Hi,

The problem had been discussed here:

But it's still not clear how to set the stack pointer portably, even after examining the code of Boost.Coroutine. For now, Boost.Context only supports downward stack, and Boost.Coroutine, which happened to be written by the same author, just assumes that the stack always grows downward, which is not really a portable implementation, if future Boost.Context supports upward stack, Boost.Coroutine has to be changed as well.

Even than that, what does "beginning of the stack" really means?

Why the beginning of a downward stack is [s+3], not [s+2]?

If it's a upward stack, is beginning [s] or [s-1]?