fix(core.utils): hash extra_sources and use_libdevice in cache key

make_program_cache_key() only hashed options.as_bytes() which omits
NVVM-specific fields (extra_sources, use_libdevice). Two NVVM
compilations with different extra_sources could produce the same
cache key, returning wrong cached object code.

Also adds docstring warnings about pickle trust model (cache dirs
should be treated as trusted build artifacts) and path-backed
ObjectCode instability (normalize to bytes before caching).

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: cpcloud

cuda_core/cuda/core/utils/_program_cache.py

@@ -73,6 +73,20 @@ class ProgramCacheResource(abc.ABC):
     Concrete implementations store and retrieve :class:`~cuda.core.ObjectCode`
     instances keyed by arbitrary hashable objects. A typical key is produced
     by :func:`make_program_cache_key`, but any hashable value is acceptable.
+
+    .. warning::
+
+        Persistent backends use :mod:`pickle` for serialization. Only read
+        cache files that you trust — loading a cache from an untrusted source
+        can execute arbitrary code. Cache directories should have the same
+        access controls as any other sensitive build artifact.
+
+    .. note::
+
+        Cache only bytes-backed ``ObjectCode`` instances. Path-backed objects
+        (created via ``ObjectCode.from_cubin("/path")``) store the path, not
+        the content — if the file is later modified or deleted, cache hits
+        will return stale or broken data. Normalize to bytes before caching.
     """
 
     @abc.abstractmethod
@@ -256,6 +270,22 @@ def _update(label: str, payload: bytes) -> None:
     for n in names:
         _update("name", n.encode("utf-8"))
 
+    # Hash fields that affect compilation output but are not captured by
+    # options.as_bytes() (which only emits CLI-style flags). Without these,
+    # two NVVM compilations with different extra_sources or use_libdevice
+    # could collide on the same key.
+    extra_sources = getattr(options, "extra_sources", None)
+    if extra_sources:
+        _update("extra_sources_count", str(len(extra_sources)).encode("ascii"))
+        for src in extra_sources:
+            if isinstance(src, str):
+                _update("extra_source", src.encode("utf-8"))
+            elif isinstance(src, (bytes, bytearray)):
+                _update("extra_source", bytes(src))
+    use_libdevice = getattr(options, "use_libdevice", None)
+    if use_libdevice is not None:
+        _update("use_libdevice", str(use_libdevice).encode("ascii"))
+
     return hasher.digest()