Henry Vermaak schreef op 12 mrt '13:
> On Mon, Mar 11, 2013 at 11:26:57PM +0100, Darius Blaszyk wrote: > >> I'm stuck porting a macro from C. Below is the original define. The part I'm struggeling with is the right most part after the - sign. #define GETNEXT(x) ((LList *)(((char *) x) - ((char *) & (((LList *)0)^.next)))) > > I'm assuming that the "^." should be "->", in which case the last bit is > doing the same as the offsetof() macro. So the macro is subtracting the > offset in bytes of the "next" member of the LList struct from x, then > casting it to (LList *). > > I'd wager that the GETNEXT() isn't actually doing what it says, but > something more like container_of() (because it's _subtracting_ the > offset). I may be wrong, though, do you have an example of its usage? > > Henry > _______________________________________________ > fpc-pascal maillist - fpc-pascal@lists.freepascal.org > http://lists.freepascal.org/mailman/listinfo/fpc-pascal [1] I will let your email sink in later, but here is a usage example as requested if (list->next) GETNEXT(list->prev)->nextname = GETNEXT(list->next)->name; else GETNEXT(list->prev)->nextname = 0; Both name and nextname are pchar's. Regards, Darius Links: ------ [1] http://lists.freepascal.org/mailman/listinfo/fpc-pascal
_______________________________________________ fpc-pascal maillist - fpc-pascal@lists.freepascal.org http://lists.freepascal.org/mailman/listinfo/fpc-pascal
