Bug 1043144 - Don't write machc bytecode file; r=mshal

When writing bytecode, Python will append "c" to the loaded filename to
produce a bytecode file. Since "mach" was being imported, this resulted
in the creation of a "machc" file.

The implementation of imp.load_module() in CPython's import.c checks
sys.dont_write_bytecode. So, we wrap imp.load_module to set this flag
when importing mach.

--HG--
extra : rebase_source : 248a2349663affee3920a0726e10818d57c6ff17
extra : amend_source : 221280da9963cf91975658144ff3011353852fee

mach

@@ -92,6 +92,7 @@ if __name__ == '__main__':
         def fork_interpose():
             import imp
             import os
+            import sys
             orig_find_module = imp.find_module
             def my_find_module(name, dirs):
                 if name == 'mach':
@@ -100,7 +101,23 @@ if __name__ == '__main__':
                     return (f, path, ('', 'r', imp.PY_SOURCE))
                 return orig_find_module(name, dirs)
 
+            # Don't allow writing bytecode file for mach module.
+            orig_load_module = imp.load_module
+            def my_load_module(name, file, path, description):
+                # multiprocess.forking invokes imp.load_module manually and
+                # hard-codes the name __parents_main__ as the module name.
+                if name == '__parents_main__':
+                    old_bytecode = sys.dont_write_bytecode
+                    sys.dont_write_bytecode = True
+                    try:
+                        return orig_load_module(name, file, path, description)
+                    finally:
+                        sys.dont_write_bytecode = old_bytecode
+
+                return orig_load_module(name, file, path, description)
+
             imp.find_module = my_find_module
+            imp.load_module = my_load_module
             from multiprocessing.forking import main; main()
 
         def my_get_command_line():