[Windows] Fix CUDA build by disabling ClangCL toolset for CUDA builds

install_utils.py

@@ -108,10 +108,18 @@ def determine_torch_url(torch_nightly_url_base, supported_cuda_versions):
         URL string for PyTorch packages
     """
     if platform.system().lower() == "windows":
-        print(
-            "Windows detected, using CPU-only PyTorch until CUDA support is available"
-        )
-        return f"{torch_nightly_url_base}/cpu"
+        # Try CUDA detection on Windows as well
+        print("Windows detected, attempting CUDA detection...")
+        try:
+            cuda_version = _get_cuda_version(supported_cuda_versions)
+            major, minor = cuda_version
+            print(f"Detected CUDA version: {major}.{minor}")
+            torch_url = _get_pytorch_cuda_url(cuda_version, torch_nightly_url_base)
+            print(f"Using PyTorch URL: {torch_url}")
+            return torch_url
+        except Exception as err:
+            print(f"CUDA detection failed ({err}), using CPU-only PyTorch")
+            return f"{torch_nightly_url_base}/cpu"
 
     print("Attempting to detect CUDA via nvcc...")
 

setup.py

@@ -677,9 +677,14 @@ def run(self):  # noqa C901
             f"-DCMAKE_BUILD_TYPE={cmake_build_type}",
         ]
 
-        # Use ClangCL on Windows.
+        # Use ClangCL on Windows, but not when building with CUDA
+        # (CUDA 12.x MSBuild targets have compatibility issues with ClangCL)
         if _is_windows():
-            cmake_configuration_args += ["-T ClangCL"]
+            # Check if CUDA build is enabled via CMAKE_ARGS environment variable
+            cmake_args_env = os.environ.get("CMAKE_ARGS", "")
+            cuda_enabled = "EXECUTORCH_BUILD_CUDA=ON" in cmake_args_env
+            if not cuda_enabled:
+                cmake_configuration_args += ["-T ClangCL"]
 
         # Allow adding extra cmake args through the environment. Used by some
         # tests and demos to expand the set of targets included in the pip

torch_pin.py

@@ -1,2 +1,2 @@
 TORCH_VERSION = "2.10.0"
-NIGHTLY_VERSION = "dev20251120"
+NIGHTLY_VERSION = "dev20251016"