passing string to a function is not working in 2.2.0

[prashant-saxena]

Hello,
Windows 10
Python 3.10.0
nanobind 2.2.0
VS 2022 17.11.4

#include <nanobind/nanobind.h>
#include <string>

namespace nb = nanobind;
using namespace nb::literals;

class PorterStemmer {
public:
    PorterStemmer() {}

    // Use std::string for compatibility with Python strings
    std::string stem(const std::string &input) {
        std::string output = input;
        std::reverse(output.begin(), output.end());
        return output;
    }
};

NB_MODULE(stemmer, m) {
    nb::class_<PorterStemmer>(m, "PorterStemmer")
        .def(nb::init<>())             // Expose the default constructor
        .def("stem", &PorterStemmer::stem,   // Expose the stem method
             "Stem a word");
}

No error while building the extension but when using it, there is an error

TypeError: stem(): incompatible function arguments. The following argument types are supported:
    1. stem(self, arg: std::basic_string<char,std::char_traits<char>,std::allocator<char> >, /) -> std::basic_string<char,std::char_traits<char>,std::allocator<char> >

Invoked with types: stemmer.PorterStemmer, str

Based on search, I have changed 'include' to this:

#include <nanobind/nanobind.h>
#include <nanobind/stl/string.h>

Now there is an error while building the extension ending with

build\stemmer\release\cp310-amd64-windows-msvc\stemmer.cp310-win_amd64.pyd : fatal error LNK1169: one or more multiply defined symbols found

[wjakob]

I have a suspicion that there is more going on here. The linker error message should have stated the name of the doubly defined symbol.

Can you create a PR to this repository (e.g. by modifying one of the builtin examples) that reproduces this problem? If it fails on the CI, that's something I could look into.

[prashant-saxena]

Hello @wjakob

This is the python script I'm using on windows to create nanobind static lib.

import os
from sysconfig import get_paths as gp
import glob
import nanobind

# Nanobind include
include1 = nanobind.include_dir()
# Nanobind's robin map include
include2 = os.path.join(include1.replace("include", ""), "ext", "robin_map", "include")
# Python include
include3 = gp()['include']

for name in glob.glob(os.path.join(include1.replace("include", ""), "src", "*.cpp")):
    print("Compiling...", name)
    # We don't need this
    if name.endswith("nb_combined.cpp"):
        continue
    os.system(f"cl /c /nologo /Ox /MD /std:c++17 /EHsc /I {include1} -I {include2} /I {include3} {name}")

os.system("lib *.obj /OUT:nanobind.lib")

After excluding "nb_combined.cpp", everything is working fine.

[wjakob]

If you use such custom build systems, you are on your own. Please review all the comments in nb_combined.cpp to know what you are getting into :-).