CODEWITHSUNDEEP
memoryrustfunction-pointers
gnevesdev
gnevesdev

Reputation: 47

How is the size of a fuction pointer always the same?

Playing around with Rust I discovered this: function pointer sizes in Rust

How can the size of a function pointer be always the same? How do they know that the function pointer should point to a function with those specific arguments and return type then?

Upvotes: 0

Views: 510

Answers (1)

Peter Hall
Peter Hall

Reputation: 58805

A function pointer is always the same size because it's a pointer! Functions defined with fn are stored in static memory and are never moved around. A pointer is sufficient to reference them.

The arguments of the function are known at compile time, as part of the type. The type checker uses those to make sure that the function is being called correctly and to generate assembly instructions to actually call the function. At runtime, the fn pointer can be considered to be data, while the detailed information about the function arguments is encoded in the compiled instructions.

Upvotes: 3

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