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Diffstat (limited to '')
-rw-r--r-- | src/tools/clippy/tests/ui/repl_uninit.rs | 41 |
1 files changed, 41 insertions, 0 deletions
diff --git a/src/tools/clippy/tests/ui/repl_uninit.rs b/src/tools/clippy/tests/ui/repl_uninit.rs new file mode 100644 index 000000000..6c7e2b854 --- /dev/null +++ b/src/tools/clippy/tests/ui/repl_uninit.rs @@ -0,0 +1,41 @@ +#![allow(deprecated, invalid_value, clippy::uninit_assumed_init)] +#![warn(clippy::mem_replace_with_uninit)] + +use std::mem; + +fn might_panic<X>(x: X) -> X { + // in practice this would be a possibly-panicky operation + x +} + +fn main() { + let mut v = vec![0i32; 4]; + // the following is UB if `might_panic` panics + unsafe { + let taken_v = mem::replace(&mut v, mem::uninitialized()); + let new_v = might_panic(taken_v); + std::mem::forget(mem::replace(&mut v, new_v)); + } + + unsafe { + let taken_v = mem::replace(&mut v, mem::MaybeUninit::uninit().assume_init()); + let new_v = might_panic(taken_v); + std::mem::forget(mem::replace(&mut v, new_v)); + } + + unsafe { + let taken_v = mem::replace(&mut v, mem::zeroed()); + let new_v = might_panic(taken_v); + std::mem::forget(mem::replace(&mut v, new_v)); + } + + // this is silly but OK, because usize is a primitive type + let mut u: usize = 42; + let uref = &mut u; + let taken_u = unsafe { mem::replace(uref, mem::zeroed()) }; + *uref = taken_u + 1; + + // this is still not OK, because uninit + let taken_u = unsafe { mem::replace(uref, mem::uninitialized()) }; + *uref = taken_u + 1; +} |