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Rollup merge of #82804 - alexcrichton:fix-wasi, r=pnkfelix

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std: Fix a bug on the wasm32-wasi target opening files

This commit fixes an issue pointed out in #82758 where LTO changed the
behavior of a program. It turns out that LTO was not at fault here, it
simply uncovered an existing bug. The bindings to
`__wasilibc_find_relpath` assumed that the relative portion of the path
returned was always contained within thee input `buf` we passed in. This
isn't actually the case, however, and sometimes the relative portion of
the path may reference a sub-portion of the input string itself.

The fix here is to use the relative path pointer coming out of
`__wasilibc_find_relpath` as the source of truth. The `buf` used for
local storage is discarded in this function and the relative path is
copied out unconditionally. We might be able to get away with some
`Cow`-like business or such to avoid the extra allocation, but for now
this is probably the easiest patch to fix the original issue.
This commit is contained in:
Yuki Okushi 2021-03-14 13:07:33 +09:00 committed by GitHub
commit 9ce0820eef
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1 changed files with 2 additions and 4 deletions
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6
library/std/src/sys/wasi/fs.rs
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@ -650,13 +650,11 @@ fn open_parent(p: &Path) -> io::Result<(ManuallyDrop<WasiFd>, PathBuf)> {
);
return Err(io::Error::new(io::ErrorKind::Other, msg));
}
let len = CStr::from_ptr(buf.as_ptr().cast()).to_bytes().len();
buf.set_len(len);
buf.shrink_to_fit();
let relative = CStr::from_ptr(relative_path).to_bytes().to_vec();
return Ok((
ManuallyDrop::new(WasiFd::from_raw(fd as u32)),
PathBuf::from(OsString::from_vec(buf)),
PathBuf::from(OsString::from_vec(relative)),
));
}
}