[Qemu-devel] [PATCH v9 08/37] qapi: Track all failures between visit_start/stop

[Eric Blake <eblake@redhat.com>]

Inside the generated code between visit_start_struct() and
visit_end_struct(), we were blindly setting the error into
the caller's errp parameter.  But a future patch to split
visit_end_struct() will require that we take action based
on whether an error has occurred, which requires us to track
all actions through a local err.  Rewrite the visits to be
more in line with the other generated calls.

Generated code changes look like:

|@@ -42,12 +42,18 @@ void visit_type_GuestAgentCommandInfo(Vi
|     Error *err = NULL;
|
|     visit_start_struct(v, (void **)obj, "GuestAgentCommandInfo", name, sizeof(GuestAgentCommandInfo), &err);
|-    if (!err) {
|-        if (*obj) {
|-            visit_type_GuestAgentCommandInfo_fields(v, obj, errp);
|-        }
|-        visit_end_struct(v, &err);
|+    if (err) {
|+        goto out;
|     }
|+    if (!*obj) {
|+        goto out_obj;
|+    }
|+    visit_type_GuestAgentCommandInfo_fields(v, obj, &err);
|+out_obj:
|+    error_propagate(errp, err);
|+    err = NULL;
|+    visit_end_struct(v, &err);
|+out:
|     error_propagate(errp, err);
| }

Signed-off-by: Eric Blake <eblake@redhat.com>
Reviewed-by: Marc-André Lureau <marcandre.lureau@redhat.com>

---
v9: enhance commit message
v8: no change
v7: place earlier in series
v6: based loosely on v5 7/46, but mostly a rewrite to get the last
generated code in the same form as all the others, so that the
later conversion to split visit_check_struct() will be easier
---
 scripts/qapi-visit.py | 16 +++++++++++-----
 1 file changed, 11 insertions(+), 5 deletions(-)

diff --git a/scripts/qapi-visit.py b/scripts/qapi-visit.py
index b93690b..4a4f67d 100644
--- a/scripts/qapi-visit.py
+++ b/scripts/qapi-visit.py
@@ -123,12 +123,18 @@ void visit_type_%(c_name)s(Visitor *v, %(c_name)s **obj, const char *name, Error
     Error *err = NULL;

     visit_start_struct(v, (void **)obj, "%(name)s", name, sizeof(%(c_name)s), &err);
-    if (!err) {
-        if (*obj) {
-            visit_type_%(c_name)s_fields(v, obj, errp);
-        }
-        visit_end_struct(v, &err);
+    if (err) {
+        goto out;
     }
+    if (!*obj) {
+        goto out_obj;
+    }
+    visit_type_%(c_name)s_fields(v, obj, &err);
+out_obj:
+    error_propagate(errp, err);
+    err = NULL;
+    visit_end_struct(v, &err);
+out:
     error_propagate(errp, err);
 }
 ''',
-- 
2.5.0