77 lines
2.0 KiB
Rust
77 lines
2.0 KiB
Rust
// run-pass
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// Test that we don't duplicate storage for a variable that is moved to another
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// binding. This used to happen in the presence of unwind and drop edges (see
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// `complex` below.)
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//
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// The exact sizes here can change (we'd like to know when they do). What we
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// don't want to see is the `complex` generator size being upwards of 2048 bytes
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// (which would indicate it is reserving space for two copies of Foo.)
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//
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// See issue #59123 for a full explanation.
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// edition:2018
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// ignore-wasm32 issue #62807
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#![feature(generators, generator_trait)]
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use std::ops::Generator;
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const FOO_SIZE: usize = 1024;
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struct Foo([u8; FOO_SIZE]);
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impl Drop for Foo {
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fn drop(&mut self) {}
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}
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fn move_before_yield() -> impl Generator<Yield = (), Return = ()> {
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static || {
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let first = Foo([0; FOO_SIZE]);
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let _second = first;
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yield;
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// _second dropped here
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}
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}
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fn noop() {}
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fn move_before_yield_with_noop() -> impl Generator<Yield = (), Return = ()> {
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static || {
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let first = Foo([0; FOO_SIZE]);
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noop();
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let _second = first;
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yield;
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// _second dropped here
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}
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}
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// Today we don't have NRVO (we allocate space for both `first` and `second`,)
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// but we can overlap `first` with `_third`.
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fn overlap_move_points() -> impl Generator<Yield = (), Return = ()> {
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static || {
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let first = Foo([0; FOO_SIZE]);
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yield;
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let second = first;
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yield;
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let _third = second;
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yield;
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}
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}
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fn overlap_x_and_y() -> impl Generator<Yield = (), Return = ()>{
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static || {
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let x = Foo([0; FOO_SIZE]);
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yield;
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drop(x);
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let y = Foo([0; FOO_SIZE]);
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yield;
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drop(y);
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}
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}
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fn main() {
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assert_eq!(1028, std::mem::size_of_val(&move_before_yield()));
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assert_eq!(1032, std::mem::size_of_val(&move_before_yield_with_noop()));
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assert_eq!(2056, std::mem::size_of_val(&overlap_move_points()));
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assert_eq!(1032, std::mem::size_of_val(&overlap_x_and_y()));
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}
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