I did not read your question properly, sorry! Thanks for the clarification, I didn't know foreign-lambda were the one that had to do the CPS-conversion. Does that mean there is a small performance overhead when using foreign-lambda as opposed to just foreign-primitive?
K. On Thu, Jun 6, 2013 at 11:59 AM, Thomas Chust <ch...@web.de> wrote: > On 2013-06-06 11:46, Kristian Lein-Mathisen wrote: > > [...] > > From what I understand, this is exactly what foreign-primitive does: > > wraps C_return in a CPS, keeping the stack-allocation alive. > > [...] > > Hello, > > well, kind of. > > Since compiled CHICKEN code is fully CPS transformed you don't wrap > something in a CPS context, you wrap anything that isn't natively in CPS > with a function that calls it and passes the result to the values > continuation. > > foreign-lambda and friends create such wrappers, foreign-primitive > doesn't create a wrapper, it just expects the code to be in CPS style, > which means that the code may never return at all. C_return is, in that > case, just syntactic sugar for invoking the values continuation. > > Since the code in a foreign-primitive never returns, things allocated in > the nursery (ie. on the stack) live on "forever", or rather until the > next minor garbage collection comes around, transfers anything that's > still referenced into the second generation heap and throws away the > nursery (ie. almost the entire stack). > > Therefore foreign-primitive can do allocation in the nursery, but > foreign-lambda can't. However, foreign-lambda could still allocate > directly in the second generation heap or transfer nursery-allocated > values directly into the heap upon return before the stack context is > destroyed. The question is whether such magic is present for > foreign-safe-lambda, as the documentation may indicate, or whether that > is not the case, as Felix has indicated with his earlier message :-) > > Ciao, > Thomas > > > -- > When C++ is your hammer, every problem looks like your thumb. > >
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