qapi: Reduce use of global variables in generators some

In preparation of the next commit, which will turn the generators into
modules.  These global variables will become local to main() then.

Signed-off-by: Markus Armbruster <armbru@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Reviewed-by: Marc-André Lureau <marcandre.lureau@redhat.com>
Message-Id: <20180211093607.27351-7-armbru@redhat.com>
Reviewed-by: Michael Roth <mdroth@linux.vnet.ibm.com>
Signed-off-by: Eric Blake <eblake@redhat.com>

scripts/qapi-commands.py

@@ -207,7 +207,7 @@ def gen_register_command(name, success_response):
     return ret
 
 
-def gen_registry(registry):
+def gen_registry(registry, prefix):
     ret = mcgen('''
 
 void %(c_prefix)sqmp_init_marshal(QmpCommandList *cmds)
@@ -224,7 +224,8 @@ void %(c_prefix)sqmp_init_marshal(QmpCommandList *cmds)
 
 
 class QAPISchemaGenCommandVisitor(QAPISchemaVisitor):
-    def __init__(self):
+    def __init__(self, prefix):
+        self._prefix = prefix
         self.decl = None
         self.defn = None
         self._regy = None
@@ -237,7 +238,7 @@ class QAPISchemaGenCommandVisitor(QAPISchemaVisitor):
         self._visited_ret_types = set()
 
     def visit_end(self):
-        self.defn += gen_registry(self._regy)
+        self.defn += gen_registry(self._regy, self._prefix)
         self._regy = None
         self._visited_ret_types = None
 
@@ -287,7 +288,7 @@ void %(c_prefix)sqmp_init_marshal(QmpCommandList *cmds);
                prefix=prefix, c_prefix=c_name(prefix, protect=False)))
 
 schema = QAPISchema(input_file)
-vis = QAPISchemaGenCommandVisitor()
+vis = QAPISchemaGenCommandVisitor(prefix)
 schema.visit(vis)
 genc.add(vis.defn)
 genh.add(vis.decl)