[RFC,v1] py: Use smart holder for `Camera` if available
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Message ID 20260519072152.346204-1-barnabas.pocze@ideasonboard.com
State New
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Series
  • [RFC,v1] py: Use smart holder for `Camera` if available
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Commit Message

Barnabás Pőcze May 19, 2026, 7:21 a.m. UTC 
The `Camera` class has a private destructor, so `std::shared_ptr<>` cannot
be used as a holder type. In recent versions of pybind11, the custom holder
type that was used no longer works:

  RuntimeError: Unable to convert std::shared_ptr<T> to Python when the bound
  type does not use std::shared_ptr or py::smart_holder as its holder type

This appears to be intentional and the fact that it worked is accidental.

Fix that by using a "smart holder" since pybind11 3.x, and falling back to
the custom one in previous versions.

Link: https://github.com/pybind/pybind11/issues/6064
Closes: https://gitlab.freedesktop.org/camera/libcamera/-/work_items/334
---
 src/py/libcamera/py_main.cpp | 12 ++++++++++--
 1 file changed, 10 insertions(+), 2 deletions(-)

Patch
diff mbox series 

diff --git a/src/py/libcamera/py_main.cpp b/src/py/libcamera/py_main.cpp
index d0ef6915b..3b101f996 100644
--- a/src/py/libcamera/py_main.cpp
+++ b/src/py/libcamera/py_main.cpp
@@ -34,6 +34,7 @@  LOG_DEFINE_CATEGORY(Python)
 
 }
 
+#if PYBIND11_VERSION_MAJOR < 3
 /*
  * This is a holder class used only for the Camera class, for the sole purpose
  * of avoiding the compilation issue with Camera's private destructor.
@@ -79,6 +80,13 @@  private:
 
 PYBIND11_DECLARE_HOLDER_TYPE(T, PyCameraSmartPtr<T>)
 
+using PyCameraHolder = PyCameraSmartPtr<Camera>;
+using PyCameraArg = PyCameraSmartPtr<Camera>;
+#else
+using PyCameraHolder = py::smart_holder;
+using PyCameraArg = std::shared_ptr<Camera>;
+#endif
+
 /*
  * Note: global C++ destructors can be ran on this before the py module is
  * destructed.
@@ -103,7 +111,7 @@  PYBIND11_MODULE(_libcamera, m)
 	 */
 
 	auto pyCameraManager = py::class_<PyCameraManager, std::shared_ptr<PyCameraManager>>(m, "CameraManager");
-	auto pyCamera = py::class_<Camera, PyCameraSmartPtr<Camera>>(m, "Camera");
+	auto pyCamera = py::class_<Camera, PyCameraHolder>(m, "Camera");
 	auto pySensorConfiguration = py::class_<SensorConfiguration>(m, "SensorConfiguration");
 	auto pyCameraConfiguration = py::class_<CameraConfiguration>(m, "CameraConfiguration");
 	auto pyCameraConfigurationStatus = py::enum_<CameraConfiguration::Status>(pyCameraConfiguration, "Status");
@@ -347,7 +355,7 @@  PYBIND11_MODULE(_libcamera, m)
 		.def("range", &StreamFormats::range);
 
 	pyFrameBufferAllocator
-		.def(py::init<PyCameraSmartPtr<Camera>>(), py::keep_alive<1, 2>())
+		.def(py::init<PyCameraArg>(), py::keep_alive<1, 2>())
 		.def("allocate", [](FrameBufferAllocator &self, Stream *stream) {
 			int ret = self.allocate(stream);
 			if (ret < 0)