245 Exit Code when using bindings (Dog struct & bind_vector) in tutorial

[btakita]

I'm going through the https://nanobind.readthedocs.io/en/latest/exchanging.html portion of the tutorial. I tried adding bind_vector, but my Python program has a 245 exit code...after a ~2 second pause when existing the program. If I don't use the binding, the Python program exits quickly with a 0 exit code.

inference.cpp

#include <nanobind/nanobind.h>
#include <nanobind/stl/string.h>
#include <nanobind/stl/tuple.h>
#include <nanobind/stl/bind_vector.h>
// #include <nanobind/stl/vector.h>

namespace nb = nanobind;
using namespace nb::literals;
using IntVector = std::vector<int>;

struct Dog {
  std::string name;

  [[nodiscard]] std::string bark() const {
    return name + ": woof!";
  }
};

int add(int a, int b = 1) { return a + b; }

IntVector double_it(const IntVector &in) {
  IntVector out(in.size());
  for (size_t i = 0; i < in.size(); ++i) {
    out[i] = in[i] * 2;
  }
  return out;
}

int foo(int &in) {
  in *= 2;
  return std::sqrt(in);
}

NB_MODULE(inference, m) {
  m.def("double_it", &double_it);
  m.def("foo", [](int i) {
    int rv = foo(i);
    return std::make_tuple(rv, i);
  });

  // m.def("add", &add, "a"_a, "b"_a = 1,
  //       "This function adds two numbers and increments if only one is provided.");
  // m.attr("the_answer") = 42;
  // nb::class_<Dog>(m, "Dog")
  //     .def(nb::init<>())
  //     .def(nb::init<const std::string &>())
  //     .def("bark", &Dog::bark)
  //     .def_rw("name", &Dog::name)
  //     .def("__repr__", [](const Dog &p) {
  //       return "<inference.Dog named '" + p.name + "'>";
  //     })
  //     .def("bark_later", [](const Dog &p) {
  //       auto callback = [name = p.name] {
  //         nb::print(nb::str("{}: woof!").format(name));
  //       };
  //       return nb::cpp_function(callback);
  //     });
  nb::bind_vector<IntVector>(m, "IntVector");
}

cpp_test.py

import builddir.inference as inference


# print(inference.add(1))
# print(inference.the_answer)
# dog = inference.Dog("Max")
# print(dog)
# print(dog.name)
# dog.name = "Charlie"
# print(dog.bark())
# f = dog.bark_later()
# print(f)
# print(f())

print(inference.double_it([1, 2, 3]))
print(inference.foo(5))

print("DONE!")

Build

poe meson compile -C builddir
Poe => meson compile -C builddir
INFO: autodetecting backend as ninja
INFO: calculating backend command to run: /usr/bin/ninja -C /home/brian/work/project/builddir
ninja: Entering directory `/home/brian/work/project/builddir'
[2/2] Linking target inference.abi3.so

Run cpp_test.py

poe python -m cpp_test; echo $?
Poe => python3.12 -m cpp_test
245

I also had the same issue with the Dog struct.

#include <nanobind/nanobind.h>
#include <nanobind/stl/string.h>
#include <nanobind/stl/tuple.h>
// #include <nanobind/stl/bind_vector.h>
#include <nanobind/stl/vector.h>

namespace nb = nanobind;
using namespace nb::literals;
using IntVector = std::vector<int>;

struct Dog {
  std::string name;

  [[nodiscard]] std::string bark() const {
    return name + ": woof!";
  }
};

int add(int a, int b = 1) { return a + b; }

IntVector double_it(const IntVector &in) {
  IntVector out(in.size());
  for (size_t i = 0; i < in.size(); ++i) {
    out[i] = in[i] * 2;
  }
  return out;
}

int foo(int &in) {
  in *= 2;
  return std::sqrt(in);
}

NB_MODULE(inference, m) {
  // nb::bind_vector<IntVector>(m, "IntVector");
  m.def("double_it", &double_it);
  m.def("foo", [](int i) {
    int rv = foo(i);
    return std::make_tuple(rv, i);
  });

  m.def("add", &add, "a"_a, "b"_a = 1,
        "This function adds two numbers and increments if only one is provided.");
  m.attr("the_answer") = 42;
  nb::class_<Dog>(m, "Dog")
      .def(nb::init<>())
      .def(nb::init<const std::string &>())
      .def("bark", &Dog::bark)
      .def_rw("name", &Dog::name)
      .def("__repr__", [](const Dog &p) {
        return "<inference.Dog named '" + p.name + "'>";
      })
      .def("bark_later", [](const Dog &p) {
        auto callback = [name = p.name] {
          nb::print(nb::str("{}: woof!").format(name));
        };
        return nb::cpp_function(callback);
      });
}

import builddir.inference as inference


print(inference.add(1))
print(inference.the_answer)
dog = inference.Dog("Max")
print(dog)
print(dog.name)
dog.name = "Charlie"
print(dog.bark())
f = dog.bark_later()
print(f)
print(f())

print(inference.double_it([1, 2, 3]))
print(inference.foo(5))

print("DONE!")

Am I doing something wrong or is this a bug?

---

I tried https://nanobind.readthedocs.io/en/latest/ownership.html#unique-pointers with faulthandler.enable().

#include <nanobind/stl/unique_ptr.h>

namespace nb = nanobind;

struct Data { };

NB_MODULE(nb_data, m) {
    nb::class_<Data>(m, "Data");
    m.def("create", []() { return std::make_unique<Data>(); });
    m.def("consume", [](std::unique_ptr<Data> x) { /* no-op */ });
}

import faulthandler
faulthandler.enable()

from ext import nb_data

print("START")
# data = nb_data.create()
# print("MID")
# nb_data.consume(data)
print("DONE!")

clear; ./build.sh && poe python -m nb_data_test; echo $?
Poe => meson compile -C builddir
INFO: autodetecting backend as ninja
INFO: calculating backend command to run: /usr/bin/ninja -C /home/brian/work/project/builddir
ninja: Entering directory `/home/brian/work/project/builddir'
ninja: no work to do.
Poe => python3.12 -m nb_data_test
Fatal Python error: Segmentation fault

Current thread 0x0000746bfeb44b80 (most recent call first):
  File "<frozen importlib._bootstrap>", line 488 in _call_with_frames_removed
  File "<frozen importlib._bootstrap_external>", line 1293 in create_module
  File "<frozen importlib._bootstrap>", line 813 in module_from_spec
  File "<frozen importlib._bootstrap>", line 921 in _load_unlocked
  File "<frozen importlib._bootstrap>", line 1331 in _find_and_load_unlocked
  File "<frozen importlib._bootstrap>", line 1360 in _find_and_load
  File "<frozen importlib._bootstrap>", line 488 in _call_with_frames_removed
  File "<frozen importlib._bootstrap>", line 1415 in _handle_fromlist
  File "/home/brian/work/project/nb_data_test.py", line 4 in <module>
  File "<frozen runpy>", line 88 in _run_code
  File "<frozen runpy>", line 198 in _run_module_as_main
245

[btakita]

There's an issue with the Meson integration. I switched to CMake & it works.