Auto merge of #137900 - matthiaskrgr:rollup-rvan5ao, r=matthiaskrgr

Rollup of 10 pull requests

Successful merges:

 - #137375 (Minor internal comments fix for `BufRead::read_line`)
 - #137641 (More precisely document `Global::deallocate()`'s safety.)
 - #137755 (doc: update Wasmtime flags)
 - #137851 (improve `simd_select` error message when used with invalid mask type)
 - #137860 (rustc_target: Add msync target feature and enable it on powerpcspe targets)
 - #137871 (fix `RangeBounds::is_empty` documentation)
 - #137873 (Disable `f16` on Aarch64 without `neon`)
 - #137876 (Adjust triagebot.toml entries for `rustc_mir_build/src/builder/`)
 - #137883 (edit mailmap)
 - #137886 (`name()` and `trimmed_name()` for `stable_mir::crate_def::DefId`)

r? `@ghost`
`@rustbot` modify labels: rollup

1 files changed, 8 insertions, 2 deletions

diff --git a/library/alloc/src/alloc.rs b/library/alloc/src/alloc.rs
index e686a02f29b..3bfdc68dcda 100644
--- a/library/alloc/src/alloc.rs
+++ b/library/alloc/src/alloc.rs
@@ -264,8 +264,14 @@ unsafe impl Allocator for Global {
     #[cfg_attr(miri, track_caller)] // even without panics, this helps for Miri backtraces
     unsafe fn deallocate(&self, ptr: NonNull<u8>, layout: Layout) {
         if layout.size() != 0 {
-            // SAFETY: `layout` is non-zero in size,
-            // other conditions must be upheld by the caller
+            // SAFETY:
+            // * We have checked that `layout` is non-zero in size.
+            // * The caller is obligated to provide a layout that "fits", and in this case,
+            //   "fit" always means a layout that is equal to the original, because our
+            //   `allocate()`, `grow()`, and `shrink()` implementations never returns a larger
+            //   allocation than requested.
+            // * Other conditions must be upheld by the caller, as per `Allocator::deallocate()`'s
+            //   safety documentation.
             unsafe { dealloc(ptr.as_ptr(), layout) }
         }
     }