30 lines
1005 B
Rust
30 lines
1005 B
Rust
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#![feature(untagged_unions)]
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// A callee may not read the destination of our `&mut` without
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// us noticing.
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// Thise code got carefully checked to not introduce any reborrows
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// that are not explicit in the source. Let's hope the compiler does not break this later!
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use std::mem;
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fn main() {
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let mut x: i32 = 15;
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let xref1 = &mut x;
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let xref1_sneaky: usize = unsafe { mem::transmute_copy(&xref1) };
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let xref2 = &mut *xref1; // derived from xref1, so using raw is still okay...
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callee(xref1_sneaky);
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let _val = *xref2; // ...but any use of it will invalidate our ref.
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//~^ ERROR: does not exist on the stack
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}
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fn callee(xref1: usize) {
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// Transmuting through a union to avoid retagging
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union UsizeToRef {
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from: usize,
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to: &'static mut i32,
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}
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let xref1 = UsizeToRef { from: xref1 };
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// Doing the deref and the transmute (through the union) in the same place expression
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// should avoid retagging.
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let _val = unsafe { *xref1.to };
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}
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