actually, reentrant uninitialized mutex acquisition is outright UB

2 files changed, 4 insertions, 6 deletions

diff --git a/src/libstd/sys/unix/args.rs b/src/libstd/sys/unix/args.rs
index c91bd5b22af..220bd11b1f1 100644
--- a/src/libstd/sys/unix/args.rs
+++ b/src/libstd/sys/unix/args.rs
@@ -80,9 +80,8 @@ mod imp {
 
     static mut ARGC: isize = 0;
     static mut ARGV: *const *const u8 = ptr::null();
-    // `ENV_LOCK` is never initialized fully, so this mutex is reentrant!
-    // Do not use it in a way that might be reentrant, that could lead to
-    // aliasing `&mut`.
+    // `ENV_LOCK` is never initialized fully, so it is UB to attempt to
+    // acquire this mutex reentrantly!
     static LOCK: Mutex = Mutex::new();
 
     pub unsafe fn init(argc: isize, argv: *const *const u8) {
diff --git a/src/libstd/sys/unix/os.rs b/src/libstd/sys/unix/os.rs
index 6ef9502ba62..3d98b2efdf1 100644
--- a/src/libstd/sys/unix/os.rs
+++ b/src/libstd/sys/unix/os.rs
@@ -33,9 +33,8 @@ use sys::fd;
 use vec;
 
 const TMPBUF_SZ: usize = 128;
-// `ENV_LOCK` is never initialized fully, so this mutex is reentrant!
-// Do not use it in a way that might be reentrant, that could lead to
-// aliasing `&mut`.
+// `ENV_LOCK` is never initialized fully, so it is UB to attempt to
+// acquire this mutex reentrantly!
 static ENV_LOCK: Mutex = Mutex::new();