qapi: Avoid use of misnamed DO_UPCAST()

The macro DO_UPCAST() is incorrectly named: it converts from a
parent class to a derived class (which is a downcast).  Better,
and more consistent with some of the other qapi visitors, is
to use the container_of() macro through a to_FOO() helper.  Names
like 'to_ov()' may be a bit short, but for a static helper it
doesn't hurt too much, and matches existing practice in files
like qmp-input-visitor.c.

Our current definition of container_of() is weaker than
DO_UPCAST(), in that it does not require the derived class to
have Visitor as its first member, but this does not hurt our
usage patterns in qapi visitors.

Signed-off-by: Eric Blake <eblake@redhat.com>
Reviewed-by: Marc-André Lureau <marcandre.lureau@redhat.com>
Message-Id: <1454075341-13658-3-git-send-email-eblake@redhat.com>
Signed-off-by: Markus Armbruster <armbru@redhat.com>

qapi/opts-visitor.c

@@ -90,6 +90,12 @@ struct OptsVisitor
 };
 
 
+static OptsVisitor *to_ov(Visitor *v)
+{
+    return container_of(v, OptsVisitor, visitor);
+}
+
+
 static void
 destroy_list(gpointer list)
 {
@@ -122,7 +128,7 @@ static void
 opts_start_struct(Visitor *v, void **obj, const char *kind,
                   const char *name, size_t size, Error **errp)
 {
-    OptsVisitor *ov = DO_UPCAST(OptsVisitor, visitor, v);
+    OptsVisitor *ov = to_ov(v);
     const QemuOpt *opt;
 
     if (obj) {
@@ -161,7 +167,7 @@ ghr_true(gpointer ign_key, gpointer ign_value, gpointer ign_user_data)
 static void
 opts_end_struct(Visitor *v, Error **errp)
 {
-    OptsVisitor *ov = DO_UPCAST(OptsVisitor, visitor, v);
+    OptsVisitor *ov = to_ov(v);
     GQueue *any;
 
     if (--ov->depth > 0) {
@@ -203,7 +209,7 @@ lookup_distinct(const OptsVisitor *ov, const char *name, Error **errp)
 static void
 opts_start_list(Visitor *v, const char *name, Error **errp)
 {
-    OptsVisitor *ov = DO_UPCAST(OptsVisitor, visitor, v);
+    OptsVisitor *ov = to_ov(v);
 
     /* we can't traverse a list in a list */
     assert(ov->list_mode == LM_NONE);
@@ -217,7 +223,7 @@ opts_start_list(Visitor *v, const char *name, Error **errp)
 static GenericList *
 opts_next_list(Visitor *v, GenericList **list, Error **errp)
 {
-    OptsVisitor *ov = DO_UPCAST(OptsVisitor, visitor, v);
+    OptsVisitor *ov = to_ov(v);
     GenericList **link;
 
     switch (ov->list_mode) {
@@ -266,7 +272,7 @@ opts_next_list(Visitor *v, GenericList **list, Error **errp)
 static void
 opts_end_list(Visitor *v, Error **errp)
 {
-    OptsVisitor *ov = DO_UPCAST(OptsVisitor, visitor, v);
+    OptsVisitor *ov = to_ov(v);
 
     assert(ov->list_mode == LM_STARTED ||
            ov->list_mode == LM_IN_PROGRESS ||
@@ -308,7 +314,7 @@ processed(OptsVisitor *ov, const char *name)
 static void
 opts_type_str(Visitor *v, char **obj, const char *name, Error **errp)
 {
-    OptsVisitor *ov = DO_UPCAST(OptsVisitor, visitor, v);
+    OptsVisitor *ov = to_ov(v);
     const QemuOpt *opt;
 
     opt = lookup_scalar(ov, name, errp);
@@ -324,7 +330,7 @@ opts_type_str(Visitor *v, char **obj, const char *name, Error **errp)
 static void
 opts_type_bool(Visitor *v, bool *obj, const char *name, Error **errp)
 {
-    OptsVisitor *ov = DO_UPCAST(OptsVisitor, visitor, v);
+    OptsVisitor *ov = to_ov(v);
     const QemuOpt *opt;
 
