libboost-context1.71.0 1.71.0-5ubuntu1 (i386 binary) in ubuntu focal

 This package forms part of the Boost C++ Libraries collection.
 .
 Boost.Context is a foundational library that provides a sort of
 cooperative multitasking on a single thread. By providing an
 abstraction of the current execution state in the current thread,
 including the stack (with local variables) and stack pointer, all
 registers and CPU flags, and the instruction pointer, a fcontext_t
 instance represents a specific point in the application's execution
 path. This is useful for building higher-level abstractions, like
 coroutines, cooperative threads (userland threads) or an equivalent
 to C# keyword yield in C++.