Rollup merge of #139711 - thaliaarchi:hermit-args, r=jhpratt

Hermit: Unify `std::env::args` with Unix

The only differences between these implementations of `std::env::args` are that Unix uses relaxed ordering, but Hermit uses acquire/release, and Unix truncates `argv` at the first null pointer, but Hermit doesn't. Since Hermit aims for Unix compatibility, unify it with Unix.

The atomic orderings were established in https://github.com/rust-lang/rust/pull/74006 (cc `@euclio)` for Unix and https://github.com/rust-lang/rust/pull/100579 (cc `@joboet)` for Hermit and, before those, they used mutexes and non-atomic statics. I think the difference in orderings is simply from them being changed at different times. The commented explanation for using acquire/release for Hermit is “to broadcast writes by the OS”. I'm not experienced enough with atomics to accurately judge, but I think acquire/release is stronger than needed. Either way, they should match.

Truncating at the first null pointer seems desirable, though I don't know whether it is necessary in practice on Hermit.

cc `@mkroening` `@stlankes` for Hermit

library/std/src/sys/args/hermit.rs

@@ -1,35 +0,0 @@
-use crate::ffi::{CStr, OsString, c_char};
-use crate::os::hermit::ffi::OsStringExt;
-use crate::ptr;
-use crate::sync::atomic::Ordering::{Acquire, Relaxed, Release};
-use crate::sync::atomic::{AtomicIsize, AtomicPtr};
-
-#[path = "common.rs"]
-mod common;
-pub use common::Args;
-
-static ARGC: AtomicIsize = AtomicIsize::new(0);
-static ARGV: AtomicPtr<*const u8> = AtomicPtr::new(ptr::null_mut());
-
-/// One-time global initialization.
-pub unsafe fn init(argc: isize, argv: *const *const u8) {
-    ARGC.store(argc, Relaxed);
-    // Use release ordering here to broadcast writes by the OS.
-    ARGV.store(argv as *mut *const u8, Release);
-}
-
-/// Returns the command line arguments
-pub fn args() -> Args {
-    // Synchronize with the store above.
-    let argv = ARGV.load(Acquire);
-    // If argv has not been initialized yet, do not return any arguments.
-    let argc = if argv.is_null() { 0 } else { ARGC.load(Relaxed) };
-    let args: Vec<OsString> = (0..argc)
-        .map(|i| unsafe {
-            let cstr = CStr::from_ptr(*argv.offset(i) as *const c_char);
-            OsStringExt::from_vec(cstr.to_bytes().to_vec())
-        })
-        .collect();
-
-    Args::new(args)
-}

library/std/src/sys/args/mod.rs

@@ -3,15 +3,15 @@
 #![forbid(unsafe_op_in_unsafe_fn)]
 
 cfg_if::cfg_if! {
-    if #[cfg(all(target_family = "unix", not(any(target_os = "espidf", target_os = "vita"))))] {
+    if #[cfg(any(
+        all(target_family = "unix", not(any(target_os = "espidf", target_os = "vita"))),
+        target_os = "hermit",
+    ))] {
         mod unix;
         pub use unix::*;
     } else if #[cfg(target_family = "windows")] {
         mod windows;
         pub use windows::*;
-    } else if #[cfg(target_os = "hermit")] {
-        mod hermit;
-        pub use hermit::*;
     } else if #[cfg(all(target_vendor = "fortanix", target_env = "sgx"))] {
         mod sgx;
         pub use sgx::*;

library/std/src/sys/args/unix.rs

@@ -6,6 +6,9 @@
 #![allow(dead_code)] // runtime init functions not used during testing
 
 use crate::ffi::CStr;
+#[cfg(target_os = "hermit")]
+use crate::os::hermit::ffi::OsStringExt;
+#[cfg(not(target_os = "hermit"))]
 use crate::os::unix::ffi::OsStringExt;
 
 #[path = "common.rs"]
@@ -73,6 +76,7 @@ pub fn args() -> Args {
     target_os = "illumos",
     target_os = "emscripten",
     target_os = "haiku",
+    target_os = "hermit",
     target_os = "l4re",
     target_os = "fuchsia",
     target_os = "redox",
@@ -100,7 +104,7 @@ mod imp {
 
     unsafe fn really_init(argc: isize, argv: *const *const u8) {
         // These don't need to be ordered with each other or other stores,
-        // because they only hold the unmodified system-provide argv/argc.
+        // because they only hold the unmodified system-provided argv/argc.
         ARGC.store(argc, Ordering::Relaxed);
         ARGV.store(argv as *mut _, Ordering::Relaxed);
     }