clean up safety docs

src/shared_ptr.rs

@@ -49,14 +49,16 @@ where
     }
 
     /// Create a shared pointer from an already-allocated object
-    /// Corresponds to constructor (3) of [std::shared\_ptr](https://en.cppreference.com/w/cpp/memory/shared_ptr/shared_ptr)
+    /// Corresponds to constructor (3) of [`std::shared_ptr`](https://en.cppreference.com/w/cpp/memory/shared_ptr/shared_ptr)
     ///
-    /// The SharedPtr gains ownership of the pointer and will call std::default_delete on it when the refcount goes to zero.
+    /// The SharedPtr gains ownership of the pointer and will call `std::default_delete` on it when the refcount goes to zero.
     /// The data will not be moved, so any pointers to this data elsewhere in the program continue to be valid
     ///
     /// # Safety
     ///
-    /// Value must either be null or point to a valid instance of T
+    /// * Value must either be null or point to a valid instance of T
+    /// * Value must not be deleted (as the `std::shared_ptr` now manages its lifetime)
+    /// * Value must not be accessed after the last `std::shared_ptr` is dropped
     pub unsafe fn from_unmanaged(value: *mut T) -> Self {
         let mut shared_ptr = MaybeUninit::<SharedPtr<T>>::uninit();
         let new = shared_ptr.as_mut_ptr().cast();

src/unique_ptr.rs

@@ -114,7 +114,7 @@ impl<T> UniquePtr<T>
 where
     T: UniquePtrTarget + SharedPtrTarget,
 {
-    /// Convert this UniquePtr to a SharedPtr, analogous to constructor (13) for [std::shared\_ptr](https://en.cppreference.com/w/cpp/memory/shared_ptr/shared_ptr)
+    /// Convert this UniquePtr to a SharedPtr, analogous to constructor (13) for [`std::shared_ptr`](https://en.cppreference.com/w/cpp/memory/shared_ptr/shared_ptr)
     pub fn to_shared(self) -> SharedPtr<T> {
         unsafe { SharedPtr::from_unmanaged(self.into_raw()) }
     }