Controlling and querying object alignment

C++11 provides standardized methods for specifying and querying the alignment requirements of a type (something that was previously possible only through compiler-specific methods). Controlling the alignment is important in order to boost performance on different processors and enable the use of some instructions that only work with data on particular alignments.

For example, Intel Streaming SIMD Extensions (SSE) and Intel SSE2, which are a set of processor instructions that can greatly increase performance when the same operations are to be applied on multiple data objects, require 16 bytes of alignment of data. On the other hand, for Intel Advanced Vector Extensions (or Intel AVX), which expands most integer processor commands to 256 bits, it is highly recommended to use 32 bytes alignment. This recipe explores the alignas specifier for controlling the alignment requirements and the alignof operator, which retrieves the...