Merge pull request #2205 from joshlf/patch-11

Guarantee size and alignment of more integer primitives

Author: traviscross

src/type-layout.md

@@ -48,9 +48,12 @@ r[layout.primitive.size-minimum]
 r[layout.primitive.size-align]
 `usize` and `isize` have the same size and alignment.
 
-r[layout.primitive.align]
+r[layout.primitive.platform-specific-alignment]
 The alignment of primitives is platform-specific. In most cases, their alignment is equal to their size, but it may be less. In particular, `i128` and `u128` are often aligned to 4 or 8 bytes even though their size is 16, and on many 32-bit platforms, `i64`, `u64`, and `f64` are only aligned to 4 bytes, not 8.
 
+r[layout.primitive.integer-alignment]
+Alignment is guaranteed to be the same for fixed-width signed and unsigned integer variants of the same indicated size --- that is, for a given size `N`, `align_of::<uN>() == align_of::<iN>()`.
+
 r[layout.pointer]
 ## Pointers and references layout