support interdependencies between utility code fragments

Cython/Compiler/Code.py

@@ -419,6 +419,9 @@ class GlobalState(object):
         """
         if name is None: name = id(utility_code)
         if self.check_utility_code_needed_and_register(name):
+            if utility_code.requires:
+                for dependency in utility_code.requires:
+                    self.use_utility_code(dependency)
             if utility_code.proto:
                 self.utilprotowriter.put(utility_code.proto)
             if utility_code.impl:

Cython/Utils.py

@@ -92,11 +92,12 @@ def long_literal(value):
 # a simple class that simplifies the usage of utility code
 
 class UtilityCode(object):
-    def __init__(self, proto=None, impl=None, init=None, cleanup=None):
+    def __init__(self, proto=None, impl=None, init=None, cleanup=None, requires=None):
         self.proto = proto
         self.impl = impl
         self.init = init
         self.cleanup = cleanup
+        self.requires = requires
 
     def write_init_code(self, writer, pos):
         if not self.init: