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miri: support 'promising' alignment for symbolic alignment check

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This commit is contained in:
Ralf Jung
2023-11-12 16:06:50 +01:00
parent 7ceaf19868
commit bebba4f6e0
14 changed files with 298 additions and 118 deletions
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27
library/core/src/slice/mod.rs
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@@ -3868,6 +3868,18 @@ impl<T> [T] {
} else {
let (left, rest) = self.split_at(offset);
let (us_len, ts_len) = rest.align_to_offsets::<U>();
// Inform Miri that we want to consider the "middle" pointer to be suitably aligned.
#[cfg(miri)]
{
extern "Rust" {
pub fn miri_promise_symbolic_alignment(ptr: *const (), align: usize);
}
// SAFETY: this call is always safe.
unsafe {
miri_promise_symbolic_alignment(rest.as_ptr().cast(), mem::align_of::<U>());
}
}
// SAFETY: now `rest` is definitely aligned, so `from_raw_parts` below is okay,
// since the caller guarantees that we can transmute `T` to `U` safely.
unsafe {
@@ -3938,6 +3950,21 @@ impl<T> [T] {
let (us_len, ts_len) = rest.align_to_offsets::<U>();
let rest_len = rest.len();
let mut_ptr = rest.as_mut_ptr();
// Inform Miri that we want to consider the "middle" pointer to be suitably aligned.
#[cfg(miri)]
{
extern "Rust" {
pub fn miri_promise_symbolic_alignment(ptr: *const (), align: usize);
}
// SAFETY: this call is always safe.
unsafe {
miri_promise_symbolic_alignment(
mut_ptr.cast() as *const (),
mem::align_of::<U>(),
);
}
}
// We can't use `rest` again after this, that would invalidate its alias `mut_ptr`!
// SAFETY: see comments for `align_to`.
unsafe {