Show the offset, length and memory of uninit read errors #142673
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oli-obk
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Jun 18, 2025
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| throw_ub!(InvalidUninitBytes(None)); | ||
| throw_ub!(InvalidUninitBytes(match op.to_op(self)?.as_mplace_or_imm() { | ||
| Left(mplace) => mplace.ptr().provenance.and_then(|prov| { | ||
| let start = mplace.ptr().into_parts().1; | ||
| let size = op.layout().size; | ||
| let range = alloc_range(start, size); | ||
| Some((prov.get_alloc_id()?, BadBytesAccess { access: range, bad: range })) | ||
| }), | ||
| Right(_) => None, | ||
| })) |
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This one doesn't show up in diagnostics, but it seemed good to change it, too
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Why doesn't it show up in diagnostics? Aren't all the miri output diffs caused by exactly this?
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Ah no, that diff is probably caused by the read_scalar change.
If this logic here can't be tested, I'd rather remove it, given that it is currently wrong due to how it uses into_parts.
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#142839 gets rid of it
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This is read_immediate, #142839 does nothing there...?
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oh right, I mixed up things.
hmm. yea I think I just tried this one because I thought it should be hit somewhere. So I'll turn it into a span_bug
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ok, digging into this got more interesting. I added two more commits. TLDR: we only ever use Immediate::Uninit for zsts or for uninit locals. But reading uninit locals only happens by converting them to Operand, which handles uninit immediates if processed by erroring.
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That's kind of an accidental invariant though, I think... is it worth relying on?
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It allows some simplifications. lmk what you think about the latest commits and I can either restore the previous zst/uninit design, or we keep it and revisit if we notice there's something better to do with it (or matthias manages to fuzz us examples of how that code is actually reachable for non-zsts)
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ok, looks like mir opts use uninit a lot more, so I backed out that commit
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grml. I haven't been able to run miri's dep tests in-tree in forever. Always sth about libc not found. Will try to bless the others and hope none of these need blessing |
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The Miri subtree was changed cc @rust-lang/miri |
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RalfJung
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Jun 27, 2025
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| throw_ub!(InvalidUninitBytes(None)); | ||
| throw_ub!(InvalidUninitBytes(match op.to_op(self)?.as_mplace_or_imm() { | ||
| Left(mplace) => mplace.ptr().provenance.and_then(|prov| { | ||
| let start = mplace.ptr().into_parts().1; | ||
| let size = op.layout().size; | ||
| let range = alloc_range(start, size); | ||
| Some((prov.get_alloc_id()?, BadBytesAccess { access: range, bad: range })) | ||
| }), | ||
| Right(_) => None, | ||
| })) |
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Why doesn't it show up in diagnostics? Aren't all the miri output diffs caused by exactly this?
| throw_ub!(InvalidUninitBytes(None)); | ||
| throw_ub!(InvalidUninitBytes(match op.to_op(self)?.as_mplace_or_imm() { | ||
| Left(mplace) => mplace.ptr().provenance.and_then(|prov| { | ||
| let start = mplace.ptr().into_parts().1; |
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This is not correct -- depending on which type of provenance this is, start will be either relative to the allocation, or absolute. into_parts has a doc comment warning about this. :) Maybe we should rename it into_raw_parts or so to make it more clear that this API is somewhat dicey.
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☔ The latest upstream changes (presumably #143091) made this pull request unmergeable. Please resolve the merge conflicts. |
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Reminder, once the PR becomes ready for a review, use |
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Some changes occurred to MIR optimizations cc @rust-lang/wg-mir-opt |
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☔ The latest upstream changes (presumably #142839) made this pull request unmergeable. Please resolve the merge conflicts. |
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@rustbot ready |
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The job Click to see the possible cause of the failure (guessed by this bot) |
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@rustbot author Hmm miri validation hits that case apparently |
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r? @RalfJung
I want to improve memory dumps in general. Not sure yet how to do so best within rust diagnostics, but in a perfect world I could generate a dummy in-memory file (that contains the rendered memory dump) that we then can then provide regular rustc
Spans to. So we'd basically report normal diagnostics for them with squiggly lines and everything.