qom: Clean up fragile use of error_is_set() in set() methods

Using error_is_set(ERRP) to find out whether a function failed is
either wrong, fragile, or unnecessarily opaque.  It's wrong when ERRP
may be null, because errors go undetected when it is.  It's fragile
when proving ERRP non-null involves a non-local argument.  Else, it's
unnecessarily opaque (see commit 84d18f0).

I guess the error_is_set(errp) in the ObjectProperty set() methods are
merely fragile right now, because I can't find a call chain that
passes a null errp argument.

Make the code more robust and more obviously correct: receive the
error in a local variable, then propagate it through the parameter.

Signed-off-by: Markus Armbruster <armbru@redhat.com>
Signed-off-by: Andreas Färber <afaerber@suse.de>

1 files changed, 7 insertions, 4 deletions

diff --git a/hw/core/qdev-properties.c b/hw/core/qdev-properties.c
index 585a8e902e..d8cb5408c3 100644
--- a/hw/core/qdev-properties.c
+++ b/hw/core/qdev-properties.c
@@ -751,6 +751,7 @@ static void set_prop_arraylen(Object *obj, Visitor *v, void *opaque,
     Property *prop = opaque;
     uint32_t *alenptr = qdev_get_prop_ptr(dev, prop);
     void **arrayptr = (void *)dev + prop->arrayoffset;
+    Error *local_err = NULL;
     void *eltptr;
     const char *arrayname;
     int i;
@@ -764,8 +765,9 @@ static void set_prop_arraylen(Object *obj, Visitor *v, void *opaque,
                    name);
         return;
     }
-    visit_type_uint32(v, alenptr, name, errp);
-    if (error_is_set(errp)) {
+    visit_type_uint32(v, alenptr, name, &local_err);
+    if (local_err) {
+        error_propagate(errp, local_err);
         return;
     }
     if (!*alenptr) {
@@ -802,8 +804,9 @@ static void set_prop_arraylen(Object *obj, Visitor *v, void *opaque,
                             arrayprop->prop.info->get,
                             arrayprop->prop.info->set,
                             array_element_release,
-                            arrayprop, errp);
-        if (error_is_set(errp)) {
+                            arrayprop, &local_err);
+        if (local_err) {
+            error_propagate(errp, local_err);
             return;
         }
     }