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I tried to link pybind11 with a static library. The building process was successful, but I got the runtime error "ImportError: undefined symbol". Directly linking with .o file worked fine though.

I have no luck with shared libraries either, with the same error. For shared libraries, I moved libadd.so to /usr/lib.

An example with a static library is as follows:

/* my_add.cpp */
#include <pybind11/pybind11.h>
#include "add.hpp"

namespace py = pybind11;

PYBIND11_MODULE(my_add, m) {
    m.def("add", &add);
}

/* add.hpp */
int add(int x, int y);

/* add.cpp */
#include "add.hpp"

int add(int x, int y) {
    return x + y;
}

First, I complied add.cpp into a static library.

g++ -c add.cpp -o add.o
ar rcs libadd.a add.o

Then, I complied my_add.cpp and linked it against libadd.a.

g++ -Wall -shared -std=c++11 -fPIC $(python3 -m pybind11 --includes) libadd.a my_add.cpp -o my_add$(python3-config --extension-suffix)

In the same directory:

$ python3
Python 3.10.12 (main, Jun 11 2023, 05:26:28) [GCC 11.4.0] on linux
Type "help", "copyright", "credits" or "license" for more information.
>>> import my_add
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
ImportError: /working_directory/my_add.cpython-310-x86_64-linux-gnu.so: undefined symbol: _Z3addii

On the other hand, if I built with

g++ -Wall -shared -std=c++11 -fPIC $(python3 -m pybind11 --includes) add.o my_add.cpp -o my_add$(python3-config --extension-suffix)

then everything worked fine.

I'd really appreciate it if anyone could help.

chrt
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1 Answers1

1

I found the answer here: undefined symbol using pybind11 cmd

This is not really a pybind11-specific problem but a C/C++ problem.

All those linker flags should come after the cpp that needs them.

In my case, swapping "libadd.a" and "my_add.cpp" solves the issue.

My question can be marked as a duplication. Thanks.

chrt
  • 21
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