Why does libcap use obfuscated pointer for cap_t

Question

Why is cap_t defined as _cap_struct *? What was the reasoning for obfuscating the pointer type and having libcap functions take/return cap_t when normal libc usage suggests they would take/return a explicit pointer type?

Answer 1

Obfuscated pointers (actually "opaque") are used to force applications to use the documented functions for a library rather than bypass those functions and manipulate its data directly.

Doing that lets the developers (of the library) concentrate on making the functions work rather than being distracted by handling data inconsistencies.

Further reading:

• What is an opaque value?
• Opaque C structs: how should they be declared?
• Why use an opaque “handle” that requires casting in a public API rather than a typesafe struct pointer?