If Boost.Context uses fcontext_t (the default) as its implementation, it must be built for the particular compiler(s) and CPU architecture(s) being targeted. Using fcontext_t, Boost.Context includes assembly code and, therefore, requires GNU as and GNU preprocessor for supported POSIX systems, MASM for Windows/x86 systems and ARMasm for Windows/arm systems.
MASM64 (ml64.exe) is a part of Microsoft's Windows Driver Kit.
Please note that
For cross-compiling the lib you must specify certain additional properties
at bjam command line:
Windows using fcontext_t: for safe SEH the property 'asmflags=\safeseh' must be specified at bjam command line.
Windows using fcontext_t: turn off global program optimization (/GL) and change /EHsc (compiler assumes that functions declared as extern "C" never throw a C++ exception) to /EHs (tells compiler assumes that functions declared as extern "C" may throw an exception).