How to declare an opaque struct in Adept?

[ghost]

In C, it's typedef struct _user_data UserData. What is the equivalent syntax in Adept? Is struct UserData () valid?

[IsaacShelton]

For opaque structs, you can either have an empty definition which will work as long as you don't need to allocate it from Adept.

struct UserData ()

Or if you require the ability to allocate space for it without knowing what's inside, you can put dummy data inside of the struct. This is what the definition of the FILE type from libc looks like for example:

struct FILE (_opaque 32 usize)

which says that FILE should never take more than 32 * 8 = 256 bytes.

Most of the time, if you have an opaque struct, you only pass it around by pointer and don't access the fields directly or allocate it directly, so struct UserData () is usually sufficient.

TL;DR

For fully opaque structs, struct UserData () is correct