Boost C++ Libraries

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Stack allocation

Class stack_allocator

A coroutine uses internally a context which manages a set of registers and a stack. The memory used by the stack is allocated/deallocated via a stack-allocator which is required to model a stack-allocator concept.

stack-allocator concept

A stack-allocator must satisfy the stack-allocator concept requirements shown in the following table, in which a is an object of a stack-allocator type, p is a void *, and s is a std::size_t:

expression	return type	notes
`a.allocate( s)`	`void *`	returns a pointer to `s` bytes allocated from the stack
`a.deallocate( p, s)`	`void`	deallocates `s` bytes of memory beginning at `p`, a pointer previously returned by `a.allocate()`

	Important
	The implementation of `allocate()` might include logic to protect against exceeding the context's available stack size rather than leaving it as undefined behaviour.

	Important
	Calling `deallocate()` with a pointer not returned by `allocate()` results in undefined behaviour.

	Note
	The stack is not required to be aligned; alignment takes place inside coroutine.

	Note
	Depending on the architecture `allocate()` returns an address from the top of the stack (growing downwards) or the bottom of the stack (growing upwards).