From daba5bf6c806e6b938cbf17b8dc4db34e3e996de Mon Sep 17 00:00:00 2001
From: jrstevens <jrstevens@fb.com>
Date: Fri, 17 Jul 2026 11:31:49 -0700
Subject: [PATCH] Fix portable pybindings COW ABI dependency

Summary:
Avoid at::Tensor::data_ptr() in portable pybindings input conversion by using storage-level no-COW pointer access with the tensor storage offset. This prevents _portable_lib from depending on removed or renamed COW ABI symbols in newer Torch builds.

Test Plan:
cmake --build pip-out/temp.linux-x86_64-cpython-311/cmake-out --target portable_lib --config=Release -j8
nm -D pip-out/temp.linux-x86_64-cpython-311/cmake-out/_portable_lib.cpython-311-x86_64-linux-gnu.so | c++filt | rg "c10::impl::cow|materialize_cow|is_cow_data_ptr" -n || true
Direct-loaded rebuilt _portable_lib in Python and verified ExecuTorchModule is present.
---
 extension/pybindings/pybindings.cpp | 30 +++++++++++++++++++++++------
 1 file changed, 24 insertions(+), 6 deletions(-)

diff --git a/extension/pybindings/pybindings.cpp b/extension/pybindings/pybindings.cpp
index 7e96af21a18..c71d91e5933 100644
--- a/extension/pybindings/pybindings.cpp
+++ b/extension/pybindings/pybindings.cpp
@@ -112,6 +112,22 @@ namespace pybindings {
 
 namespace {
 
+void* mutable_tensor_data_ptr_no_cow(at::Tensor& tensor) {
+  if (tensor.numel() == 0) {
+    return nullptr;
+  }
+
+  auto* storage_data = static_cast<char*>(tensor.unsafeGetTensorImpl()
+                                              ->unsafe_storage()
+                                              .unsafeGetStorageImpl()
+                                              ->_mutable_data_ptr_no_checks()
+                                              .mutable_get());
+  ET_CHECK_MSG(
+      storage_data != nullptr,
+      "Tensor has a non-zero number of elements, but its data is not allocated");
+  return storage_data + tensor.storage_offset() * tensor.itemsize();
+}
+
 void write_data_to_file(const std::string& path, void* buf, size_t size) {
   FILE* f = fopen(path.c_str(), "w+");
   if (!f) {
@@ -1117,12 +1133,14 @@ struct PyMethod final {
               " should be contiguous or channels-last.";
           throw std::runtime_error(error_msg);
         }
-        TensorPtr tensor =
-            for_blob(at_tensor.data_ptr(), std::move(sizes), type)
-                .strides(std::move(strides))
-                .dim_order(std::move(dim_order))
-                .dynamism(aten::TensorShapeDynamism::STATIC)
-                .make_tensor_ptr();
+        TensorPtr tensor = for_blob(
+                               mutable_tensor_data_ptr_no_cow(at_tensor),
+                               std::move(sizes),
+                               type)
+                               .strides(std::move(strides))
+                               .dim_order(std::move(dim_order))
+                               .dynamism(aten::TensorShapeDynamism::STATIC)
+                               .make_tensor_ptr();
         input_tensors.push_back(tensor);
         EValue evalue(input_tensors.back());
 #endif