Callback's flaws

Question

From: http://doc.qt.nokia.com/4.7/signalsandslots.html

Callbacks have two fundamental flaws: Firstly, they are not type-safe. We can never be certain

Answer 1

It's a pointer to a function, and some compilers don't check that in run time there won't be a case where that pointer leads to a function with different parameters than expected.