qapi/commands: add #if conditions to commands

Wrap generated code with #if/#endif using an 'ifcontext' on
QAPIGenCSnippet objects.
Signed-off-by: NMarc-André Lureau <marcandre.lureau@redhat.com>
Message-Id: <20180703155648.11933-10-marcandre.lureau@redhat.com>
Reviewed-by: NMarkus Armbruster <armbru@redhat.com>
[Line breaks tweaked]
Signed-off-by: NMarkus Armbruster <armbru@redhat.com>

scripts/qapi/commands.py

@@ -239,7 +239,7 @@ class QAPISchemaGenCommandVisitor(QAPISchemaModularCVisitor):
         QAPISchemaModularCVisitor.__init__(
             self, prefix, 'qapi-commands',
             ' * Schema-defined QAPI/QMP commands', __doc__)
-        self._regy = ''
+        self._regy = QAPIGenCCode()
         self._visited_ret_types = {}
 
     def _begin_module(self, name):
@@ -275,20 +275,28 @@ class QAPISchemaGenCommandVisitor(QAPISchemaModularCVisitor):
 void %(c_prefix)sqmp_init_marshal(QmpCommandList *cmds);
 ''',
                        c_prefix=c_name(self._prefix, protect=False)))
-        genc.add(gen_registry(self._regy, self._prefix))
+        genc.add(gen_registry(self._regy.get_content(), self._prefix))
 
     def visit_command(self, name, info, ifcond, arg_type, ret_type, gen,
                       success_response, boxed, allow_oob, allow_preconfig):
         if not gen:
             return
-        self._genh.add(gen_command_decl(name, arg_type, boxed, ret_type))
+        # FIXME: If T is a user-defined type, the user is responsible
+        # for making this work, i.e. to make T's condition the
+        # conjunction of the T-returning commands' conditions.  If T
+        # is a built-in type, this isn't possible: the
+        # qmp_marshal_output_T() will be generated unconditionally.
         if ret_type and ret_type not in self._visited_ret_types[self._genc]:
             self._visited_ret_types[self._genc].add(ret_type)
-            self._genc.add(gen_marshal_output(ret_type))
-        self._genh.add(gen_marshal_decl(name))
-        self._genc.add(gen_marshal(name, arg_type, boxed, ret_type))
-        self._regy += gen_register_command(name, success_response, allow_oob,
-                                           allow_preconfig)
+            with ifcontext(ret_type.ifcond,
+                           self._genh, self._genc, self._regy):
+                self._genc.add(gen_marshal_output(ret_type))
+        with ifcontext(ifcond, self._genh, self._genc, self._regy):
+            self._genh.add(gen_command_decl(name, arg_type, boxed, ret_type))
+            self._genh.add(gen_marshal_decl(name))
+            self._genc.add(gen_marshal(name, arg_type, boxed, ret_type))
+            self._regy.add(gen_register_command(name, success_response,
+                                                allow_oob, allow_preconfig))
 
 
 def gen_commands(schema, output_dir, prefix):

tests/test-qmp-cmds.c

@@ -12,12 +12,12 @@
 
 static QmpCommandList qmp_commands;
 
-/* #if defined(TEST_IF_STRUCT) && defined(TEST_IF_CMD) */
+#if defined(TEST_IF_STRUCT) && defined(TEST_IF_CMD)
 UserDefThree *qmp_TestIfCmd(TestIfStruct *foo, Error **errp)
 {
     return NULL;
 }
-/* #endif */
+#endif
 
 UserDefThree *qmp_TestCmdReturnDefThree(Error **errp)
 {