Closed
Description
What it does
Check a mistaken casting function item to usize or all other integer primitive types.
Categories (optional)
- Kind: correctness or pedantic
What is the advantage of the recommended code over the original code
- It is a mistake to cast a function item to
usizeinstead of getting function result.
This could be unnotice for a long time. - If you want to get pointer address of a function, explicitly cast it to function pointer and
usize. - Explicit is better than implicit.
The bug appeared in real code: rust-lang/rustup@5d9d980
I was author of the bug :) .
Drawbacks
It is verbose and somewhat redundant.
Example
use std::mem::size_of;
extern "C" {
fn foo(len: usize);
}
unsafe {
foo(size_of::<usize> as usize);
}Could be written as:
unsafe {
foo(size_of::<usize>());
// or
foo(size_of::<usize> as fn() -> usize as usize);
// or
foo(size_of::<usize> as *const () as usize);
}