OOT python module import error

[tkuraku]

I have tried this on master, 4.9.0.1, 4.9.0.0.

I built UHD from source, then built the rfnoc-gain example python interface. Everything built without error.

When I go to import the rfnoc_gain module in python I get the following error message.

ImportError: generic_type: type "gain_block_control" referenced unknown base type "uhd::rfnoc::noc_block_base"

Any idea how to resolve this issue?

[mbr0wn]

Is this on Windows? If yes, we are aware of this issue and are working on a fix.

[tkuraku]

This is on Linux. Rhel and Ubuntu? Do you have a patch I can use?

[mbr0wn]

Try this:

diff --git a/host/examples/rfnoc-gain/lib/CMakeLists.txt b/host/examples/rfnoc-gain/lib/CMakeLists.txt
index ebd7baac5f..b7f9935f13 100644
--- a/host/examples/rfnoc-gain/lib/CMakeLists.txt
+++ b/host/examples/rfnoc-gain/lib/CMakeLists.txt
@@ -37,11 +37,10 @@ add_library(rfnoc-gain SHARED
  ${rfnoc_gain_sources}
)
target_link_libraries(rfnoc-gain
-    ${UHD_LIBRARIES}
-    ${Boost_LIBRARIES}
+    UHD::uhd
)
set_target_properties(rfnoc-gain
-    PROPERTIES DEFINE_SYMBOL "RFNOC_GAIN_EXPORTS")
+    PROPERTIES DEFINE_SYMBOL "RFNOC_GAIN_DLL_EXPORTS")

file(GENERATE OUTPUT ${CMAKE_BINARY_DIR}/lib/rfnoc-gain CONTENT "$<TARGET_FILE_NAME:rfnoc-gain>\n")

diff --git a/host/examples/rfnoc-gain/python/CMakeLists.txt b/host/examples/rfnoc-gain/python/CMakeLists.txt
index 28712d9340..a7bfa4bb1b 100644
--- a/host/examples/rfnoc-gain/python/CMakeLists.txt
+++ b/host/examples/rfnoc-gain/python/CMakeLists.txt
@@ -32,11 +32,20 @@ target_include_directories(${PYMODULE_NAME}_python
${Python3_INCLUDE_DIRS}
${Python3_NumPy_INCLUDE_DIRS}
)
+# If PYBIND11_INCLUDE_DIR is set (e.g., to UHD's bundled pybind11 headers),
+# prepend it so the OOT Python module uses the same pybind11 version as UHD.
+# This ensures pybind11's type registry is shared between DLLs on Windows.
+if(PYBIND11_INCLUDE_DIR)
+  target_include_directories(${PYMODULE_NAME}_python BEFORE
+    PRIVATE ${PYBIND11_INCLUDE_DIR}
+  )
+endif()
target_link_libraries(
${PYMODULE_NAME}_python
PRIVATE
pybind11::pybind11
-  ${UHD_LIBRARIES}
+  UHD::uhd
+  rfnoc-gain
)

# Copy pybind bindings library to the staging directory (it will get copied to
diff --git a/host/examples/rfnoc-gain/python/pyrfnoc-gain.cpp b/host/examples/rfnoc-gain/python/pyrfnoc-gain.cpp
index b0fb2288bc..701aa13320 100644
--- a/host/examples/rfnoc-gain/python/pyrfnoc-gain.cpp
+++ b/host/examples/rfnoc-gain/python/pyrfnoc-gain.cpp
@@ -33,6 +33,10 @@ PYBIND11_MODULE(rfnoc_gain_python, m)
  // (otherwise we will see segmentation faults)
  init_numpy();

+    // Import UHD's rfnoc Python module so pybind11 can resolve
+    // noc_block_base across the DLL boundary on Windows.
+    py::module_::import("uhd.libpyuhd.rfnoc");
+
  // uhd::rfnoc::python::export_noc_block_base(m);
  export_gain_block_control(m);
}                                                                                                             

[mbr0wn]

The last hunk is probably the only one that you need.

[tkuraku]

I still have the same problem. This is on RHEL 9.7

[mbr0wn]

@tkuraku hm, I don't have access to an RHEL 9.7, but on Ubuntu, I could see the exact same problem as you saw. However, when I apply the patch, it goes away.

Can you double-check the following:

• Are you compiling rfnoc-gain in-tree, i.e., you are sure that you are getting the patches mentioned above? Like I said, the relevant hunk is the last one (the comment about Windows is misleading).
  • The same goes for your OOT module, it needs the same patch.
• Can you check that after installation, the DLL lookup is properly resolved? On my dev setup, it looks like this (abbreviated)

$ ldd $PREFIX/lib/python3.12/site-packages/rfnoc_gain/rfnoc_gain_python.cpython-312-x86_64-linux-gnu.so
        linux-vdso.so.1 (0x00007fff32184000)
        libuhd.so.4.10.0 => $PREFIX/lib/libuhd.so.4.10.0 (0x00007f0a35ceb000)
        [...]

[mbr0wn]

You can simply include the py::module_::import("uhd.libpyuhd.rfnoc"); line in your python/pyrfnoc-XXX.cpp file if you want the fastest way to resolve this.

[mbr0wn]

Can you run ldd on your libpyuhd.cpython-312-x86_64-linux-gnu.so file? Just to check it's picking up the right libuhd.so.

Sorry, I already asked this above.

[tkuraku]

I added that line to the python cpp file and ran the ldd command. Everything resolved as expected. But I still get the same error when informing rfnoc_gain in python. This is on RHEL and 4.9.0.1.

[mbr0wn]

I went back to UHD 4.9.0.1 and was able to see the same issues. Without this patch, I see the same error message as you do. With the patch, it's gone.

This was still on Ubuntu, though. Is there anything that you can think of that's RHEL specific that could cause this?

[mbr0wn]

Wait -- how did you install pybind11?

[mbr0wn]

Where I'm going with this: Your UHD install might have picked up UHD's vendored version of Pybind11, but your OOT might be using a different one.

[mbr0wn]

...I was able to reproduce this with Rocky Linux 10.1.