     opt = lookup_scalar(ov, name, errp);
@@ -357,7 +363,7 @@ opts_type_bool(Visitor *v, bool *obj, const char *name, Error **errp)
 static void
 opts_type_int(Visitor *v, int64_t *obj, const char *name, Error **errp)
 {
-    OptsVisitor *ov = DO_UPCAST(OptsVisitor, visitor, v);
+    OptsVisitor *ov = to_ov(v);
     const QemuOpt *opt;
     const char *str;
     long long val;
@@ -413,7 +419,7 @@ opts_type_int(Visitor *v, int64_t *obj, const char *name, Error **errp)
 static void
 opts_type_uint64(Visitor *v, uint64_t *obj, const char *name, Error **errp)
 {
-    OptsVisitor *ov = DO_UPCAST(OptsVisitor, visitor, v);
+    OptsVisitor *ov = to_ov(v);
     const QemuOpt *opt;
     const char *str;
     unsigned long long val;
@@ -465,7 +471,7 @@ opts_type_uint64(Visitor *v, uint64_t *obj, const char *name, Error **errp)
 static void
 opts_type_size(Visitor *v, uint64_t *obj, const char *name, Error **errp)
 {
-    OptsVisitor *ov = DO_UPCAST(OptsVisitor, visitor, v);
+    OptsVisitor *ov = to_ov(v);
     const QemuOpt *opt;
     int64_t val;
     char *endptr;
@@ -491,7 +497,7 @@ opts_type_size(Visitor *v, uint64_t *obj, const char *name, Error **errp)
 static void
 opts_optional(Visitor *v, bool *present, const char *name)
 {
-    OptsVisitor *ov = DO_UPCAST(OptsVisitor, visitor, v);
+    OptsVisitor *ov = to_ov(v);
 
     /* we only support a single mandatory scalar field in a list node */
     assert(ov->list_mode == LM_NONE);

qapi/string-input-visitor.c

@@ -33,6 +33,11 @@ struct StringInputVisitor
     const char *string;
 };
 
+static StringInputVisitor *to_siv(Visitor *v)
+{
+    return container_of(v, StringInputVisitor, visitor);
+}
+
 static void free_range(void *range, void *dummy)
 {
     g_free(range);
@@ -121,7 +126,7 @@ error:
 static void
 start_list(Visitor *v, const char *name, Error **errp)
 {
-    StringInputVisitor *siv = DO_UPCAST(StringInputVisitor, visitor, v);
+    StringInputVisitor *siv = to_siv(v);
 
     parse_str(siv, errp);
 
@@ -137,7 +142,7 @@ start_list(Visitor *v, const char *name, Error **errp)
 static GenericList *
 next_list(Visitor *v, GenericList **list, Error **errp)
 {
-    StringInputVisitor *siv = DO_UPCAST(StringInputVisitor, visitor, v);
+    StringInputVisitor *siv = to_siv(v);
     GenericList **link;
     Range *r;
 
@@ -176,14 +181,14 @@ next_list(Visitor *v, GenericList **list, Error **errp)
 static void
 end_list(Visitor *v, Error **errp)
 {
-    StringInputVisitor *siv = DO_UPCAST(StringInputVisitor, visitor, v);
+    StringInputVisitor *siv = to_siv(v);
     siv->head = true;
 }
 
 static void parse_type_int(Visitor *v, int64_t *obj, const char *name,
                            Error **errp)
 {
-    StringInputVisitor *siv = DO_UPCAST(StringInputVisitor, visitor, v);
+    StringInputVisitor *siv = to_siv(v);
 
     if (!siv->string) {
         error_setg(errp, QERR_INVALID_PARAMETER_TYPE, name ? name : "null",
@@ -225,7 +230,7 @@ error:
 static void parse_type_size(Visitor *v, uint64_t *obj, const char *name,
                             Error **errp)
 {
-    StringInputVisitor *siv = DO_UPCAST(StringInputVisitor, visitor, v);
+    StringInputVisitor *siv = to_siv(v);
     Error *err = NULL;
     uint64_t val;
 
@@ -247,7 +252,7 @@ static void parse_type_size(Visitor *v, uint64_t *obj, const char *name,
 static void parse_type_bool(Visitor *v, bool *obj, const char *name,
                             Error **errp)
 {
-    StringInputVisitor *siv = DO_UPCAST(StringInputVisitor, visitor, v);
+    StringInputVisitor *siv = to_siv(v);
 
     if (siv->string) {
         if (!strcasecmp(siv->string, "on") ||
@@ -271,7 +276,7 @@ static void parse_type_bool(Visitor *v, bool *obj, const char *name,
 static void parse_type_str(Visitor *v, char **obj, const char *name,
                            Error **errp)
 {
-    StringInputVisitor *siv = DO_UPCAST(StringInputVisitor, visitor, v);
+    StringInputVisitor *siv = to_siv(v);
     if (siv->string) {
         *obj = g_strdup(siv->string);
     } else {
@@ -283,7 +288,7 @@ static void parse_type_str(Visitor *v, char **obj, const char *name,
 static void parse_type_number(Visitor *v, double *obj, const char *name,
                               Error **errp)
 {
-    StringInputVisitor *siv = DO_UPCAST(StringInputVisitor, visitor, v);
+    StringInputVisitor *siv = to_siv(v);
     char *endp = (char *) siv->string;
     double val;
 
