Update use of libc::timespec to prepare for future libc version#55
Merged
taiki-e merged 1 commit intosmol-rs:masterfrom Dec 3, 2022
Merged
Update use of libc::timespec to prepare for future libc version#55taiki-e merged 1 commit intosmol-rs:masterfrom
taiki-e merged 1 commit intosmol-rs:masterfrom
Conversation
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
Comment on lines
+266
to
+267
| const TS_ZERO: libc::timespec = | ||
| unsafe { std::mem::transmute([0u8; std::mem::size_of::<libc::timespec>()]) }; |
Collaborator
There was a problem hiding this comment.
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
Member
There was a problem hiding this comment.
I saw that too, is that some kind of compiler magic?
Contributor
Author
There was a problem hiding this comment.
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
Merged
This file contains hidden or bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
Sign up for free
to join this conversation on GitHub.
Already have an account?
Sign in to comment
3 participants
Add this suggestion to a batch that can be applied as a single commit.This suggestion is invalid because no changes were made to the code.Suggestions cannot be applied while the pull request is closed.Suggestions cannot be applied while viewing a subset of changes.Only one suggestion per line can be applied in a batch.Add this suggestion to a batch that can be applied as a single commit.Applying suggestions on deleted lines is not supported.You must change the existing code in this line in order to create a valid suggestion.Outdated suggestions cannot be applied.This suggestion has been applied or marked resolved.Suggestions cannot be applied from pending reviews.Suggestions cannot be applied on multi-line comments.Suggestions cannot be applied while the pull request is queued to merge.Suggestion cannot be applied right now. Please check back later.
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