN(args);
     VALUE callback = rb_ary_entry(args, 0);
-    return rb_funcall2(callback, id_call, len - 1, RARRAY_PTR(args) + 1);
+    return rb_funcall2(callback, id_call, (int)(len - 1), RARRAY_PTR(args) + 1);
 }
 
 /*

ext/jsonnet/vm.c

@@ -7,6 +7,10 @@
 
 #include "ruby_jsonnet.h"
 
+#ifndef NORETURN
+# define NORETURN(x) x
+#endif
+
 /*
  * defines the core part of Jsonnet::VM
  */
@@ -424,7 +428,7 @@ rubyjsonnet_init_vm(VALUE mJsonnet)
 }
 
 static void
-raise_error(VALUE exception_class, struct JsonnetVm *vm, char *msg, rb_encoding *enc)
+NORETURN(raise_error)(VALUE exception_class, struct JsonnetVm *vm, char *msg, rb_encoding *enc)
 {
     VALUE ex;
     const int state = rubyjsonnet_jump_tag(msg);
@@ -451,13 +455,13 @@ raise_error(VALUE exception_class, struct JsonnetVm *vm, char *msg, rb_encoding
  * @sa rescue_callback
  */
 static void
-raise_eval_error(struct JsonnetVm *vm, char *msg, rb_encoding *enc)
+NORETURN(raise_eval_error)(struct JsonnetVm *vm, char *msg, rb_encoding *enc)
 {
     raise_error(eEvaluationError, vm, msg, enc);
 }
 
 static void
-raise_format_error(struct JsonnetVm *vm, char *msg, rb_encoding *enc)
+NORETURN(raise_format_error)(struct JsonnetVm *vm, char *msg, rb_encoding *enc)
 {
     raise_error(eFormatError, vm, msg, enc);
 }