[m-dev.] Re: type_info bug fix

[Tyson Richard DOWD]

> 
> I think the code would be clearer if you implement the above macros
> by actually defining a C struct for the types, and just casting the
> argument to a pointer to this struct.

Yep.

> It is a little bit tricky in the case of structs with two variable
> sized bits, i.e. type_layout, but I think it would help even for
> those cases.

Nope, type_layouts are as large as the number of tags we use (fixed
size), the things type_layouts point to only ever have one variable sized 
part.  And we can move that to the end.  In fact, I think I will, so
your approach will work quite nicely, and if we ever need two variable
size parts... we know it can be done.

> It might perhaps be better to require a cast to MR_TypeLayout in the caller
> rather than casting the argument to MR_TypeLayout_part1 in the macros --
> I'm not sure whether it is better to have the cast in the macros or in
> the caller.

There are arguments for both - you can get some typechecking if you do
it in the caller, since you can cast the results... Hmmm... with some
use of unions, it would probably work out nicely.

-- 
       Tyson Dowd           # "Most people's C code should be indented
                            #  six feet downward and covered with 
     trd at cs.mu.oz.au        #  dirt."
http://www.cs.mu.oz.au/~trd # - Blair Houghton, on C code indentation