fix(cuda.bindings): make cythonization warning-clean and enable -Werror

cuda_bindings/build_hooks.py

@@ -131,6 +131,7 @@ def _build_cuda_bindings(debug=False):
     that metadata queries do not require a CUDA toolkit installation.
     """
     from Cython.Build import cythonize
+    from Cython.Compiler import Options as _CythonOptions
 
     global _extensions
 
@@ -224,6 +225,7 @@ def get_static_libraries(f):
         )
 
     # Cythonize
+    _CythonOptions.warning_errors = True
     cython_directives = {"language_level": 3, "embedsignature": True, "binding": True, "freethreading_compatible": True}
     if compile_for_coverage:
         cython_directives["linetrace"] = True

cuda_bindings/cuda/bindings/_lib/windll.pxd

@@ -14,7 +14,7 @@ cdef extern from "windows.h" nogil:
     ctypedef const char *LPCSTR
     ctypedef int BOOL
 
-    cdef DWORD LOAD_LIBRARY_SEARCH_SYSTEM32 = 0x00000800
+    const DWORD LOAD_LIBRARY_SEARCH_SYSTEM32
 
     HMODULE _LoadLibraryExW "LoadLibraryExW"(
         LPCWSTR lpLibFileName,

cuda_bindings/cuda/bindings/cudla.pxd

@@ -3,7 +3,7 @@
 
 # This code was automatically generated across versions from 1.5.0 to 13.3.0. Do not modify it directly.
 
-# CYTHON-BINDINGS-GENERATED-DO-NOT-MODIFY-THIS-FILE: format=1; content-sha256=e64a78a1b3e010d167373d7c9635ff4637dfd1a6a38ffafb671dcde4e12aaaad
+# CYTHON-BINDINGS-GENERATED-DO-NOT-MODIFY-THIS-FILE: format=1; content-sha256=b3303a34762cec1db0d9ab7662fe4a4a0f5b80350810cc0b646a04c9c6bb19c3
 from libc.stdint cimport intptr_t
 
 from .cycudla cimport *
@@ -44,10 +44,10 @@ cpdef intptr_t mem_register(intptr_t dev_handle, intptr_t ptr, size_t size, uint
 cpdef intptr_t module_load_from_memory(intptr_t dev_handle, p_module, size_t module_size, uint32_t flags) except *
 cpdef module_unload(intptr_t h_module, uint32_t flags)
 cpdef submit_task(intptr_t dev_handle, intptr_t ptr_to_tasks, uint32_t num_tasks, intptr_t stream, uint32_t flags)
-cpdef object device_get_attribute(intptr_t dev_handle, int attrib) except *
+cpdef object device_get_attribute(intptr_t dev_handle, int attrib)
 cpdef mem_unregister(intptr_t dev_handle, intptr_t dev_ptr)
 cpdef int get_last_error(intptr_t dev_handle) except? 0
 cpdef destroy_device(intptr_t dev_handle)
 cpdef set_task_timeout_in_ms(intptr_t dev_handle, uint32_t timeout)
 
-cpdef module_get_attributes(intptr_t h_module, int attr_type) except *
+cpdef module_get_attributes(intptr_t h_module, int attr_type)

cuda_bindings/cuda/bindings/cudla.pyx

@@ -2,7 +2,7 @@
 # SPDX-License-Identifier: Apache-2.0
 
 # This code was automatically generated across versions from 1.5.0 to 13.3.0. Do not modify it directly.
-# CYTHON-BINDINGS-GENERATED-DO-NOT-MODIFY-THIS-FILE: format=1; content-sha256=b793aebd0586162e23d26c82e2bd54c21675584e3c23d6e443f3a83c61a8674c
+# CYTHON-BINDINGS-GENERATED-DO-NOT-MODIFY-THIS-FILE: format=1; content-sha256=ee04e18498a1e4e597afcdead5590bfe22af25afb2d43cd85b19089bee10a721
 
 
 # <<<< PREAMBLE CONTENT >>>>
@@ -1776,7 +1776,7 @@ cpdef submit_task(intptr_t dev_handle, intptr_t ptr_to_tasks, uint32_t num_tasks
     check_status(__status__)
 
