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## Rationale

#### Dynamic allocation

C++11 added the ability to specify increased alignment (over-alignment) for class types. Unfortunately, `::operator new` allocation functions, `new` expressions and the Default Allocator, `std::allocator`, do not support dynamic memory allocation of over-aligned data. This library provides allocation functions and allocators that respect the alignment requirements of a type and so are suitable for allocating memory for over-aligned types.

`aligned_alloc(alignment, size)`

  Replaces `::operator new(size, std::nothrow)`

`aligned_free(pointer)`

  Replaces `::operator delete(pointer, std::nothrow)`

`aligned_allocator<T>`

  Replaces `std::allocator<T>`

`aligned_allocator_adaptor<Allocator>`

  Replaces use of Allocator

`aligned_delete`

  Replaces `std::default_delete<T>`

#### Pointer alignment

C++11 provided `std::align` in the standard library to align a pointer value. Unfortunately some C++ standard library implementations do not support it yet (libstdc++ as far as gcc 4.8.0) and other standard library implementations implement it incorrectly (dinkumware in msvc11.0). This library provides it for those implementations and also for C++03 compilers where it is equally useful.

#### Querying alignment

C++11 provided the `std::alignment_of` trait in the standard library to query the alignment requirement of a type. Unfortunately some C++ standard library vendors do not implement it in an entirely standard conforming manner, such as for array types (libc++ as far as clang 3.4). Other vendor implementations report incorrect values for certain types, such as pointer to members (msvc 14.0). This library provides it for those implementations and also for C++03 compilers where it is equally useful.

#### Hinting alignment

Allocating aligned memory is sometimes not enough to ensure that optimal code is generated. Developers use specific compiler intrinsics to notify the compiler of a given alignment property of a memory block. This library provides a macro, `BOOST_ALIGN_ASSUME_ALIGNED`, to abstract that functionality for compilers with the appropriate intrinsics.

#### Checking alignment

This library provides a function, `is_aligned` to test the alignment of a pointer value. It is generally useful in assertions to validate that memory is correctly aligned.