add links to interesting items in std::ptr documentation

r? @steveklabnik

add links for Box, Rc, and Vec

src/libcore/intrinsics.rs

@@ -224,15 +224,20 @@ extern "rust-intrinsic" {
     ///   trait objects, because they can't be read out onto the stack and
     ///   dropped normally.
     ///
-    /// * It is friendlier to the optimizer to do this over `ptr::read` when
-    ///   dropping manually allocated memory (e.g. when writing Box/Rc/Vec),
-    ///   as the compiler doesn't need to prove that it's sound to elide the
-    ///   copy.
+    /// * It is friendlier to the optimizer to do this over [`ptr::read`] when
+    ///   dropping manually allocated memory (e.g. when writing
+    ///   [`Box`]/[`Rc`]/[`Vec`]), as the compiler doesn't need to prove that
+    ///   it's sound to elide the copy.
     ///
     /// # Undefined Behavior
     ///
-    /// This has all the same safety problems as `ptr::read` with respect to
+    /// This has all the same safety problems as [`ptr::read`] with respect to
     /// invalid pointers, types, and double drops.
+    ///
+    /// [`ptr::read`]: fn.read.html
+    /// [`Box`]: ../boxed/struct.Box.html
+    /// [`Rc`]: ../rc/struct.Rc.html
+    /// [`Vec`]: ../vec/struct.Vec.html
     #[stable(feature = "drop_in_place", since = "1.8.0")]
     pub fn drop_in_place<T: ?Sized>(to_drop: *mut T);
 

src/libcore/ptr.rs

@@ -114,11 +114,17 @@ pub unsafe fn replace<T>(dest: *mut T, mut src: T) -> T {
 /// # Safety
 ///
 /// Beyond accepting a raw pointer, this is unsafe because it semantically
-/// moves the value out of `src` without preventing further usage of `src`.
-/// If `T` is not `Copy`, then care must be taken to ensure that the value at
-/// `src` is not used before the data is overwritten again (e.g. with `write`,
-/// `zero_memory`, or `copy_memory`). Note that `*src = foo` counts as a use
-/// because it will attempt to drop the value previously at `*src`.
+/// moves the value out of `src` without preventing further usage of `src`. If
+/// `T` is not [`Copy`], then care must be taken to ensure that the value at
+/// `src` is not used before the data is overwritten again (e.g. with
+/// [`write`], [`zero_memory`], or [`copy_memory`]). Note that `*src = foo`
+/// counts as a use because it will attempt to drop the value previously at
+/// `*src`.
+///
+/// [`Copy`]: ../marker/trait.Copy.html
+/// [`write`]: fn.write.html
+/// [`zero_memory`]: fn.zero_memory.html
+/// [`copy_memory`]: fn.copy_memory.html
 ///
 /// # Examples
 ///
@@ -206,11 +212,17 @@ pub unsafe fn write<T>(dst: *mut T, src: T) {
 /// # Safety
 ///
 /// Beyond accepting a raw pointer, this is unsafe because it semantically
-/// moves the value out of `src` without preventing further usage of `src`.
-/// If `T` is not `Copy`, then care must be taken to ensure that the value at
-/// `src` is not used before the data is overwritten again (e.g. with `write`,
-/// `zero_memory`, or `copy_memory`). Note that `*src = foo` counts as a use
-/// because it will attempt to drop the value previously at `*src`.
+/// moves the value out of `src` without preventing further usage of `src`. If
+/// `T` is not [`Copy`], then care must be taken to ensure that the value at
+/// `src` is not used before the data is overwritten again (e.g. with
+/// [`write`], [`zero_memory`], or [`copy_memory`]). Note that `*src = foo`
+/// counts as a use because it will attempt to drop the value previously at
+/// `*src`.
+///
+/// [`Copy`]: ../marker/trait.Copy.html
+/// [`write`]: fn.write.html
+/// [`zero_memory`]: fn.zero_memory.html
+/// [`copy_memory`]: fn.copy_memory.html
 ///
 /// # Examples
 ///