[Qemu-devel] [RFC PATCH v2 04/12] qapi-visit: Remove redundant functions for flat union base

[Eric Blake <eblake@redhat.com>]

The code for visiting the base class of a child struct created
visit_type_Base_fields(); the code for visiting the base class
of a flat union created visit_type_Union_fields(). If the same
type is shared between a struct and a union, the two functions
differed only by whether they visited the discriminator used by
the union. But if the base class always visits all its fields,
then we don't need to revisit the discriminator specially for
a union.  By consistently visiting the base class fields under
the name of the base class, we can eliminate some redundant
code.

Signed-off-by: Eric Blake <eblake@redhat.com>
---
 scripts/qapi-visit.py | 34 ++++++++++++++++++----------------
 1 file changed, 18 insertions(+), 16 deletions(-)

diff --git a/scripts/qapi-visit.py b/scripts/qapi-visit.py
index ef96345..b131c0d 100644
--- a/scripts/qapi-visit.py
+++ b/scripts/qapi-visit.py
@@ -115,7 +115,7 @@ if (err) {
 ''')

     pop_indent()
-    if re.search('^ *goto out;', ret, re.MULTILINE):
+    if base or members:
         ret += mcgen('''

 out:
@@ -241,8 +241,8 @@ def gen_visit_union(name, base, variants):
     ret = ''

     if base:
-        members = [m for m in base.members if m != variants.tag_member]
-        ret += gen_visit_struct_fields(name, None, members)
+        ret += gen_visit_struct_fields(base.name, base.base,
+                                       base.local_members)

     for var in variants.variants:
         # TODO ugly special case for simple union
@@ -263,29 +263,31 @@ void visit_type_%(c_name)s(Visitor *m, %(c_name)s **obj, const char *name, Error
 ''',
                  c_name=c_name(name), name=name)

-    if base:
-        ret += mcgen('''
-        visit_type_%(c_name)s_fields(m, obj, &err);
-        if (err) {
-            goto out_obj;
-        }
-''',
-                     c_name=c_name(name))
-
     tag_key = variants.tag_member.name
-    ret += mcgen('''
+    if base:
+        ret += mcgen('''
+        visit_type_%(c_name)s_fields(m, (%(c_name)s **)obj, &err);
+        if (err) {
+            goto out_obj;
+        }
+''',
+                     c_name=c_name(base.name))
+    else:
+        ret += mcgen('''
         visit_type_%(c_type)s(m, &(*obj)->%(c_name)s, "%(name)s", &err);
         if (err) {
             goto out_obj;
         }
+''',
+                     c_type=variants.tag_member.type.c_name(),
+                     c_name=c_name(tag_key), name=tag_key)
+    ret += mcgen('''
         if (!visit_start_union(m, !!(*obj)->data, &err) || err) {
             goto out_obj;
         }
         switch ((*obj)->%(c_name)s) {
 ''',
-                 c_type=variants.tag_member.type.c_name(),
-                 c_name=c_name(variants.tag_member.name),
-                 name=tag_key)
+                 c_name=c_name(tag_key))

     for var in variants.variants:
         # TODO ugly special case for simple union
-- 
2.4.3