On Mon, Mar 28, 2011 at 3:14 PM, Oliver Kowalke <oliver.kowalke@gmx.de> wrote:
Hello Giovanni,
thank you for your review (and of course all others) - it really helps to get the lib shaped (I got very view responses before the review).
I've started to modify the lib (you can take a look at git://gitorious.org/boost-dev/boost-dev.git, branch context-dev) in order to address the issues raised by the review. If I believe all issues are addressed we can start a mini-review (or I'll send you and the other reviews an eMail for checking the new variant for discussion).
Re mail: yes please. I'm taking a look at the code and I see you are doing quite a bit of changes. I couple of initial comments: - remember that all extern "C" functions are not really in the boost::contexts::details namespace, so you should really add a unique prefix to them (boost_context_* for example) - To support stateful functors you are using std::function that imply a certain overhead. Why not use something like this: assuming you have a C like make_context(context_impl*, void (*f)(void *)), change your trampoline function to something like this: template<class T> struct jump { T& x; context_impl *src, *dest; }; template<typename T> void trampoline(void * parm) { jump<T> & jmp = *static_cast<jump*>(parm); T x = jmp.x; swap_context(jmp.src, jmp.dest); x(); } now in context constructor: template<class T> context(T f) { context_impl temp_context; jump<T> p (f, &m_context, &temp_context); make_context(my_context, &trampoline<T>, &p); swap_context(&temp_context, &m_context); // here be magic } T has now been copied in at the bottom of the stack controlled by m_context. This requires a context switch in the constructor to copy T immediately, but it will probably cost less than constructing an std::funciton. Note that if you control the context_impl implementation and the associated make/swap context, you do not really need to invoke the trampoline function to do the copy, but you can carefully set-up the stack as if it had been done. A similar trick can be used to save a dynamic allocation of context_impl (for the ucontext_ case) or to make it an opaque type. HTH, -- gpd