--- a/Cargo.toml	Sat May 03 18:42:11 2025 -0400
+++ b/Cargo.toml	Sun May 04 00:58:04 2025 -0400
@@ -11,3 +11,4 @@
 
 [dependencies]
 libc = "0.2.97"
+thiserror = "2.0.12"

--- a/src/constants.rs	Sat May 03 18:42:11 2025 -0400
+++ b/src/constants.rs	Sun May 04 00:58:04 2025 -0400
@@ -25,42 +25,75 @@
 pub const PAM_RADIO_TYPE: PamMessageStyle = 5;
 pub const PAM_BINARY_PROMPT: PamMessageStyle = 7;
 
-// The Linux-PAM return values
-// see /usr/include/security/_pam_types.h
+/// The Linux-PAM return values.
+/// For more detailed information, see
+/// /usr/include/security/_pam_types.h
 #[allow(non_camel_case_types, dead_code)]
-#[derive(Debug, PartialEq)]
+#[derive(Debug, PartialEq, thiserror::Error)]
 #[repr(C)]
 pub enum PamResultCode {
+    #[error("Not an error")]
     PAM_SUCCESS = 0,
+    #[error("dlopen() failure when dynamically loading a service module")]
     PAM_OPEN_ERR = 1,
+    #[error("symbol not found")]
     PAM_SYMBOL_ERR = 2,
+    #[error("error in service module")]
     PAM_SERVICE_ERR = 3,
+    #[error("system error")]
     PAM_SYSTEM_ERR = 4,
+    #[error("memory buffer error")]
     PAM_BUF_ERR = 5,
+    #[error("permission denied")]
     PAM_PERM_DENIED = 6,
+    #[error("authentication failure")]
     PAM_AUTH_ERR = 7,
+    #[error("cannot access authentication data due to insufficient credentials")]
     PAM_CRED_INSUFFICIENT = 8,
+    #[error("underlying authentication service cannot retrieve authentication information")]
     PAM_AUTHINFO_UNAVAIL = 9,
+    #[error("user not known to the underlying authentication module")]
     PAM_USER_UNKNOWN = 10,
+    #[error("retry limit reached; do not attempt further")]
     PAM_MAXTRIES = 11,
+    #[error("new authentication token required")]
     PAM_NEW_AUTHTOK_REQD = 12,
+    #[error("user account has expired")]
     PAM_ACCT_EXPIRED = 13,
+    #[error("cannot make/remove an entry for the specified session")]
     PAM_SESSION_ERR = 14,
+    #[error("underlying authentication service cannot retrieve user credentials")]
     PAM_CRED_UNAVAIL = 15,
+    #[error("user credentials expired")]
     PAM_CRED_EXPIRED = 16,
+    #[error("failure setting user credentials")]
     PAM_CRED_ERR = 17,
+    #[error("no module-specific data is present")]
     PAM_NO_MODULE_DATA = 18,
+    #[error("conversation error")]
     PAM_CONV_ERR = 19,
+    #[error("authentication token manipulation error")]
     PAM_AUTHTOK_ERR = 20,
+    #[error("authentication information cannot be recovered")]
     PAM_AUTHTOK_RECOVERY_ERR = 21,
+    #[error("authentication token lock busy")]
     PAM_AUTHTOK_LOCK_BUSY = 22,
+    #[error("authentication token aging disabled")]
     PAM_AUTHTOK_DISABLE_AGING = 23,
+    #[error("preliminary check by password service")]
     PAM_TRY_AGAIN = 24,
+    #[error("ignore underlying account module, regardless of control flag")]
     PAM_IGNORE = 25,
+    #[error("critical error; this module should fail now")]
     PAM_ABORT = 26,
+    #[error("authentication token has expired")]
     PAM_AUTHTOK_EXPIRED = 27,
+    #[error("module is not known")]
     PAM_MODULE_UNKNOWN = 28,
+    #[error("bad item passed to pam_[whatever]_item")]
     PAM_BAD_ITEM = 29,
+    #[error("conversation function is event-driven and data is not available yet")]
     PAM_CONV_AGAIN = 30,
+    #[error("call this function again to complete authentication stack")]
     PAM_INCOMPLETE = 31,
 }