On 11 May 2017 at 10:20, Serge Sivkov <[email protected]> wrote: > thank for your reply, it allow me partially resolve problem: code works on > x86 without any problems (yet with Gc.compact() calls insert after each line > of code). But ARM version allways raises CallToExpiredClosure on the first > call to callback. > I've tried next variants to store callback if struct field: > - existing toplevel function by name > - store function name to toplevel ref and save it to struct field by > !ref_name > - by register closure to function (fun a b c d -> top_level_function a b c > d) with Ctypes.Root.create > - by store same closure to Hashtbl. > - by register finaliser with Gc.finalise for closure (and it has not been > called) > All this variants work on x86 and do not work on ARM, i.e. first call to > OCaml callback from C raises CallToExpiredClosure. > It seems I don't understand problem at all. > > So here is base questions: > - in case I store in C struct field existing toplevel function by name, may > it be GC'ed?
Yes. The only way to prevent a value from being collected is to ensure that it's visible to the GC, which requires keeping a reference to it in an OCaml object. The GC doesn't scan C memory, such as struct fields, so storing a function in a struct field won't stop it being collected. > -what may cause CallToExpiredClosure raise too if I has only one callback to > call and at C side this struct in GDB seems to be correct? If there's an OCaml reference to the function passed to C then CallToExpiredClosure should never occur. But it has to be exactly the same function -- for example, storing a function in a struct field, then reading from the struct field will create a new copy of the function, which won't prevent the original from being collected. If you have a (smallish) running example somewhere of the code that's causing problems I'd be happy to take a look. Kind regards, Jeremy. _______________________________________________ Ctypes mailing list [email protected] http://lists.ocaml.org/listinfo/ctypes