@@ -302,7 +307,7 @@ static void parse_type_number(Visitor *v, double *obj, const char *name,
 
 static void parse_optional(Visitor *v, bool *present, const char *name)
 {
-    StringInputVisitor *siv = DO_UPCAST(StringInputVisitor, visitor, v);
+    StringInputVisitor *siv = to_siv(v);
 
     if (!siv->string) {
         *present = false;

qapi/string-output-visitor.c

@@ -67,6 +67,11 @@ struct StringOutputVisitor
     GList *ranges;
 };
 
+static StringOutputVisitor *to_sov(Visitor *v)
+{
+    return container_of(v, StringOutputVisitor, visitor);
+}
+
 static void string_output_set(StringOutputVisitor *sov, char *string)
 {
     if (sov->string) {
@@ -120,7 +125,7 @@ static void format_string(StringOutputVisitor *sov, Range *r, bool next,
 static void print_type_int(Visitor *v, int64_t *obj, const char *name,
                            Error **errp)
 {
-    StringOutputVisitor *sov = DO_UPCAST(StringOutputVisitor, visitor, v);
+    StringOutputVisitor *sov = to_sov(v);
     GList *l;
 
     switch (sov->list_mode) {
@@ -196,7 +201,7 @@ static void print_type_int(Visitor *v, int64_t *obj, const char *name,
 static void print_type_size(Visitor *v, uint64_t *obj, const char *name,
                            Error **errp)
 {
-    StringOutputVisitor *sov = DO_UPCAST(StringOutputVisitor, visitor, v);
+    StringOutputVisitor *sov = to_sov(v);
     static const char suffixes[] = { 'B', 'K', 'M', 'G', 'T', 'P', 'E' };
     uint64_t div, val;
     char *out;
@@ -227,14 +232,14 @@ static void print_type_size(Visitor *v, uint64_t *obj, const char *name,
 static void print_type_bool(Visitor *v, bool *obj, const char *name,
                             Error **errp)
 {
-    StringOutputVisitor *sov = DO_UPCAST(StringOutputVisitor, visitor, v);
+    StringOutputVisitor *sov = to_sov(v);
     string_output_set(sov, g_strdup(*obj ? "true" : "false"));
 }
 
 static void print_type_str(Visitor *v, char **obj, const char *name,
                            Error **errp)
 {
-    StringOutputVisitor *sov = DO_UPCAST(StringOutputVisitor, visitor, v);
+    StringOutputVisitor *sov = to_sov(v);
     char *out;
 
     if (sov->human) {
@@ -248,14 +253,14 @@ static void print_type_str(Visitor *v, char **obj, const char *name,
 static void print_type_number(Visitor *v, double *obj, const char *name,
                               Error **errp)
 {
-    StringOutputVisitor *sov = DO_UPCAST(StringOutputVisitor, visitor, v);
+    StringOutputVisitor *sov = to_sov(v);
     string_output_set(sov, g_strdup_printf("%f", *obj));
 }
 
 static void
 start_list(Visitor *v, const char *name, Error **errp)
 {
-    StringOutputVisitor *sov = DO_UPCAST(StringOutputVisitor, visitor, v);
+    StringOutputVisitor *sov = to_sov(v);
 
     /* we can't traverse a list in a list */
     assert(sov->list_mode == LM_NONE);
@@ -266,7 +271,7 @@ start_list(Visitor *v, const char *name, Error **errp)
 static GenericList *
 next_list(Visitor *v, GenericList **list, Error **errp)
 {
-    StringOutputVisitor *sov = DO_UPCAST(StringOutputVisitor, visitor, v);
+    StringOutputVisitor *sov = to_sov(v);
     GenericList *ret = NULL;
     if (*list) {
         if (sov->head) {
@@ -293,7 +298,7 @@ next_list(Visitor *v, GenericList **list, Error **errp)
 static void
 end_list(Visitor *v, Error **errp)
 {
-    StringOutputVisitor *sov = DO_UPCAST(StringOutputVisitor, visitor, v);
+    StringOutputVisitor *sov = to_sov(v);
 
     assert(sov->list_mode == LM_STARTED ||
            sov->list_mode == LM_END ||