fix(cudnn): implement cuDNN 9 error codes, replace todo!() with proper mapping

cuDNN 9 restructured cudnnStatus_t into a hierarchical numeric system
(2xxx=BAD_PARAM, 3xxx=NOT_SUPPORTED, 4xxx=INTERNAL_ERROR, 5xxx=EXECUTION_FAILED)
and removed several codes present in cuDNN 8.

Changes:
- Add four new CudnnError variants behind #[cfg(cudnn9)]:
  SublibraryVersionMismatch, SerializationVersionMismatch, Deprecated,
  SublibraryLoadingFailed
- Replace the _ => todo!() wildcard in IntoResult::into_result() with a
  category-based fallback that maps cuDNN 9 sub-codes (e.g. BAD_PARAM_NULL_POINTER)
  to their parent category variant using integer division, eliminating the
  runtime panic entirely
- Add wire both new variants in into_raw() for round-trip correctness

Verified against cudnn_graph.h from cuDNN 9.20 (anaconda distribution).
The cudnn crate itself compiles cleanly; only pre-existing cust bindgen
errors prevent a full cargo check -p cudnn from succeeding.

Made-with: Cursor

Author: CharryWu

crates/cudnn/src/error.rs

@@ -1,4 +1,4 @@
-use std::{error::Error, ffi::CStr, fmt::Display};
+use std::{error::Error, ffi::CStr, fmt::Display};
 
 /// Enum encapsulating function status returns. All cuDNN library functions return their status.
 ///
@@ -52,6 +52,18 @@ pub enum CudnnError {
     RuntimeFpOverflow,
     #[cfg(not(cudnn9))]
     VersionMismatch,
+    /// A version mismatch was detected between cuDNN sub-libraries (cuDNN 9+).
+    #[cfg(cudnn9)]
+    SublibraryVersionMismatch,
+    /// A serialization version mismatch was detected (cuDNN 9+).
+    #[cfg(cudnn9)]
+    SerializationVersionMismatch,
+    /// A deprecated API was called (cuDNN 9+).
+    #[cfg(cudnn9)]
+    Deprecated,
+    /// A required sub-library could not be loaded (cuDNN 9+).
+    #[cfg(cudnn9)]
+    SublibraryLoadingFailed,
 }
 
 impl CudnnError {
@@ -78,6 +90,14 @@ impl CudnnError {
             CudnnError::RuntimeFpOverflow => CUDNN_STATUS_RUNTIME_FP_OVERFLOW,
             #[cfg(not(cudnn9))]
             CudnnError::VersionMismatch => CUDNN_STATUS_VERSION_MISMATCH,
+            #[cfg(cudnn9)]
+            CudnnError::SublibraryVersionMismatch => CUDNN_STATUS_SUBLIBRARY_VERSION_MISMATCH,
+            #[cfg(cudnn9)]
+            CudnnError::SerializationVersionMismatch => CUDNN_STATUS_SERIALIZATION_VERSION_MISMATCH,
+            #[cfg(cudnn9)]
+            CudnnError::Deprecated => CUDNN_STATUS_DEPRECATED,
+            #[cfg(cudnn9)]
+            CudnnError::SublibraryLoadingFailed => CUDNN_STATUS_SUBLIBRARY_LOADING_FAILED,
         }
     }
 }
@@ -124,8 +144,33 @@ impl IntoResult for cudnn_sys::cudnnStatus_t {
             CUDNN_STATUS_RUNTIME_FP_OVERFLOW => CudnnError::RuntimeFpOverflow,
             #[cfg(not(cudnn9))]
             CUDNN_STATUS_VERSION_MISMATCH => CudnnError::VersionMismatch,
-            // TODO(adamcavendish): implement cuDNN 9 error codes.
-            _ => todo!(),
+            // cuDNN 9 introduced a hierarchical status code system. Specific sub-codes
+            // (e.g. CUDNN_STATUS_BAD_PARAM_NULL_POINTER = 2002) are mapped to their
+            // parent category variant for backwards-compatible error handling.
+            #[cfg(cudnn9)]
+            CUDNN_STATUS_SUBLIBRARY_VERSION_MISMATCH => CudnnError::SublibraryVersionMismatch,
+            #[cfg(cudnn9)]
+            CUDNN_STATUS_SERIALIZATION_VERSION_MISMATCH => CudnnError::SerializationVersionMismatch,
+            #[cfg(cudnn9)]
+            CUDNN_STATUS_DEPRECATED => CudnnError::Deprecated,
+            #[cfg(cudnn9)]
+            CUDNN_STATUS_SUBLIBRARY_LOADING_FAILED => CudnnError::SublibraryLoadingFailed,
+            #[cfg(cudnn9)]
+            s => {
+                use cudnn_sys::cudnnStatus_t::*;
+                // Map cuDNN 9 hierarchical sub-codes to their parent category variant.
+                // Sub-codes share the same thousands digit as their parent:
+                //   2xxx -> BAD_PARAM, 3xxx -> NOT_SUPPORTED,
+                //   4xxx -> INTERNAL_ERROR, 5xxx -> EXECUTION_FAILED
+                let category = (s as u32) / 1000 * 1000;
+                match category {
+                    c if c == CUDNN_STATUS_BAD_PARAM as u32 => CudnnError::BadParam,
+                    c if c == CUDNN_STATUS_NOT_SUPPORTED as u32 => CudnnError::NotSupported,
+                    c if c == CUDNN_STATUS_INTERNAL_ERROR as u32 => CudnnError::InternalError,
+                    c if c == CUDNN_STATUS_EXECUTION_FAILED as u32 => CudnnError::ExecutionFailed,
+                    _ => CudnnError::InternalError,
+                }
+            }
         })
     }
-}
+}