IMHO the issue lies somewhere else.
I suspect that you are using an uninitialized pointer or going out of bounds.
Without being provided a minimal reproduceable code, I tried to come up with something on my own. I am leaving the sources below for reference. During my testing, everything worked as expected on Windows (with MSVC and Clang). Modifying the array elements in Python showed up in the C++ code. Reassigning the variables in Python and calling the garbage collector manually did not invalidate the C++ class. When removing keep_alive (and multiplying the arrays with 2 at init_ptrs), I also managed to see the same memory being reassigned to the newly initialized array.
Sources
test.py
import torch
import numpy as np
import gc
import foo
if __name__ == "__main__":
gc.disable()
my_array = np.array([0, 1, 2, 3], dtype=np.int32)
my_tensor = torch.tensor([4, 5, 6, 7], dtype=torch.float32)
my_foo = foo.Foo()
my_foo.init_ptrs(my_array * 2, my_tensor.numpy() * 2)
print(gc.get_count())
gc.collect()
print(gc.get_count())
my_foo.do_something_with_ptrs()
my_array[0] = 71
my_tensor[0] = 72
my_foo.do_something_with_ptrs()
my_array = np.array([10, 11, 12, 13], dtype=np.int32)
my_tensor = torch.tensor([14, 15, 16, 17], dtype=torch.float)
print(gc.get_count())
gc.collect()
print(gc.get_count())
my_foo.do_something_with_ptrs()
del(my_foo)
print(gc.get_count())
gc.collect()
print(gc.get_count())
foo.cpp
#include <pybind11/pybind11.h>
#include <pybind11/numpy.h>
#include <iostream>
namespace py = pybind11;
class Foo
{
public:
void initPtrs(py::array_t<int32_t, py::array::c_style> pyAryA,
py::array_t<float_t, py::array::c_style> pyAryB)
{
auto buffer_info = pyAryA.request();
m_ptrA = static_cast<int32_t *>(buffer_info.ptr);
m_sizeA = [&]
{
size_t sum = 0;
for (auto elem : buffer_info.shape)
sum += elem;
return sum;
}();
std::cout << "Initialized int32 with size: " << m_sizeA << '\n';
buffer_info = pyAryB.request();
m_ptrB = static_cast<float_t *>(buffer_info.ptr);
m_sizeB = [&]
{
size_t sum = 0;
for (auto elem : buffer_info.shape)
sum += elem;
return sum;
}();
std::cout << "Initialized float with size: " << m_sizeB << '\n';
}
void doSomethingWithPtrs()
{
std::cout << "int32 idx 0: ";
for (size_t i = 0; i < m_sizeA /*+ 1*/; ++i)
{
std::cout << ' ' << m_ptrA[i];
}
std::cout << '\n';
std::cout << "float idx 0: ";
for (size_t i = 0; i < m_sizeB /*+ 1*/; ++i)
{
std::cout << ' ' << m_ptrB[i];
}
std::cout << '\n';
}
private:
int32_t *m_ptrA = nullptr;
size_t m_sizeA = 0;
float_t *m_ptrB = nullptr;
size_t m_sizeB = 0;
};
PYBIND11_MODULE(foo, m)
{
py::class_<Foo>(m, "Foo")
.def(py::init<>())
.def("init_ptrs", &Foo::initPtrs, py::keep_alive<1, 2>(), py::keep_alive<1, 3>())
.def("do_something_with_ptrs", &Foo::doSomethingWithPtrs);
}
setup.py (based on CMake example)
import os
import re
import sys
import platform
import subprocess
from setuptools import setup, Extension
from setuptools.command.build_ext import build_ext
from distutils.version import LooseVersion
class CMakeExtension(Extension):
def __init__(self, name, sourcedir=''):
Extension.__init__(self, name, sources=[])
self.sourcedir = os.path.abspath(sourcedir)
class CMakeBuild(build_ext):
def run(self):
try:
out = subprocess.check_output(['cmake', '--version'])
except OSError:
raise RuntimeError("CMake must be installed to build the following extensions: " +
", ".join(e.name for e in self.extensions))
cmake_version = LooseVersion(
re.search(r'version\s*([\d.]+)', out.decode()).group(1))
if cmake_version < '3.11.0':
raise RuntimeError("CMake >= 3.11.0 required")
for ext in self.extensions:
self.build_extension(ext)
def build_extension(self, ext):
extdir = os.path.abspath(os.path.dirname(
self.get_ext_fullpath(ext.name)))
# required for auto-detection of auxiliary "native" libs
if not extdir.endswith(os.path.sep):
extdir += os.path.sep
cmake_args = ['-DCMAKE_LIBRARY_OUTPUT_DIRECTORY=' + extdir,
'-DPYTHON_EXECUTABLE=' + sys.executable,
'-DPIP_INSTALL=ON',
]
cfg = 'Debug' if self.debug else 'Release'
build_args = ['--config', cfg]
if platform.system() == "Windows":
cmake_args += [
'-DCMAKE_LIBRARY_OUTPUT_DIRECTORY_{}={}'.format(cfg.upper(), extdir)]
if sys.maxsize > 2**32:
cmake_args += ['-A', 'x64']
build_args += ['--', '/m']
else:
cmake_args += ['-DCMAKE_BUILD_TYPE=' + cfg]
build_args += ['--', '-j10']
env = os.environ.copy()
env['CXXFLAGS'] = '{} -DVERSION_INFO=\\"{}\\"'.format(env.get('CXXFLAGS', ''),
self.distribution.get_version())
if not os.path.exists(self.build_temp):
os.makedirs(self.build_temp)
subprocess.check_call(['cmake', ext.sourcedir] +
cmake_args, cwd=self.build_temp, env=env)
subprocess.check_call(['cmake', '--build', '.'] +
build_args, cwd=self.build_temp)
setup(
name='Foo',
version=2022.08,
# The list of python packages
py_modules=['foo'],
package_dir={'': os.path.join(os.getcwd())},
# A list of instances of setuptools.Extension providing the list of Python extensions to be built.
ext_modules=[CMakeExtension('foo')],
# A dictionary providing a mapping of command names to Command subclasses.
cmdclass=dict(build_ext=CMakeBuild),
zip_safe=False
)
CMakeLists.txt
cmake_minimum_required(VERSION 3.5)
project(Foo)
include(FetchContent)
# Fetch pybind11
FetchContent_Declare(
pybind11
GIT_REPOSITORY https://github.com/pybind/pybind11
GIT_TAG v2.9.1
)
FetchContent_MakeAvailable(pybind11)
pybind11_add_module(foo "")
target_sources(foo
PUBLIC
${CMAKE_CURRENT_LIST_DIR}/foo.cpp
)
