Add safety comment to StableAddress impl for Mmap

rust-lang · Apr 3, 2021 · bda6d1f · bda6d1f
1 parent 5773e51
commit bda6d1f
Showing 1 changed file with 4 additions and 0 deletions.
diff --git a/compiler/rustc_data_structures/src/memmap.rs b/compiler/rustc_data_structures/src/memmap.rs
@@ -40,4 +40,8 @@ impl Deref for Mmap {
     }
 }
 
+// SAFETY: On architectures other than WASM, mmap is used as backing storage. The address of this
+// memory map is stable. On WASM, `Vec<u8>` is used as backing storage. The `Mmap` type doesn't
+// export any function that can cause the `Vec` to be re-allocated. As such the address of the
+// bytes inside this `Vec` is stable.
 unsafe impl StableAddress for Mmap {}