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Test that we allow non-static lifetime transmutes

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This commit is contained in:
Devon Hollowood 2018-05-22 17:18:56 -07:00
parent 2a606b5220
commit 96b11a5888
2 changed files with 23 additions and 12 deletions
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19
tests/ui/transmute.rs
View file

@ -140,6 +140,21 @@ fn bytes_to_str(b: &[u8], mb: &mut [u8]) {
let _: &mut str = unsafe { std::mem::transmute(mb) };
}
// Make sure we can modify lifetimes, which is one of the recommended uses
// of transmute
// Make sure we can do static lifetime transmutes
#[warn(transmute_ptr_to_ptr)]
unsafe fn transmute_lifetime_to_static<'a, T>(t: &'a T) -> &'static T {
std::mem::transmute::<&'a T, &'static T>(t)
}
// Make sure we can do non-static lifetime transmutes
#[warn(transmute_ptr_to_ptr)]
unsafe fn transmute_lifetime<'a, 'b, T>(t: &'a T, u: &'b T) -> &'b T {
std::mem::transmute::<&'a T, &'b T>(t)
}
#[warn(transmute_ptr_to_ptr)]
fn transmute_ptr_to_ptr() {
let ptr = &1u32 as *const u32;
@ -159,10 +174,6 @@ fn transmute_ptr_to_ptr() {
let _ = mut_ptr as *mut f32;
let _ = unsafe { &*(&1u32 as *const u32 as *const f32) };
let _ = unsafe { &mut *(&mut 1u32 as *mut u32 as *mut f32) };
// This is just modifying the lifetime, and is one of the recommended uses
// of transmute
let n = 1u32;
let _ = unsafe { std::mem::transmute::<&'_ u32, &'static u32>(&n) };
}
fn main() { }

16
tests/ui/transmute.stderr
View file

@ -205,29 +205,29 @@ error: transmute from a `&mut [u8]` to a `&mut str`
| ^^^^^^^^^^^^^^^^^^^^^^^ help: consider using: `std::str::from_utf8_mut(mb).unwrap()`
error: transmute from a pointer to a pointer
--> $DIR/transmute.rs:149:29
--> $DIR/transmute.rs:164:29
|
149 | let _: *const f32 = std::mem::transmute(ptr);
164 | let _: *const f32 = std::mem::transmute(ptr);
| ^^^^^^^^^^^^^^^^^^^^^^^^ help: try: `ptr as *const f32`
|
= note: `-D transmute-ptr-to-ptr` implied by `-D warnings`
error: transmute from a pointer to a pointer
--> $DIR/transmute.rs:150:27
--> $DIR/transmute.rs:165:27
|
150 | let _: *mut f32 = std::mem::transmute(mut_ptr);
165 | let _: *mut f32 = std::mem::transmute(mut_ptr);
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: try: `mut_ptr as *mut f32`
error: transmute from a reference to a reference
--> $DIR/transmute.rs:152:23
--> $DIR/transmute.rs:167:23
|
152 | let _: &f32 = std::mem::transmute(&1u32);
167 | let _: &f32 = std::mem::transmute(&1u32);
| ^^^^^^^^^^^^^^^^^^^^^^^^^^ help: try: `&*(&1u32 as *const u32 as *const f32)`
error: transmute from a reference to a reference
--> $DIR/transmute.rs:153:27
--> $DIR/transmute.rs:168:27
|
153 | let _: &mut f32 = std::mem::transmute(&mut 1u32);
168 | let _: &mut f32 = std::mem::transmute(&mut 1u32);
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: try: `&mut *(&mut 1u32 as *mut u32 as *mut f32)`
error: aborting due to 36 previous errors