Object: assert callbacks exists

Improves stacktraces.

Current stacktrace:
  ./htop(backtrace+0x5b)[0x45d98b]
  ./htop(CRT_handleSIGSEGV+0x189)[0x4eb5e9]
  /lib/x86_64-linux-gnu/libpthread.so.0(+0x14140)[0x7fbbfb1ea140]

New:
  ./htop(backtrace+0x5b)[0x45d98b]
  ./htop(CRT_handleSIGSEGV+0x189)[0x4eb7f9]
  /lib/x86_64-linux-gnu/libpthread.so.0(+0x14140)[0x7f62b0a65140]
  /lib/x86_64-linux-gnu/libc.so.6(gsignal+0x141)[0x7f62b089ac41]
  /lib/x86_64-linux-gnu/libc.so.6(abort+0x123)[0x7f62b0884537]
  /lib/x86_64-linux-gnu/libc.so.6(+0x2540f)[0x7f62b088440f]
  /lib/x86_64-linux-gnu/libc.so.6(+0x345c2)[0x7f62b08935c2]
  ./htop(Vector_delete+0x873)[0x54b303]
  ./htop(Panel_done+0x7b)[0x51abbb]
  ./htop[0x4ed8ee]
  ./htop(Vector_delete+0x414)[0x54aea4]
  ./htop(ScreenManager_delete+0x37)[0x536ea7]
  ./htop[0x4d9d1a]
  ./htop[0x4d5516]
  ./htop[0x5078d7]
  ./htop(ScreenManager_run+0x69f)[0x5388bf]
  ./htop(main+0x7c6)[0x4fcf76]
  /lib/x86_64-linux-gnu/libc.so.6(__libc_start_main+0xea)[0x7f62b0885cca]
  ./htop(_start+0x2a)[0x42688a]

1 files changed, 7 insertions, 3 deletions

diff --git a/Object.h b/Object.h
index 05a9a72d..2c3ba9f9 100644
--- a/Object.h
+++ b/Object.h
@@ -8,6 +8,10 @@ Released under the GNU GPLv2, see the COPYING file
 in the source distribution for its full text.
 */
 
+#include "config.h" // IWYU pragma: keep
+
+#include <assert.h>
+
 #include "RichString.h"
 #include "XUtils.h" // IWYU pragma: keep
 
@@ -26,10 +30,10 @@ typedef void(*Object_Delete)(Object*);
 #define Object_getClass(obj_)         ((const Object*)(obj_))->klass
 #define Object_setClass(obj_, class_) (((Object*)(obj_))->klass = (const ObjectClass*) (class_))
 
-#define Object_delete(obj_)           Object_getClass(obj_)->delete((Object*)(obj_))
+#define Object_delete(obj_)           (assert(Object_getClass(obj_)->delete), Object_getClass(obj_)->delete((Object*)(obj_)))
 #define Object_displayFn(obj_)        Object_getClass(obj_)->display
-#define Object_display(obj_, str_)    Object_getClass(obj_)->display((const Object*)(obj_), str_)
-#define Object_compare(obj_, other_)  Object_getClass(obj_)->compare((const void*)(obj_), other_)
+#define Object_display(obj_, str_)    (assert(Object_getClass(obj_)->display), Object_getClass(obj_)->display((const Object*)(obj_), str_))
+#define Object_compare(obj_, other_)  (assert(Object_getClass(obj_)->compare), Object_getClass(obj_)->compare((const void*)(obj_), other_))
 
 #define Class(class_)                 ((const ObjectClass*)(&(class_ ## _class)))