diff options
| -rw-r--r-- | library/core/src/ptr/mod.rs | 5 | ||||
| -rw-r--r-- | src/tools/miri/tests/pass/drop_in_place.rs | 12 |
2 files changed, 17 insertions, 0 deletions
diff --git a/library/core/src/ptr/mod.rs b/library/core/src/ptr/mod.rs index 51eb2bb4f0e..335fc861ae8 100644 --- a/library/core/src/ptr/mod.rs +++ b/library/core/src/ptr/mod.rs @@ -452,6 +452,11 @@ mod mut_ptr; /// /// This is almost the same as calling [`ptr::read`] and discarding /// the result, but has the following advantages: +// FIXME: say something more useful than "almost the same"? +// There are open questions here: `read` requires the value to be fully valid, e.g. if `T` is a +// `bool` it must be 0 or 1, if it is a reference then it must be dereferenceable. `drop_in_place` +// only requires that `*to_drop` be "valid for dropping" and we have not defined what that means. In +// Miri it currently (May 2024) requires nothing at all for types without drop glue. /// /// * It is *required* to use `drop_in_place` to drop unsized types like /// trait objects, because they can't be read out onto the stack and diff --git a/src/tools/miri/tests/pass/drop_in_place.rs b/src/tools/miri/tests/pass/drop_in_place.rs new file mode 100644 index 00000000000..0615a43c800 --- /dev/null +++ b/src/tools/miri/tests/pass/drop_in_place.rs @@ -0,0 +1,12 @@ +// Miri currently doesn't require types without drop glue to be +// valid when dropped. This test confirms that behavior. +// This is not a stable guarantee! + +use std::ptr; + +fn main() { + let mut not_a_bool = 13u8; + unsafe { + ptr::drop_in_place(&mut not_a_bool as *mut u8 as *mut bool) + }; +} |