71 lines
1.8 KiB
Rust
71 lines
1.8 KiB
Rust
use std::mem;
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trait Answer {
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fn answer() -> Self;
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}
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impl Answer for i32 {
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fn answer() -> i32 {
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42
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}
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}
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// A generic function, to make its address unstable
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fn f<T: Answer>() -> T {
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Answer::answer()
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}
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fn g(i: i32) -> i32 {
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i*42
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}
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fn h(i: i32, j: i32) -> i32 {
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j * i * 7
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}
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fn return_fn_ptr(f: fn() -> i32) -> fn() -> i32 {
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f
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}
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fn call_fn_ptr() -> i32 {
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return_fn_ptr(f)()
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}
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fn indirect<F: Fn() -> i32>(f: F) -> i32 { f() }
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fn indirect_mut<F: FnMut() -> i32>(mut f: F) -> i32 { f() }
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fn indirect_once<F: FnOnce() -> i32>(f: F) -> i32 { f() }
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fn indirect2<F: Fn(i32) -> i32>(f: F) -> i32 { f(10) }
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fn indirect_mut2<F: FnMut(i32) -> i32>(mut f: F) -> i32 { f(10) }
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fn indirect_once2<F: FnOnce(i32) -> i32>(f: F) -> i32 { f(10) }
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fn indirect3<F: Fn(i32, i32) -> i32>(f: F) -> i32 { f(10, 3) }
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fn indirect_mut3<F: FnMut(i32, i32) -> i32>(mut f: F) -> i32 { f(10, 3) }
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fn indirect_once3<F: FnOnce(i32, i32) -> i32>(f: F) -> i32 { f(10, 3) }
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fn main() {
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assert_eq!(call_fn_ptr(), 42);
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assert_eq!(indirect(f), 42);
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assert_eq!(indirect_mut(f), 42);
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assert_eq!(indirect_once(f), 42);
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assert_eq!(indirect2(g), 420);
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assert_eq!(indirect_mut2(g), 420);
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assert_eq!(indirect_once2(g), 420);
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assert_eq!(indirect3(h), 210);
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assert_eq!(indirect_mut3(h), 210);
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assert_eq!(indirect_once3(h), 210);
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let g = f as fn() -> i32;
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assert!(return_fn_ptr(g) == g);
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assert!(return_fn_ptr(g) as unsafe fn() -> i32 == g as fn() -> i32 as unsafe fn() -> i32);
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assert!(return_fn_ptr(f) != f);
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// Any non-null value is okay for function pointers.
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unsafe {
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let _x: fn() = mem::transmute(1usize);
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let mut b = Box::new(42);
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let ptr = &mut *b as *mut _;
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drop(b);
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let _x: fn() = mem::transmute(ptr);
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}
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}
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