as_ptr returns a read-only pointer

2 files changed, 11 insertions, 0 deletions

diff --git a/src/libcore/slice/mod.rs b/src/libcore/slice/mod.rs
index 8731f486753..c273153fa5e 100644
--- a/src/libcore/slice/mod.rs
+++ b/src/libcore/slice/mod.rs
@@ -359,6 +359,10 @@ impl<T> [T] {
     /// The caller must ensure that the slice outlives the pointer this
     /// function returns, or else it will end up pointing to garbage.
     ///
+    /// The caller must also ensure that the memory the pointer (non-transitively) points to
+    /// is never written to (except inside an `UnsafeCell`). If you need to mutate
+    /// the contents of the slice, use [`as_mut_ptr`].
+    ///
     /// Modifying the container referenced by this slice may cause its buffer
     /// to be reallocated, which would also make any pointers to it invalid.
     ///
@@ -374,6 +378,8 @@ impl<T> [T] {
     ///     }
     /// }
     /// ```
+    ///
+    /// [`as_mut_ptr`]: #method.as_mut_ptr
     #[stable(feature = "rust1", since = "1.0.0")]
     #[inline]
     pub const fn as_ptr(&self) -> *const T {
diff --git a/src/libcore/str/mod.rs b/src/libcore/str/mod.rs
index 45421848cec..96a5ce61ca0 100644
--- a/src/libcore/str/mod.rs
+++ b/src/libcore/str/mod.rs
@@ -2188,7 +2188,12 @@ impl str {
     /// [`u8`]. This pointer will be pointing to the first byte of the string
     /// slice.
     ///
+    /// The caller must ensure that the memory the pointer points to
+    /// is never written to. If you need to mutate
+    /// the contents of the string slice, use [`as_mut_ptr`].
+    ///
     /// [`u8`]: primitive.u8.html
+    /// [`as_mut_ptr`]: #method.as_mut_ptr
     ///
     /// # Examples
     ///