Merge pull request #566 from Noratrieb/layout-pages-nuclear

Archive most pages in the reference

Author: RalfJung

reference/src/layout/arrays-and-slices.md

@@ -1,43 +1,7 @@
 # Layout of Rust array types and slices
 
-## Layout of Rust array types 
+**This page has been archived**
 
-Array types, `[T; N]`, store `N` values of type `T` with a _stride_ that is
-equal to the size of `T`. Here, _stride_ is the distance between each pair of
-consecutive values within the array.
+It did not actually reflect current layout guarantees and caused frequent confusion.
 
-The _offset_ of the first array element is `0`, that is, a pointer to the array
-and a pointer to its first element both point to the same memory address.
-
-The _alignment_ of array types is greater or equal to the alignment of its
-element type. If the element type is `repr(C)` the layout of the array is
-guaranteed to be the same as the layout of a C array with the same element type.
-
-> **Note**: the type of array arguments in C function signatures, e.g., `void
-> foo(T x[N])`, decays to a pointer. That is, these functions do not take arrays
-> as an arguments, they take a pointer to the first element of the array
-> instead. Array types are therefore _improper C types_ (not C FFI safe) in Rust
-> foreign function declarations, e.g., `extern { fn foo(x: [T; N]) -> [U; M];
-> }`. Pointers to arrays are fine: `extern { fn foo(x: *const [T; N]) -> *const
-> [U; M]; }`, and `struct`s and `union`s containing arrays are also fine.
-
-### Arrays of zero-size
-
-Arrays `[T; N]` have zero size if and only if their count `N` is zero or their
-element type `T` is zero-sized.
-
-### Layout compatibility with packed SIMD vectors
-
-The [layout of packed SIMD vector types][Vector] [^2] requires the _size_ and
-_alignment_ of the vector elements to match. That is, types with [packed SIMD
-vector][Vector] layout are layout compatible with arrays having the same element
-type and the same number of elements as the vector.
-
-[^2]: The [packed SIMD vector][Vector] layout is the layout of `repr(simd)` types like [`__m128`].
-
-[Vector]: packed-simd-vectors.md
-[`__m128`]: https://doc.rust-lang.org/core/arch/x86_64/struct.__m128.html
-
-## Layout of Rust slices
-
-The layout of a slice `[T]` of length `N` is the same as that of a `[T; N]` array. 
+The old content can be accessed [on GitHub](https://github.com/rust-lang/unsafe-code-guidelines/blob/c138499c1de03b908dfe719a41193c84f8146883/reference/src/layout/arrays-and-slices.md).