Remove visibility stuff from source code, add it to cmake

Author: scotts

src/torchcodec/_core/AVIOFileLikeContext.h

@@ -11,27 +11,13 @@
 
 #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 VISIBILITY_HIDDEN AVIOFileLikeContext : public AVIOContextHolder {
+class AVIOFileLikeContext : public AVIOContextHolder {
  public:
   explicit AVIOFileLikeContext(const py::object& fileLike, bool isForWriting);
 

src/torchcodec/_core/CMakeLists.txt

@@ -175,12 +175,19 @@ function(make_torchcodec_libraries
     # stray initialization of py::objects. The rest of the object code must
     # match. See:
     #   https://pybind11.readthedocs.io/en/stable/faq.html#someclass-declared-with-greater-visibility-than-the-type-of-its-field-someclass-member-wattributes
+    # We have to do this for both pybind_ops and custom_ops because they include
+    # some of the same headers.
     if(NOT WIN32)
         target_compile_options(
             ${pybind_ops_library_name}
             PUBLIC
             "-fvisibility=hidden"
         )
+        target_compile_options(
+            ${custom_ops_library_name}
+            PUBLIC
+            "-fvisibility=hidden"
+        )
     endif()
 
     # The value we use here must match the value we return from