Auto merge of #72204 - RalfJung:abort, r=Mark-Simulacrum

make abort intrinsic safe, and correct its documentation

Turns out `std::process::abort` is not the same as the intrinsic, the comment was just wrong. Quoting from the unix implementation:
```
// On Unix-like platforms, libc::abort will unregister signal handlers
// including the SIGABRT handler, preventing the abort from being blocked, and
// fclose streams, with the side effect of flushing them so libc buffered
// output will be printed.  Additionally the shell will generally print a more
// understandable error message like "Abort trap" rather than "Illegal
// instruction" that intrinsics::abort would cause, as intrinsics::abort is
// implemented as an illegal instruction.
```

2 files changed, 4 insertions, 0 deletions

diff --git a/src/libstd/sync/mpsc/shared.rs b/src/libstd/sync/mpsc/shared.rs
index fd9d61e99c2..d1a46c51757 100644
--- a/src/libstd/sync/mpsc/shared.rs
+++ b/src/libstd/sync/mpsc/shared.rs
@@ -354,6 +354,8 @@ impl<T> Packet<T> {
 
         // See comments on Arc::clone() on why we do this (for `mem::forget`).
         if old_count > MAX_REFCOUNT {
+            // remove `unsafe` on bootstrap bump
+            #[cfg_attr(not(bootstrap), allow(unused_unsafe))]
             unsafe {
                 abort();
             }
diff --git a/src/libstd/sync/mpsc/sync.rs b/src/libstd/sync/mpsc/sync.rs
index 79123903e92..603764922c5 100644
--- a/src/libstd/sync/mpsc/sync.rs
+++ b/src/libstd/sync/mpsc/sync.rs
@@ -358,6 +358,8 @@ impl<T> Packet<T> {
 
         // See comments on Arc::clone() on why we do this (for `mem::forget`).
         if old_count > MAX_REFCOUNT {
+            // remove `unsafe` on bootstrap bump
+            #[cfg_attr(not(bootstrap), allow(unused_unsafe))]
             unsafe {
                 abort();
             }