Earlier quoted context omitted.
> If an application uses two libraries, each of which handles lists of int, each library will have to independently macro-generate its separate list implementation, and because C's type system is nominal, the generated types will be isomorphic but incompatible. Um, what? C89, 3.1.2.6: "Moreover, two structure, union, or enumeration types declared in separate translation units are compatible if they have the same numb…
> as long as the struct tags are the same Exactly. Now you have a naming problem. You need a naming convention that every user of the list library must follow, or else their types will be incompatible. And what about typedefs? If A is a typedef of B, or more generally A and B are typedef-related (their normal forms, obtained by following all typedefs, are the same), lists of A and B will be incompatible unless users…
Oh, that's simple: just have empty struct tags.
> And what about typedefs?
The names introduced by the typedefs are irrelevant.
> A and B are typedef-related (their normal forms, obtained by following all typedefs, are the same), lists of A and B will be incompatible unless users agree on a common name.
Huh?
typedef struct { int x; } A;
typedef struct { int x; } B;
typedef struct { header_list header; A payload; } list_of_A;
typedef struct { header_list header; B payload; } list_of_B;