Boost C++ Libraries of the most highly regarded and expertly designed C++ library projects in the world. Herb Sutter and Andrei Alexandrescu, C++ Coding Standards

This is the documentation for an old version of Boost. Click here to view this page for the latest version.

Stack allocation

Class stack_allocator
Class stack_context
Segmented stacks

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, sctx is a stack_context, and size is a std::size_t:


return type


a.allocate( sctx, size)


creates a stack of at least size bytes and stores both values in sctx

a.deallocate( sctx)


deallocates the stack created by a.allocate()

[Important] 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] Important

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

[Note] Note

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

[Note] 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).