The definitions of those identifiers, written as Go functions, types,
or variables, are provided in _cgo_gotypes.go.

Here is a _cgo_gotypes.go containing definitions for needed C types:

	type _Ctype_char int8
	type _Ctype_int int32
	type _Ctype_void [0]byte

The _cgo_gotypes.go file also contains the definitions of the
functions. They all have similar bodies that invoke runtime·cgocall

		}
		if def := typedef[t.Name]; def != nil {
			return p.hasPointer(f, def.Go, top)
		}
		if t.Name == "string" {
			return !top
		}
		if t.Name == "error" {
			return true
		}
		if goTypes[t.Name] != nil {
			return false
		}
		// We can't figure out the type. Conservative
		// approach is to assume it has a pointer.
		return true
	case *ast.SelectorExpr: