qapi: Drop unused error argument for list and implicit struct

No backend was setting an error when ending the visit of a list or
implicit struct, or when moving to the next list node.  Make the
callers a bit easier to follow by making this a part of the contract,
and removing the errp argument - callers can then unconditionally end
an object as part of cleanup without having to think about whether a
second error is dominated by a first, because there is no second
error.

A later patch will then tackle the larger task of splitting
visit_end_struct(), which can indeed set an error.

Signed-off-by: Eric Blake <eblake@redhat.com>
Message-Id: <1454075341-13658-24-git-send-email-eblake@redhat.com>
Signed-off-by: Markus Armbruster <armbru@redhat.com>

hw/ppc/spapr_drc.c

@@ -315,11 +315,7 @@ static void prop_get_fdt(Object *obj, Visitor *v, const char *name,
                     return;
                 }
             }
-            visit_end_list(v, &err);
-            if (err) {
-                error_propagate(errp, err);
-                return;
-            }
+            visit_end_list(v);
             break;
         }
         default:

include/qapi/visitor-impl.h

@@ -24,11 +24,14 @@ struct Visitor
 
     void (*start_implicit_struct)(Visitor *v, void **obj, size_t size,
                                   Error **errp);
-    void (*end_implicit_struct)(Visitor *v, Error **errp);
+    /* May be NULL */
+    void (*end_implicit_struct)(Visitor *v);
 
     void (*start_list)(Visitor *v, const char *name, Error **errp);
-    GenericList *(*next_list)(Visitor *v, GenericList **list, Error **errp);
-    void (*end_list)(Visitor *v, Error **errp);
+    /* Must be set */
+    GenericList *(*next_list)(Visitor *v, GenericList **list);
+    /* Must be set */
+    void (*end_list)(Visitor *v);
 
     void (*type_enum)(Visitor *v, const char *name, int *obj,
                       const char *const strings[], Error **errp);

include/qapi/visitor.h

@@ -1,6 +1,7 @@
 /*
  * Core Definitions for QAPI Visitor Classes
  *
+ * Copyright (C) 2012-2016 Red Hat, Inc.
  * Copyright IBM, Corp. 2011
  *
  * Authors:
@@ -32,10 +33,11 @@ void visit_start_struct(Visitor *v, const char *name, void **obj,
 void visit_end_struct(Visitor *v, Error **errp);
 void visit_start_implicit_struct(Visitor *v, void **obj, size_t size,
                                  Error **errp);
-void visit_end_implicit_struct(Visitor *v, Error **errp);
+void visit_end_implicit_struct(Visitor *v);
+
 void visit_start_list(Visitor *v, const char *name, Error **errp);
-GenericList *visit_next_list(Visitor *v, GenericList **list, Error **errp);
-void visit_end_list(Visitor *v, Error **errp);
+GenericList *visit_next_list(Visitor *v, GenericList **list);
+void visit_end_list(Visitor *v);
 
 /**
  * Check if an optional member @name of an object needs visiting.

qapi/opts-visitor.c

@@ -1,7 +1,7 @@
 /*
  * Options Visitor
  *
- * Copyright Red Hat, Inc. 2012, 2013
+ * Copyright Red Hat, Inc. 2012-2016
  *
  * Author: Laszlo Ersek <lersek@redhat.com>
  *
@@ -221,7 +221,7 @@ opts_start_list(Visitor *v, const char *name, Error **errp)
 
 
 static GenericList *
-opts_next_list(Visitor *v, GenericList **list, Error **errp)
+opts_next_list(Visitor *v, GenericList **list)
 {
     OptsVisitor *ov = to_ov(v);
     GenericList **link;
@@ -270,7 +270,7 @@ opts_next_list(Visitor *v, GenericList **list, Error **errp)
 
 
 static void
-opts_end_list(Visitor *v, Error **errp)
+opts_end_list(Visitor *v)
 {
     OptsVisitor *ov = to_ov(v);
 

qapi/qapi-dealloc-visitor.c

@@ -1,6 +1,7 @@
 /*
  * Dealloc Visitor
  *
+ * Copyright (C) 2012-2016 Red Hat, Inc.
  * Copyright IBM, Corp. 2011
  *
  * Authors:
@@ -84,7 +85,7 @@ static void qapi_dealloc_start_implicit_struct(Visitor *v,
     qapi_dealloc_push(qov, obj);
 }
 
