Update use of libc::timespec to prepare for future libc version #55
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In a future release of the `libc` crate, `libc::timespec` will contain private padding fields on `*-linux-musl` targets and so the struct will no longer be able to be created using the literal initialization syntax. Update `TS_ZERO` to create a value by initializing an array of the correct size to `0` and then transmuting to `libc::timespec`. Update struct literal use of `libc::timespec` to initialize to `TS_ZERO` and then manually update the appropriate fields. Also updates a raw syscall to use the libc function instead as on musl 1.2, it correctly handles `libc::timespec` values which, in musl 1.2, are always 16 bytes in length regardless of platform.
taiki-e
reviewed
Dec 3, 2022
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| const TS_ZERO: libc::timespec = | ||
| unsafe { std::mem::transmute([0u8; std::mem::size_of::<libc::timespec>()]) }; |
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Hmm, I thought const transmute was stable at 1.56, but it seems to compile successfully at 1.47?
https://doc.rust-lang.org/stable/std/intrinsics/fn.transmute.html
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I saw that too, is that some kind of compiler magic?
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Yeah, I think it was special cased in the compiler for 1.46 and that special casing was removed in 1.56 when reading union fields in const contexts was stabilized.
taiki-e
approved these changes
Dec 3, 2022
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In a future release of the
libccrate,libc::timespecwill contain private padding fields on*-linux-musltargets and so the struct will no longer be able to be created using the literal initialization syntax.Update
TS_ZEROto create a value by initializing an array of the correct size to0and then transmuting tolibc::timespec. Update struct literal use oflibc::timespecto initialize toTS_ZEROand then manually update the appropriate fields. Also updates a raw syscall to use the libc function instead as on musl 1.2, it correctly handleslibc::timespecvalues which, in musl 1.2, are always 16 bytes in length regardless of platform.See also rust-lang/libc#2088