# HG changeset patch
# User Paul Boddie <paul@boddie.org.uk>
# Date 1479415706 -3600
# Node ID 653ac525f897a52afbd098619a4938d5558eb06c
# Parent  e9b03527f13204f1b086102f1a39bfeffbf24e95
Record module relationships involving non-static objects in order to detect
problematic module interdependencies, also generating a module initialisation
sequence from the more general relationships already defined.

diff -r e9b03527f132 -r 653ac525f897 generator.py
--- a/generator.py	Thu Nov 17 21:45:25 2016 +0100
+++ b/generator.py	Thu Nov 17 21:48:26 2016 +0100
@@ -910,19 +910,17 @@
     __Try
     {"""
 
-        for name in self.importer.modules.keys():
+        for name in self.importer.order_modules():
             function_name = "__main_%s" % encode_path(name)
             print >>f_signatures, "void %s();" % function_name
 
-            # Emit the main module's function last.
             # Omit the native module.
 
-            if name not in ("__main__", "native"):
+            if name != "native":
                 print >>f_code, """\
         %s();""" % function_name
 
         print >>f_code, """\
-        __main___main__();
         return 0;
     }
     __Catch_anonymous
diff -r e9b03527f132 -r 653ac525f897 importer.py
--- a/importer.py	Thu Nov 17 21:45:25 2016 +0100
+++ b/importer.py	Thu Nov 17 21:48:26 2016 +0100
@@ -397,6 +397,7 @@
         "Resolve dependencies between modules."
 
         self.waiting = {}
+        self.depends = {}
 
         for module in self.modules.values():
 
@@ -418,7 +419,11 @@
                     provider = self.get_module_provider(found.unresolved() and ref or found)
                     ref.mutate(found)
 
-                    if provider:
+                    # Record any external dependency.
+
+                    if provider and provider != module.name:
+
+                        # Record the provider dependency.
 
                         module.required.add(provider)
                         self.accessing_modules[provider].add(module.name)
@@ -437,6 +442,12 @@
                             if self.verbose:
                                 print >>sys.stderr, "Requiring", provider, "for", ref
 
+                        # Record a module ordering dependency.
+
+                        if not found.static():
+                            init_item(self.depends, module.name, set)
+                            self.depends[module.name].add(provider)
+
         # Check modules again to see if they are now required and should now
         # cause the inclusion of other modules providing objects to the program.
 
@@ -458,6 +469,43 @@
                         print >>sys.stderr, "Requiring", provider
                     self.require_providers(provider)
 
+    def order_modules(self):
+
+        "Produce a module initialisation ordering."
+
+        self.check_ordering()
+        return self.order_modules_for_module("__main__", set())
+
+    def order_modules_for_module(self, module_name, visited):
+
+        """
+        Order the modules required by 'module_name', using 'visited' to track
+        visited modules.
+        """
+
+        if module_name in visited:
+            return []
+
+        module = self.modules[module_name]
+        visited.add(module_name)
+        ordered = [module_name]
+
+        for module_name in module.required:
+            modules = self.order_modules_for_module(module_name, visited)
+            ordered[:0] = modules
+            visited.update(modules)
+
+        return ordered
+
+    def check_ordering(self):
+
+        "Check the ordering dependencies."
+
+        for module_name, modules in self.depends.items():
+            for provider in modules:
+                if self.depends.has_key(provider) and module_name in self.depends[provider]:
+                    raise ProgramError, "Modules %s and %s may not depend on each other for non-static objects." % (module_name, provider)
+
     def find_dependency(self, ref):
 
         "Find the ultimate dependency for 'ref'."
diff -r e9b03527f132 -r 653ac525f897 lib/__builtins__/io.py
--- a/lib/__builtins__/io.py	Thu Nov 17 21:45:25 2016 +0100
+++ b/lib/__builtins__/io.py	Thu Nov 17 21:48:26 2016 +0100
@@ -61,9 +61,9 @@
     'nl' is given as a true value.
     """
 
-    # Import locally to ensure that the object is initialised.
-    # Otherwise, if imported at the module level, the sys module may not have
-    # been set up.
+    # If imported at the module level, the sys module must be set up first,
+    # which should be ensured by the module ordering activity, and a module
+    # attribute will be employed to hold a reference to sys.stdout.
 
     from sys import stdout