-static void qapi_dealloc_end_implicit_struct(Visitor *v, Error **errp)
+static void qapi_dealloc_end_implicit_struct(Visitor *v)
 {
     QapiDeallocVisitor *qov = to_qov(v);
     void **obj = qapi_dealloc_pop(qov);
@@ -99,8 +100,7 @@ static void qapi_dealloc_start_list(Visitor *v, const char *name, Error **errp)
     qapi_dealloc_push(qov, NULL);
 }
 
-static GenericList *qapi_dealloc_next_list(Visitor *v, GenericList **listp,
-                                           Error **errp)
+static GenericList *qapi_dealloc_next_list(Visitor *v, GenericList **listp)
 {
     GenericList *list = *listp;
     QapiDeallocVisitor *qov = to_qov(v);
@@ -120,7 +120,7 @@ static GenericList *qapi_dealloc_next_list(Visitor *v, GenericList **listp,
     return NULL;
 }
 
-static void qapi_dealloc_end_list(Visitor *v, Error **errp)
+static void qapi_dealloc_end_list(Visitor *v)
 {
     QapiDeallocVisitor *qov = to_qov(v);
     void *obj = qapi_dealloc_pop(qov);

qapi/qapi-visit-core.c

@@ -38,10 +38,10 @@ void visit_start_implicit_struct(Visitor *v, void **obj, size_t size,
     }
 }
 
-void visit_end_implicit_struct(Visitor *v, Error **errp)
+void visit_end_implicit_struct(Visitor *v)
 {
     if (v->end_implicit_struct) {
-        v->end_implicit_struct(v, errp);
+        v->end_implicit_struct(v);
     }
 }
 
@@ -50,14 +50,14 @@ void visit_start_list(Visitor *v, const char *name, Error **errp)
     v->start_list(v, name, errp);
 }
 
-GenericList *visit_next_list(Visitor *v, GenericList **list, Error **errp)
+GenericList *visit_next_list(Visitor *v, GenericList **list)
 {
-    return v->next_list(v, list, errp);
+    return v->next_list(v, list);
 }
 
-void visit_end_list(Visitor *v, Error **errp)
+void visit_end_list(Visitor *v)
 {
-    v->end_list(v, errp);
+    v->end_list(v);
 }
 
 bool visit_start_union(Visitor *v, bool data_present, Error **errp)

qapi/qmp-input-visitor.c

@@ -1,6 +1,7 @@
 /*
  * Input Visitor
  *
+ * Copyright (C) 2012-2016 Red Hat, Inc.
  * Copyright IBM, Corp. 2011
  *
  * Authors:
@@ -154,10 +155,6 @@ static void qmp_input_start_implicit_struct(Visitor *v, void **obj,
     }
 }
 
-static void qmp_input_end_implicit_struct(Visitor *v, Error **errp)
-{
-}
-
 static void qmp_input_start_list(Visitor *v, const char *name, Error **errp)
 {
     QmpInputVisitor *qiv = to_qiv(v);
@@ -172,8 +169,7 @@ static void qmp_input_start_list(Visitor *v, const char *name, Error **errp)
     qmp_input_push(qiv, qobj, errp);
 }
 
-static GenericList *qmp_input_next_list(Visitor *v, GenericList **list,
-                                        Error **errp)
+static GenericList *qmp_input_next_list(Visitor *v, GenericList **list)
 {
     QmpInputVisitor *qiv = to_qiv(v);
     GenericList *entry;
@@ -202,7 +198,7 @@ static GenericList *qmp_input_next_list(Visitor *v, GenericList **list,
     return entry;
 }
 
-static void qmp_input_end_list(Visitor *v, Error **errp)
+static void qmp_input_end_list(Visitor *v)
 {
     QmpInputVisitor *qiv = to_qiv(v);
 
@@ -353,7 +349,6 @@ QmpInputVisitor *qmp_input_visitor_new(QObject *obj)
     v->visitor.start_struct = qmp_input_start_struct;
     v->visitor.end_struct = qmp_input_end_struct;
     v->visitor.start_implicit_struct = qmp_input_start_implicit_struct;
-    v->visitor.end_implicit_struct = qmp_input_end_implicit_struct;
     v->visitor.start_list = qmp_input_start_list;
     v->visitor.next_list = qmp_input_next_list;
     v->visitor.end_list = qmp_input_end_list;

qapi/qmp-output-visitor.c

@@ -1,6 +1,7 @@
 /*
  * Core Definitions for QAPI/QMP Command Registry
  *
+ * Copyright (C) 2012-2016 Red Hat, Inc.
  * Copyright IBM, Corp. 2011
  *
  * Authors:
@@ -136,8 +137,7 @@ static void qmp_output_start_list(Visitor *v, const char *name, Error **errp)
     qmp_output_push(qov, list);
 }
 
