Am 29.07.2010 10:36, schrieb Anthony Williams:
Oliver Kowalke<k-oli@gmx.de> writes:
Am 28.07.2010 19:21, schrieb Hartmut Kaiser:
The TIB is not changed (only the pointers pointing to the limit and base of the stack).
That will result in problems, I'm sure - at least as soon as you start moving context's between threads. Could you describe a scenario which will trigger an error, please?
Anything that uses thread-local variables or fiber-local variables will fail if you just run it on another thread or fiber. This can include C runtime functions --- errno is typically thread-local, for example.
OK - it's up to the user anyway. Using thread-local-storage in different threads is always false and boost.context hasn't take special care.
AFAIK migrating Win32 Fibers between threads is not possible and cloning also not - but maybe I'm wrong in this point.
Moving Windows fibers between threads is definitely possible.
Or do I have to use a special function form the Win32 API?
You need 3 fibers to move a fiber between threads:
Thread A is running Fiber 1. It switches to Fiber 2. Thread B is running Fiber 3. It switches to Fiber 1.
Hey presto, fiber 1 has switched threads.
So SwitchToFiber() takes care of TIB (setting the members accordingly). AFAIK only SEH frame, top of stack, current bottom of stack - thats's what boost.context does.
All is now well, provided code on Fiber 1 doesn't use thread-local variables. Recent versions of the MSVC runtime use fiber-local variables instead of thread-local ones, so standard C and C++ functions should be OK,
Hmm - maybe boost.context should take care of fiber data (fs:[0x10]) and arbitary data slot (fs:[0x14])?! Oliver