Implement posix_fallocate with set_len() functionality
#4664
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| let new_size = match offset.checked_add(len) { | ||
| // u64::from(i128) can fail if: | ||
| // - the value is negative, but we checed this above with `offset < 0 || len <= 0` | ||
| // - the value is too big/small to fit in u64, this should not happen since the callers | ||
| // check if the value is a `i32` or `i64`. | ||
| // So this unwrap is safe to do. | ||
| Some(size) => u64::try_from(size).unwrap(), |
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I'm actually unsure if this is allowed in Miri, the callers to check if they fit inside of the layout.size, which can only be libc::off_t(i32) or libc::off64_t(i64).
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Oh so we are adding two i64 here and hence the result fits in a u64?
Is that what the docs say for this function? I would kind of expect that there would be a "too big" error if the result exceeds i64::MAX.
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I should have asked this sooner, excuse me. The docs do not say anything about integer overflows, but it does specify returning "EFBIG" when this size is larger than the maximum file size. I assumed we should thus return "EFBIG" when the addition overflows.
But I don't know how to get the maximum file size in Miri.
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I think the maximum file size is i64::MAX.
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then this should be correct right?
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This PR was rebased onto a different master commit. Here's a range-diff highlighting what actually changed. Rebasing is a normal part of keeping PRs up to date, so no action is needed—this note is just to help reviewers. |
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Had to rebase because of the new |
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should close #4464.
I used this man page for the implementation.
Changes included in this pr:
posix_fallocateandposix_fallocate64(same as truncate versions because of libc::off_t)unix/foreign_items.pass-dep/libc/libc-fs.rs.