Revert "Merge SPDL_HOLD_GIL and NB_FREE_THREADED macro (#223)" (#241)

This reverts commit fe21d11.

In Python 3.13 there are three kinds of mode

1. Built with GIL enabled
2. Built with GIL disabled, executed with GIL enabled
3. Built with GIL disabled, executed with GIL disabled

The runtime GIl is determined either by flag `-Xgil`, env var
`PYTHON_GIL`, or whether a module complied with GIL enabled is imported
or not.

So keeping a separate `SPDL_HOLD_GIL` option, allows to support all the
build modes.

CMakeLists.txt

@@ -9,6 +9,7 @@ option(SPDL_USE_NPPI "Enable NVIDIA 2D Image And Signal Performance Primitives s
 option(SPDL_LINK_STATIC_NVJPEG "Link nvJPEG and NPPI statically." OFF)
 
 option(SPDL_DEBUG_REFCOUNT "Enable debug print for reference counting of AVFrame objects." OFF)
+option(SPDL_HOLD_GIL "Hold GIL in IO functions." OFF)
 option(SPDL_BUILD_STUB "Build Python binding stub file" OFF)
 option(SPDL_BUILD_PYTHON_BINDING "Build Python binding" ON)
 

setup.py

@@ -111,6 +111,7 @@ def _b(var):
             f"-DSPDL_USE_FFMPEG_VERSION={_SPDL_USE_FFMPEG_VERSION}",
             f"-DSPDL_DEBUG_REFCOUNT={_b(_env('SPDL_DEBUG_REFCOUNT'))}",
             f"-DSPDL_BUILD_STUB={_b(_SPDL_BUILD_STUB)}",
+            f"-DSPDL_HOLD_GIL={_b(_env('SPDL_HOLD_GIL', False))}",
             ###################################################################
             f"-DPython_INCLUDE_DIR={sysconfig.get_paths()['include']}",
             "-GNinja",

src/binding/CMakeLists.txt

@@ -42,6 +42,9 @@ function(add_spdl_extension ffmpeg_version)
   if (SPDL_USE_NVCODEC)
     list(APPEND defs SPDL_USE_NVCODEC)
   endif ()
+  if (SPDL_HOLD_GIL)
+    list(APPEND defs SPDL_HOLD_GIL)
+  endif ()
 
   nanobind_add_module(${name} ${src})
   target_compile_definitions(${name} PRIVATE "${defs}")

src/binding/core/gil.h

@@ -10,8 +10,8 @@
 
 #include <nanobind/nanobind.h>
 
-#ifdef NB_FREE_THREADED
-#define RELEASE_GIL() // do not release GIL in FT Python
+#ifdef SPDL_HOLD_GIL
+#define RELEASE_GIL()
 #else
 #define RELEASE_GIL() nb::gil_scoped_release __g;
 #endif