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Fix stacked borrows invalidation in rustc_data_structures sip128

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It creates the src pointer first, which is then invalidated by a
unique borrow of the destination pointer. Swap the borrows around
to fix this. Found with miri.
This commit is contained in:
Nilstrieb 2022-06-03 22:03:21 +02:00
parent fc8b13cb96
commit 7e3bee6d8e
1 changed files with 2 additions and 1 deletions
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3
compiler/rustc_data_structures/src/sip128.rs
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@ -255,8 +255,9 @@ impl SipHasher128 {
// elements from spill (at most LEN - 1 bytes could have overflowed
// into the spill). The memcpy call is optimized away because the size
// is known. And the whole copy is optimized away for LEN == 1.
let dst = self.buf.as_mut_ptr() as *mut u8;
let src = self.buf.get_unchecked(BUFFER_SPILL_INDEX) as *const _ as *const u8;
ptr::copy_nonoverlapping(src, self.buf.as_mut_ptr() as *mut u8, LEN - 1);
ptr::copy_nonoverlapping(src, dst, LEN - 1);
// This function should only be called when the write fills the buffer.
// Therefore, when LEN == 1, the new `self.nbuf` must be zero.