On Thu 11 Sep 2008 23:06, "Neil Jerram" <[EMAIL PROTECTED]> writes:
>> Classes that are not metaclasses allocate their instances using "light >> structs". So the object layout goes like this: >> >> the vtable word the data word >> +-------------------------------+---------------------+ >> SCM of object = |SCM of class | scm_tc3_struct | SCM* array of slots | >> +-------------------------------|---------------------+ >> >> For classes, the SCM* points to the middle of a SCM array, which has >> some number of words before 0; 4 words normally, or 6 if the object is >> an "entity", like a generic function. But for objects there are no words >> before 0, hence the valid valgrind error. > > Are you sure? Surely that would require a call somewhere to > scm_alloc_struct() with n_extra = 0, and I can't see any of those. I'm sure -- goops.c:1541 in master. Doesn't go through scm_alloc_struct at all. > Also, is Mikael right with his error #1? I'm thinking not, because I > believe that instances are structs too, so surely it's OK to call > SCM_STRUCT_DATA (x)[...] on them? I can't recall the mail at the moment. Please reply if you want me to dig through this -- I'm happy to do so. But instances are structs, yes. Calling SCM_STRUCT_DATA (x)[] does work. You have to know how many fields there are, though -- you get that from the vtable. Andy -- http://wingolog.org/
