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Make sure we do not create an unaligned slice #42
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Looks good to me, thanks for the patch. Maybe an assert would be better than the comment? We can spare the cycles here. |
Sure, done. |
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Thanks again 👍. @llogiq Could we get a patch release for this? This shouldn't have actually caused any bad codegen but it'll help around rust-lang/rust#52972. |
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I just published 0.3.2. |
bors
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stabilize slice_align_to This is very hard to implement correctly, and leads to [serious bugs](llogiq/bytecount#42) when done incorrectly. Moreover, this is needed to be able to run code that opportunistically exploits alignment on miri. So code using `align_to`/`align_to_mut` gets the benefit of a well-tested implementation *and* of being able to run in miri to test for (some kinds of) UB. This PR also clarifies the guarantee wrt. the middle part being as long as possible. Should the docs say under which circumstances the middle part could be shorter? Currently, that can only happen when running in miri.
Centril
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…r=alexcrichton Add a debug_assert to Vec::set_len Following the precedent of rust-lang#52972, which found llogiq/bytecount#42. (This may well make a test fail; let's see what Travis says.)
Centril
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…r=alexcrichton Add a debug_assert to Vec::set_len Following the precedent of rust-lang#52972, which found llogiq/bytecount#42. (This may well make a test fail; let's see what Travis says.)
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Based on discussion in rust-lang/rust#52972:
References have to be always aligned. This includes
&[T], and it includes the case where the slice is empty.chunk_alignwas producing an unalignedmidpart when thecmp::min(..., d2)picked the RHS.So I pulled the conditional out of
cmp::min, returning early if the slice is so short that the aligned beginning is beyond the end of the slice.