Hello Daniel,

It is because those button events aren't called immediately. They are called when there is some user action (They are called WHEN there is action (click/push, etc.).
Had they been called immediately you would have the same undefined behaviour.
On the other hand, MenuBar::Set() method calls the provided callback, and sets the menubar immediately, which leads to crash.

Hello Daniel,

Ah, that's my fault. Nevermind. (For some reason, the below macros reminded me of U++ internal macros used in the TheIDE layout editor.)