From 9bb11ba51135b0398b5a8b9feca24149d96fa5e8 Mon Sep 17 00:00:00 2001 From: Dan Gohman Date: Sat, 17 Jul 2021 12:33:31 -0700 Subject: Remove an unnecessary `Mutex` around argument initialization. In the command-line argument initialization code, remove the Mutex around the `ARGV` and `ARGC` variables, and simply check whether ARGV is non-null before dereferencing it. This way, if either of ARGV or ARGC is not initialized, we'll get an empty argument list. This allows simple cdylibs to avoid having `pthread_mutex_lock`/`pthread_mutex_unlock` appear in their symbol tables if they don't otherwise use threads. --- library/std/src/sys/unix/args.rs | 15 +++++++-------- 1 file changed, 7 insertions(+), 8 deletions(-) (limited to 'library/std/src') diff --git a/library/std/src/sys/unix/args.rs b/library/std/src/sys/unix/args.rs index d9e3c29f36b..a6480199e70 100644 --- a/library/std/src/sys/unix/args.rs +++ b/library/std/src/sys/unix/args.rs @@ -77,16 +77,10 @@ mod imp { use crate::ptr; use crate::sync::atomic::{AtomicIsize, AtomicPtr, Ordering}; - use crate::sys_common::mutex::StaticMutex; - static ARGC: AtomicIsize = AtomicIsize::new(0); static ARGV: AtomicPtr<*const u8> = AtomicPtr::new(ptr::null_mut()); - // We never call `ENV_LOCK.init()`, so it is UB to attempt to - // acquire this mutex reentrantly! - static LOCK: StaticMutex = StaticMutex::new(); unsafe fn really_init(argc: isize, argv: *const *const u8) { - let _guard = LOCK.lock(); ARGC.store(argc, Ordering::Relaxed); ARGV.store(argv as *mut _, Ordering::Relaxed); } @@ -128,9 +122,14 @@ mod imp { fn clone() -> Vec { unsafe { - let _guard = LOCK.lock(); - let argc = ARGC.load(Ordering::Relaxed); + // Load ARGC and ARGV without a lock. If the store to either ARGV or + // ARGC isn't visible yet, we'll return an empty argument list. let argv = ARGV.load(Ordering::Relaxed); + let argc = if argv.is_null() { + 0 + } else { + ARGC.load(Ordering::Relaxed) + }; (0..argc) .map(|i| { let cstr = CStr::from_ptr(*argv.offset(i) as *const libc::c_char); -- cgit 1.4.1-3-g733a5