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

Am 29.03.2011 08:09, schrieb Vicente BOTET:

Please post here all the modification you want to apply to the library so people can make comments without been forced to see you private repository.

modifications: done: - context moveable - context simple class/not a template - context doesn't manage the stack (done) -> user has to safe pair of context and stack - SSE2 control word preserved in i386 asm too - bool context::finished() const indicates if context finished (context is unwound) - function associated with context stored on top of the stack - thx do GIovanni - function pointer or function-object can be used with context todo: - re-factoring C-API: boost_fcontext_make(), boost_fcontext_jump() - test-app for UNIX signals + boost::context - support for stack-unwinding using DWARF facilities (eh_frame) -> investigation if possible regarding to stack unwinding: the user has the possibility to check if the function called by context has finished (stack was cleaned up). The user can decide what to do - throw stack away, do some sophisticated work (jump back into stack and throw exception) or if possible and implementable use a unwind() function using DWARF facilities (eh_frame) to unwind the stack. Oliver