Closed briansmith closed 3 months ago
If we are adding a std
dependency for these targets, should we also move to using std::File
so that we don't even need DropGuard anymore? Also, should use of std
require enabling the "std"
cargo feature?
If we are adding a std dependency for these targets, should we also move to using std::File so that we don't even need DropGuard anymore?
Unless/until we can use std::syc::OnceLock
or a polyfill for it, it doesn't make much sense right not to use std::File
, because we'd end up using std::File::open()
and then immediately calling into_raw_fd()
.
Also, should use of std require enabling the "std" cargo feature?
No. Note that this PR effectively only uses libstd on targets for which we know libstd is already available.
Unless/until we can use std::syc::OnceLock or a polyfill for it, it doesn't make much sense right not to use std::File, because we'd end up using std::File::open() and then immediately calling into_raw_fd().
Well, actually, it is possible to use std::File
in wait_until_rng_ready
now.
In https://github.com/rust-random/getrandom/pull/458, instead of moving wait_until_rng_ready
, I took @josephlr suggestion and replaced DropGuard
with std::fs::File
.
Closing this in favor of #458 based on @newpavlov's comment in the issue.
use_file:
std::sync::Mutex
, dropping all libpthread use.pthreads mutexes are not safe to move. While it is very unlikely that the mutex we create will ever be moved, we don't actively do anything to actively prevent it from being moved. (libstd, when it used/uses pthreads mutexes, would box them to prevent them from being moved.)
Also, now on Linux and Android (and many other targets for which we don't use use_std), libstd uses futexes instead of pthreads mutexes. Thus using libstd's Mutex will be more efficient and avoid adding an often-otherwise-unnecessary libpthreads dependency on these targets.
use_file
.This will not affect our plans for --linux-none, since we don't plan to use
use_file
for it. OnceLockThis breaks 32-bit x86 QNX Neutrino, which doesn't have libstd because the target itself is abandoned [3]. the other QNX Neutrino targets didn't get libstd support until Rust 1.69, so this effectively raises the MSRV for them to 1.69.
Otherwise, the MSRV increases to 1.63 for the above-mentioned targets, as that's when
Mutex::new()
became aconst fn
.I tried to use
Once
to avoid the MSRV increase but it doesn't support fallible initialization even in Nightly.OnceLock
wasn't added until 1.70.On x86_64 Linux, this change removes all libpthreads dependencies:
and adds these libstd dependencies:
as measured using
cargo asm
.[1] https://github.com/rust-lang/rust/blob/c1dba09f263cbff6170f130aa418e28bdf22bd96/library/std/src/sys/sync/mutex/mod.rs#L4-L10 [2] https://github.com/rust-lang/rust/blob/c1dba09f263cbff6170f130aa418e28bdf22bd96/library/std/src/sys/sync/mutex/mod.rs#L17-L20 [3] https://github.com/rust-random/getrandom/issues/453#issuecomment-2148124364