Why are function objects better than function pointers?

Question

from Wikipedia - Function object

A typical use of a function object is in writing callback functions. A callback in procedural languages, such as C, may be performed by using function pointers.[2] However it can be difficult or awkward to pass a state into or out of the callback function. This restriction also inhibits more dynamic behavior of the function. A function object solves those problems since the function is really a façade for a full object, carrying its own state.

1. Why do function pointers make it difficult to pass a state into or out of the callback function and dynamic behavior of the function?

2. if function do not use function pointer how programs can called function

Answer 1

1. As far as function pointers in C go, you need to pass the state as an extra parameter. That's in opposition to languages like python, javascript or C++ that have closures. And that means storage duration needs to be considered for that extra structure.

2. C programmers do make use of function pointers. And you can't write very generic code without using function pointers. We just apply discipline and pass the captured state in a structure, as a function parameter.