Auto merge of #70747 - Centril:rollup-2vx9bve, r=Centril

Rollup of 9 pull requests

Successful merges:

 - #69860 (Use associated numeric consts in documentation)
 - #70576 (Update the description of the ticket to point at RFC 1721)
 - #70597 (Fix double-free and undefined behaviour in libstd::syn::unix::Thread::new)
 - #70640 (Hide `task_context` when lowering body)
 - #70641 (Remove duplicated code in trait selection)
 - #70707 (Remove unused graphviz emitter)
 - #70720 (Place TLS initializers with relocations in .tdata)
 - #70735 (Clean up E0502 explanation)
 - #70741 (Add test for #59023)

Failed merges:

r? @ghost

2 files changed, 10 insertions, 17 deletions

diff --git a/src/libstd/sys/hermit/stack_overflow.rs b/src/libstd/sys/hermit/stack_overflow.rs
index 65a1b17acce..121fe42011d 100644
--- a/src/libstd/sys/hermit/stack_overflow.rs
+++ b/src/libstd/sys/hermit/stack_overflow.rs
@@ -1,11 +1,3 @@
-pub struct Handler;
-
-impl Handler {
-    pub unsafe fn new() -> Handler {
-        Handler
-    }
-}
-
 #[inline]
 pub unsafe fn init() {}
 
diff --git a/src/libstd/sys/hermit/thread.rs b/src/libstd/sys/hermit/thread.rs
index c3c29c93826..c7bea168f34 100644
--- a/src/libstd/sys/hermit/thread.rs
+++ b/src/libstd/sys/hermit/thread.rs
@@ -8,8 +8,6 @@ use crate::sys::hermit::abi;
 use crate::time::Duration;
 use core::u32;
 
-use crate::sys_common::thread::*;
-
 pub type Tid = abi::Tid;
 
 /// Priority of a task
@@ -49,26 +47,29 @@ impl Thread {
         p: Box<dyn FnOnce()>,
         core_id: isize,
     ) -> io::Result<Thread> {
-        let p = box p;
+        let p = Box::into_raw(box p);
         let mut tid: Tid = u32::MAX;
         let ret = abi::spawn(
             &mut tid as *mut Tid,
             thread_start,
-            &*p as *const _ as *const u8 as usize,
+            p as usize,
             Priority::into(NORMAL_PRIO),
             core_id,
         );
 
-        return if ret == 0 {
-            mem::forget(p); // ownership passed to pthread_create
-            Ok(Thread { tid: tid })
-        } else {
+        return if ret != 0 {
+            // The thread failed to start and as a result p was not consumed. Therefore, it is
+            // safe to reconstruct the box so that it gets deallocated.
+            drop(Box::from_raw(p));
             Err(io::Error::new(io::ErrorKind::Other, "Unable to create thread!"))
+        } else {
+            Ok(Thread { tid: tid })
         };
 
         extern "C" fn thread_start(main: usize) {
             unsafe {
-                start_thread(main as *mut u8);
+                // Finally, let's run some code.
+                Box::from_raw(main as *mut Box<dyn FnOnce()>)();
             }
         }
     }