1.5.7 Notes on C type macros

The C-FFI's C interface description language does not model all of the ways of defining new types in C, but all C types should be expressible in it. As a simplification, we do not support anonymous base types in the C interface description language. If a structure or union field has an in-line type definition in C, that definition must be extracted and given a name in order for it to be used. For example, the following C struct

struct something { 
  char *name; 
  long flags; 
  union { 
   long int_val; 
   char *string_val; 
  } val; 
}

can be described with these definitions:

define C-union <anonymous-union-1>
  slot int-val    :: <C-long>;
  slot string-val :: <C-string>;
end C-union;

define C-struct <anonymous-struct-1>
  slot name  :: <C-string>; 
  slot flags :: <C-long>;
  slot val   :: <anonymous-union-1>;
end C-struct;

The slots of these ex-inline types must be accessed through a chain of accesses, for example o.val.string-val.

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C FFI and Win 32 Reference - 31 MAR 2000