Undefined symbol _ZN5torch7LibraryC1ENS0_4KindESsSt8optionalIN3c1011DispatchKeyEEPKcj

[bumi001]

I am posting this request for help here since the authors of extension-cpp-meson also contribute to this repo. I did the following to try to run it.

mkdir ~/cpp_tests
cd ~/cpp_tests
python3 -m venv .venv
source .venv/bin/activate
pip install torch numpy meson-python ninja
git clone https://github.com/daknuett/extension-cpp-meson.git
cd extension-cpp-meson
python -m pip install --no-build-isolation . -Cbuild-dir=build
cd
python
>>>import torch
>>>import extension_cpp

I get the following error:

Traceback (most recent call last):
File "", line 1, in
import extension_cpp
File "/home/sequoia/cpp_tests/.venv/lib/python3.13/site-packages/extension_cpp/init.py", line 3, in
from . import _C, ops
ImportError: /home/sequoia/cpp_tests/.venv/lib/python3.13/site-packages/extension_cpp/_C.cpython-313-x86_64-linux-gnu.so: undefined symbol: _ZN5torch7LibraryC1ENS0_4KindESsSt8optionalIN3c1011DispatchKeyEEPKcj

Any help in resolving this issue would be greatly appreciated!

[bumi001]

I built this code https://github.com/pytorch/extension-cpp which uses setuptools and tried to use it. It results in the same error. So, it is not meson specific.

cd ~/cpp_tests
source .venv/bin/activate
git clone https://github.com/pytorch/extension-cpp.git
cd extension-cpp
CC=/usr/bin/gcc CXX=/usr/bin/g++ python -m build --no-isolation -Cbuild-dir=build
pip install dist/cpp_extension-0.0.1-cp313-cp313-linux_x86_64.whl
cd
python
>>>import torch
>>>import extension_cpp

Results in the same error.

[bumi001]

running nm -AC _C.cpython-313-x86_64-linux-gnu.so shows
_C.cpython-313-x86_64-linux-gnu.so: U torch::Library::Library(torch::Library::Kind, std::string, std::optionalc10::DispatchKey, char const*, unsigned int)

DispatchKey is defined in site-packages/torch/include/c10/core/DispatchKey.h.

DispatchKey.h is included in site-packages/torch/include/torch/library.h.

library.h is included in extension_cpp/csrc/muladd.cpp.

The macro TORCH_LIBRARY is also defined in library.h.

So, I am not sure why we are getting the undefined symbol.

[bumi001]

I think I found the reason for the undefined symbol. First, in site_packages/extension_cpp, I used nm to find:

site-packages/extension_cpp$ nm -u --demangle _C.cpython-313-x86_64-linux-gnu.so | grep DispatchKey | grep -v Guard
                 U torch::Library::Library(torch::Library::Kind, std::string, std::optional<c10::DispatchKey>, char const*, unsigned int)

Then, in site_packages/torch/lib, I used nm to find:

site-packages/torch/lib$ nm -a --demangle * | grep 'torch::Library::Library'
nm: libgomp.so.1: no symbols
00000000018eebd0 T torch::Library::Library(torch::Library::Kind, std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> >, std::optional<c10::DispatchKey>, char const*, unsigned int)
00000000018eebd0 T torch::Library::Library(torch::Library::Kind, std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> >, std::optional<c10::DispatchKey>, char const*, unsigned int)
0000000000ec5c72 t torch::Library::Library(torch::Library::Kind, std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> >, std::optional<c10::DispatchKey>, char const*, unsigned int) [clone .cold]
                 U torch::Library::Library(torch::Library::Kind, std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> >, std::optional<c10::DispatchKey>, char const*, unsigned int)
                 U torch::Library::Library(torch::Library::Kind, std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> >, std::optional<c10::DispatchKey>, char const*, unsigned int)

It appears that the second parameter, std::string, in the constructor call in extension_cpp/_C.cpython-313-x86_64-linux-gnu.so is not resolving to std::__cxx11::basic_string<char, std::char_traits, std::allocator > in torch/lib/libtorch_cpu.so or torch/lib/libtorch_cuda.so or in torch/lib/libtorch_python.so.