-static GenericList *qmp_output_next_list(Visitor *v, GenericList **listp,
-                                         Error **errp)
+static GenericList *qmp_output_next_list(Visitor *v, GenericList **listp)
 {
     GenericList *list = *listp;
     QmpOutputVisitor *qov = to_qov(v);
@@ -152,7 +152,7 @@ static GenericList *qmp_output_next_list(Visitor *v, GenericList **listp,
     return list ? list->next : NULL;
 }
 
-static void qmp_output_end_list(Visitor *v, Error **errp)
+static void qmp_output_end_list(Visitor *v)
 {
     QmpOutputVisitor *qov = to_qov(v);
     qmp_output_pop(qov);

qapi/string-input-visitor.c

@@ -1,7 +1,7 @@
 /*
  * String parsing visitor
  *
- * Copyright Red Hat, Inc. 2012
+ * Copyright Red Hat, Inc. 2012-2016
  *
  * Author: Paolo Bonzini <pbonzini@redhat.com>
  *
@@ -139,8 +139,7 @@ start_list(Visitor *v, const char *name, Error **errp)
     }
 }
 
-static GenericList *
-next_list(Visitor *v, GenericList **list, Error **errp)
+static GenericList *next_list(Visitor *v, GenericList **list)
 {
     StringInputVisitor *siv = to_siv(v);
     GenericList **link;
@@ -178,8 +177,7 @@ next_list(Visitor *v, GenericList **list, Error **errp)
     return *link;
 }
 
-static void
-end_list(Visitor *v, Error **errp)
+static void end_list(Visitor *v)
 {
     StringInputVisitor *siv = to_siv(v);
     siv->head = true;

qapi/string-output-visitor.c

@@ -1,7 +1,7 @@
 /*
  * String printing Visitor
  *
- * Copyright Red Hat, Inc. 2012
+ * Copyright Red Hat, Inc. 2012-2016
  *
  * Author: Paolo Bonzini <pbonzini@redhat.com>
  *
@@ -276,8 +276,7 @@ start_list(Visitor *v, const char *name, Error **errp)
     sov->head = true;
 }
 
-static GenericList *
-next_list(Visitor *v, GenericList **list, Error **errp)
+static GenericList *next_list(Visitor *v, GenericList **list)
 {
     StringOutputVisitor *sov = to_sov(v);
     GenericList *ret = NULL;
@@ -303,8 +302,7 @@ next_list(Visitor *v, GenericList **list, Error **errp)
     return ret;
 }
 
-static void
-end_list(Visitor *v, Error **errp)
+static void end_list(Visitor *v)
 {
     StringOutputVisitor *sov = to_sov(v);
 

scripts/qapi-visit.py

@@ -62,7 +62,7 @@ def gen_visit_implicit_struct(typ):
     visit_start_implicit_struct(v, (void **)obj, sizeof(%(c_type)s), &err);
     if (!err) {
         visit_type_%(c_type)s_fields(v, obj, errp);
-        visit_end_implicit_struct(v, &err);
+        visit_end_implicit_struct(v);
     }
     error_propagate(errp, err);
 }
@@ -161,15 +161,13 @@ def gen_visit_list(name, element_type):
     }
 
     for (prev = (GenericList **)obj;
-         !err && (i = visit_next_list(v, prev, &err)) != NULL;
+         !err && (i = visit_next_list(v, prev)) != NULL;
          prev = &i) {
         %(c_name)s *native_i = (%(c_name)s *)i;
         visit_type_%(c_elt_type)s(v, NULL, &native_i->value, &err);
     }
 
-    error_propagate(errp, err);
-    err = NULL;
-    visit_end_list(v, &err);
+    visit_end_list(v);
 out:
     error_propagate(errp, err);
 }
@@ -230,9 +228,7 @@ def gen_visit_alternate(name, variants):
                    "%(name)s");
     }
 out_obj:
-    error_propagate(errp, err);
-    err = NULL;
-    visit_end_implicit_struct(v, &err);
+    visit_end_implicit_struct(v);
 out:
     error_propagate(errp, err);
 }