Are function pointers never dangling?

[xmh0511]

https://doc.rust-lang.org/stable/reference/behavior-considered-undefined.html#r-undefined.dangling says:

A reference/pointer is “dangling” if not all of the bytes it points to are part of the same live allocation (so in particular they all have to be part of some allocation).

According to https://doc.rust-lang.org/reference/types.html#r-type.kinds

Pointer types:

• References
• Raw pointers
• Function pointers

The function pointers are categorized into pointer types. However, a function pointer is never dangling in a program. This should be clarified in section r-undefined.dangling.

[ia0]

Isn't this a consequence of r-undefined.dangling.zero-size:

If the size is 0, then the pointer is trivially never “dangling” (even if it is a null pointer).

And r-type.fn-item.intro:

When referred to, a function item, or the constructor of a tuple-like struct or enum variant, yields a zero-sized value of its function item type.

[xmh0511]

Isn't this a consequence of r-undefined.dangling.zero-size:

If the size is 0, then the pointer is trivially never “dangling” (even if it is a null pointer).

And r-type.fn-item.intro:

When referred to, a function item, or the constructor of a tuple-like struct or enum variant, yields a zero-sized value of its function item type.

function pointer types and function item types are different things.

[ia0]

Yes, so I guess what's missing is a r-type.fn-pointer.size rule that says:

The size of the pointee type of a function pointer is zero.