qom: trace asserting casts

This provides a way to detect the cast that leads to a (reproducible)
crash even when QOM cast debugging is disabled.
Signed-off-by: NPaolo Bonzini <pbonzini@redhat.com>
Message-id: 1368188203-3407-6-git-send-email-pbonzini@redhat.com
Signed-off-by: NAnthony Liguori <aliguori@us.ibm.com>

qom/object.c

@@ -16,6 +16,7 @@
 #include "qapi/string-input-visitor.h"
 #include "qapi/string-output-visitor.h"
 #include "qapi/qmp/qerror.h"
+#include "trace.h"
 
 /* TODO: replace QObject with a simpler visitor to avoid a dependency
  * of the QOM core on QObject?  */
@@ -436,6 +437,9 @@ Object *object_dynamic_cast_assert(Object *obj, const char *typename,
 {
     Object *inst;
 
+    trace_object_dynamic_cast_assert(obj ? obj->class->type->name : "(null)",
+                                     typename, file, line, func);
+
     inst = object_dynamic_cast(obj, typename);
 
     if (!inst && obj) {
@@ -500,8 +504,12 @@ ObjectClass *object_class_dynamic_cast_assert(ObjectClass *class,
                                               const char *file, int line,
                                               const char *func)
 {
-    ObjectClass *ret = object_class_dynamic_cast(class, typename);
+    ObjectClass *ret;
+
+    trace_object_class_dynamic_cast_assert(class ? class->type->name : "(null)",
+                                           typename, file, line, func);
 
+    ret = object_class_dynamic_cast(class, typename);
     if (!ret && class) {
         fprintf(stderr, "%s:%d:%s: Object %p is not an instance of type %s\n",
                 file, line, func, class, typename);

trace-events

@@ -1160,3 +1160,6 @@ kvm_vm_ioctl(int type, void *arg) "type %d, arg %p"
 kvm_vcpu_ioctl(int cpu_index, int type, void *arg) "cpu_index %d, type %d, arg %p"
 kvm_run_exit(int cpu_index, uint32_t reason) "cpu_index %d, reason %d"
 
+# qom/object.c
+object_dynamic_cast_assert(const char *type, const char *target, const char *file, int line, const char *func) "%s->%s (%s:%d:%s)"
+object_class_dynamic_cast_assert(const char *type, const char *target, const char *file, int line, const char *func) "%s->%s (%s:%d:%s)"