python: multi_usrp: Let get_tree() return a raw pointer

This changes the Python version of MultiUSRP.get_tree() such that it
returns a raw pointer to the tree instead of returning the sptr.
This fixes an issue where calling get_tree() will reliably cause
a segfault during garbage collection, at least on some USRPs.

The downside of this approach is that storing the return value from
get_tree() can produce a dangling pointer when the underlying object is
destroyed. It's still better than segfaults, and the recommended way to
use get_tree() anyway is not to store the return value (unless it's in
a local scope), but tack on property tree methods to get_tree() itself.
Examples:
>>> usrp = uhd.usrp.MultiUSRP('...')
>>> usrp.get_tree().exists('/path/to/prop') # This is fine

This change has no noticable API changes.

1 files changed, 1 insertions, 1 deletions

diff --git a/host/lib/usrp/multi_usrp_python.cpp b/host/lib/usrp/multi_usrp_python.cpp
index 34bb96338..b26671760 100644
--- a/host/lib/usrp/multi_usrp_python.cpp
+++ b/host/lib/usrp/multi_usrp_python.cpp
@@ -29,7 +29,7 @@ void export_multi_usrp(py::module& m)
         .def(py::init(&multi_usrp::make))
 
         // clang-format off
-        .def("get_tree"                , &multi_usrp::get_tree)
+        .def("get_tree"                , [](multi_usrp& self){ return self.get_tree().get(); }, py::return_value_policy::reference_internal)
 
         // General USRP methods
         .def("get_rx_freq"             , &multi_usrp::get_rx_freq, py::arg("chan") = 0)