Re: Interfacing Ada to C

[dewar@merv.cs.nyu.edu (Robert Dewar)]

Bob Duff said

<<Agreed that Pack shouldn't be used for interfacing purposes.  But you
don't always need to use record rep_clauses -- you can often use pragma
Convention(C or whatever) instead.  Record rep clauses are a pain during
maintenance -- they (over)specify all those bit numbers, when all you
really want to say is, "Do it like the corresponding C struct", or "lay
it out in order, using sensible alignment considerations."
>>

In GNAT, it is well defined that a packed record with Convention C has
identical layout to the corresponding C type in which each field has the
length in bits coresponding to the size of the Ada type, we have found
this quite useful.