 
-cpdef object device_get_attribute(intptr_t dev_handle, int attrib) except *:
+cpdef object device_get_attribute(intptr_t dev_handle, int attrib):
     cdef DevAttribute p_attribute_py = DevAttribute()
     cdef cudlaDevAttribute *p_attribute = <cudlaDevAttribute *><intptr_t>(p_attribute_py._get_ptr())
     with nogil:
@@ -1810,7 +1810,7 @@ cpdef set_task_timeout_in_ms(intptr_t dev_handle, uint32_t timeout):
     check_status(__status__)
 
 
-cpdef module_get_attributes(intptr_t h_module, int attr_type) except *:
+cpdef module_get_attributes(intptr_t h_module, int attr_type):
     """Query module attributes, interpreting the cudlaModuleAttribute union
     based on the requested attribute type.
 

cuda_bindings/tests/test_cython_warning_cleanliness.py

@@ -0,0 +1,76 @@
+# SPDX-FileCopyrightText: Copyright (c) 2026 NVIDIA CORPORATION & AFFILIATES. All rights reserved.
+# SPDX-License-Identifier: Apache-2.0
+
+"""Regression guards for cuda.bindings Cython warning cleanliness (#2450)."""
+
+from __future__ import annotations
+
+import ast
+import re
+from pathlib import Path
+
+import pytest
+
+_BINDINGS_ROOT = Path(__file__).resolve().parents[1]
+_CUDA_BINDINGS = _BINDINGS_ROOT / "cuda" / "bindings"
+
+# cpdef returning a Python object must not carry an exception clause; Cython
+# warns (and with warning_errors, fails) that the clause is ignored.
+_CPDEF_OBJECT_EXCEPT_RE = re.compile(
+    r"^\s*cpdef\s+object\s+\w+\s*\([^)]*\)\s+except\b",
+    re.MULTILINE,
+)
+_MODULE_GET_ATTRIBUTES_EXCEPT_RE = re.compile(
+    r"^\s*cpdef\s+module_get_attributes\s*\([^)]*\)\s+except\b",
+    re.MULTILINE,
+)
+
+
+@pytest.mark.agent_authored(model="grok-4.5")
+def test_build_hooks_enable_cython_warning_errors():
+    """Source builds must treat Cython warnings as errors."""
+    source = (_BINDINGS_ROOT / "build_hooks.py").read_text(encoding="utf-8")
+    tree = ast.parse(source)
+    assigned = {
+        node.targets[0].attr
+        for node in ast.walk(tree)
+        if isinstance(node, ast.Assign)
+        and len(node.targets) == 1
+        and isinstance(node.targets[0], ast.Attribute)
+        and isinstance(node.value, ast.Constant)
+        and node.value.value is True
+    }
+    assert "warning_errors" in assigned, "cuda_bindings/build_hooks.py must set Cython Options.warning_errors = True"
+
+
+@pytest.mark.agent_authored(model="grok-4.5")
+def test_windll_pxd_declares_load_library_flag_as_const():
+    """Assignment in a ``.pxd`` is not executed; declare the Win32 flag as const."""
+    text = (_CUDA_BINDINGS / "_lib" / "windll.pxd").read_text(encoding="utf-8")
+    assert "LOAD_LIBRARY_SEARCH_SYSTEM32" in text
+    assert re.search(
+        r"^\s*const\s+DWORD\s+LOAD_LIBRARY_SEARCH_SYSTEM32\s*$",
+        text,
+        re.MULTILINE,
+    ), "LOAD_LIBRARY_SEARCH_SYSTEM32 must be declared as const DWORD (no assignment)"
+    assert (
+        re.search(
+            r"LOAD_LIBRARY_SEARCH_SYSTEM32\s*=",
+            text,
+        )
+        is None
+    )
+
+
+@pytest.mark.agent_authored(model="grok-4.5")
+@pytest.mark.parametrize("filename", ["cudla.pxd", "cudla.pyx"])
+def test_cudla_cpdef_python_returns_have_no_except_clause(filename):
+    """Regression for cybind emitting ``except *`` on Python-returning cpdefs."""
+    text = (_CUDA_BINDINGS / filename).read_text(encoding="utf-8")
+    assert _CPDEF_OBJECT_EXCEPT_RE.search(text) is None, (
+        f"{filename} has cpdef object ... except ..., which Cython warns about"
+    )
+    # Declared without an explicit object return type, but returns Python values.
+    assert _MODULE_GET_ATTRIBUTES_EXCEPT_RE.search(text) is None, (
+        f"{filename}: cpdef module_get_attributes(...) except ... is invalid for Python returns"
+    )