--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/libpam-sys/src/aliases.rs	Mon Jul 07 12:11:43 2025 -0400
@@ -0,0 +1,48 @@
+//! Convenience aliases for complex types in PAM.
+
+use super::{pam_conv, pam_handle, pam_message, pam_response, pam_set_data};
+use std::ffi::{c_int, c_void};
+
+/// The type of [`pam_conv::conv`].
+///
+/// The exact format of `messages` varies between Linux-PAM and other
+/// implementations. See `libpam_sys_helpers::PtrPtrVec` for details
+/// (and a workaround).
+///
+/// ```no_run
+/// use libpam_sys::pam_conv;
+/// use libpam_sys::aliases::ConversationCallback;
+/// fn convo() -> ConversationCallback {
+///     // ...
+/// #    unimplemented!()
+/// }
+/// let conv = pam_conv{conv: convo(), appdata_ptr: std::ptr::null_mut()};
+/// ```
+pub type ConversationCallback = unsafe extern "C" fn(
+    num_msg: c_int,
+    msg: *const *const pam_message,
+    resp: *mut *mut pam_response,
+    appdata: *mut c_void,
+) -> c_int;
+
+/// Alias for the callback to [`pam_set_data`].
+///
+/// ```no_run
+/// # use std::ffi::CString;
+/// use libpam_sys::pam_set_data;
+/// use libpam_sys::aliases::CleanupCallback;
+/// # use libpam_sys::pam_handle;
+/// # let handle: *mut pam_handle = std::ptr::null_mut();
+/// # let mut my_data = 100;
+/// # let data_ptr = &mut my_data as *mut i32;
+/// fn cleanup() -> CleanupCallback {
+///     // ...
+/// #    unimplemented!()
+/// }
+/// let name = CString::new("name").unwrap();
+/// unsafe {
+///     pam_set_data(handle, name.as_ptr().cast_mut(), data_ptr.cast(), cleanup());
+/// }
+/// ```
+pub type CleanupCallback =
+    unsafe extern "C" fn(pamh: *mut pam_handle, data: *mut c_void, pam_end_status: c_int);