Fix for Windows

Author: scotts

src/torchcodec/_core/AVIOFileLikeContext.h

@@ -11,14 +11,27 @@
 
 #include "src/torchcodec/_core/AVIOContextHolder.h"
 
+// pybind11 has specific visibility rules; see:
+//  https://pybind11.readthedocs.io/en/stable/faq.html#someclass-declared-with-greater-visibility-than-the-type-of-its-field-someclass-member-wattributes
+// This file is included in both pybind_ops.cpp and custom_ops.cpp. We compile
+// pybind_ops.cpp with the global visibility flag as required. On the
+// custom_ops.cpp side we don't need to do that. However, we do need to ensure
+// that this class is also seen as the same visibility.
+//
+// This only matters on Linux and Mac; on Windows we don't need to do anything.
+#ifdef _WIN32
+#define VISIBILITY_HIDDEN
+#else
+#define VISIBILITY_HIDDEN __attribute__((visibility("hidden")))
+#endif
+
 namespace py = pybind11;
 
 namespace facebook::torchcodec {
 
 // Enables uers to pass in a Python file-like object. We then forward all read
 // and seek calls back up to the methods on the Python object.
-class __attribute__((visibility("hidden"))) AVIOFileLikeContext
-    : public AVIOContextHolder {
+class VISIBILITY_HIDDEN AVIOFileLikeContext : public AVIOContextHolder {
  public:
   explicit AVIOFileLikeContext(const py::object& fileLike, bool isForWriting);
 

src/torchcodec/_core/custom_ops.cpp

@@ -207,10 +207,12 @@ at::Tensor create_from_tensor(
     realSeek = seekModeFromString(seek_mode.value());
   }
 
-  auto contextHolder = std::make_unique<AVIOFromTensorContext>(video_tensor);
+  auto avioContextHolder =
+      std::make_unique<AVIOFromTensorContext>(video_tensor);
 
   std::unique_ptr<SingleStreamDecoder> uniqueDecoder =
-      std::make_unique<SingleStreamDecoder>(std::move(contextHolder), realSeek);
+      std::make_unique<SingleStreamDecoder>(
+          std::move(avioContextHolder), realSeek);
   return wrapDecoderPointerToTensor(std::move(uniqueDecoder));
 }
 
@@ -219,16 +221,18 @@ at::Tensor _create_from_file_like(
     std::optional<std::string_view> seek_mode) {
   auto fileLikeContext =
       reinterpret_cast<AVIOFileLikeContext*>(file_like_context);
-  TORCH_CHECK(fileLikeContext != nullptr, "file_like must be a valid pointer");
-  std::unique_ptr<AVIOFileLikeContext> contextHolder(fileLikeContext);
+  TORCH_CHECK(
+      fileLikeContext != nullptr, "file_like_context must be a valid pointer");
+  std::unique_ptr<AVIOFileLikeContext> avioContextHolder(fileLikeContext);
 
   SingleStreamDecoder::SeekMode realSeek = SingleStreamDecoder::SeekMode::exact;
   if (seek_mode.has_value()) {
     realSeek = seekModeFromString(seek_mode.value());
   }
 
   std::unique_ptr<SingleStreamDecoder> uniqueDecoder =
-      std::make_unique<SingleStreamDecoder>(std::move(contextHolder), realSeek);
+      std::make_unique<SingleStreamDecoder>(
+          std::move(avioContextHolder), realSeek);
   return wrapDecoderPointerToTensor(std::move(uniqueDecoder));
 }