pybind11 + pySide2 crashes

Hello

1st of all thanks for awesome lib!

2nd I'm stuck with this issue, most of my other code works fine but this one... wrhhh

So the layout
I have c++ app with Qt as gui, I use QtWebEngine to embed a code editor for easier coding, none of it is much relevant to use but just in case. I'll try to "lay out" what/why I'm doing as maybe Its affecting something...

Now I added a py::scoped_interpreter guard; in my python handling class in header. This is a persistent copy of python that is meant to live the entire time app is alive. So Its put in constructur and kicks off. The 1st command I send to pybind is to push the print statement out of it so the code is as follow >

#include "pythonHandler.h"
#include "iostream"
#include "qdebug.h"
#include "simpleWindow.h"
#include "testManager.h"
#include "lib/globalHandler.h"

#ifdef _LIBPATH
#define TXT _LIBPATH
#else
#define TXT "unconfiguredEnviPath"
#endif
int tadd(int i, int j) {
    std::cout << i << j << std::endl;
    return i + j;
}

PYBIND11_EMBEDDED_MODULE(pyt, m) {
    m.doc() = "I do Nothing... yet?";
    m.def("xadd", &tadd, "A function which adds two numbers");
    //m.def("getGlobalHelper", &tadd, "A function which adds two numbers"); // they should return pointer to objects with these objects functions exposed.
    //m.def("getTestManager", &tadd, "A function which adds two numbers"); // they should return pointer to objects with these objects functions exposed.
    m.def("getTestManager", &testManager::TM, py::return_value_policy::reference);
    m.def("getGlobalHelper", &globalHandler::getGlobalHelper, py::return_value_policy::reference);
}


PYBIND11_EMBEDDED_MODULE(icPrint, m) {
    // `m` is a `py::module` which is used to bind functions and classes
    m.doc() = "Print helper class  manager classes"; // optional module docstring
    m.def("print_overrided", [](std::string log) {
        auto resultLog = QString(log.data());
        if (resultLog.length() > 0 && resultLog != "\n")
            simpleWindow::SW()->setReturnMessage(resultLog);
    });
}


pythonHandler *pythonHandler::icP() {
    static pythonHandler icp;
    return &icp;
}

pythonHandler::pythonHandler() {
    //guard = py::scoped_interpreter{};
    glob = py::globals();
    //loc = py::object();

    QString starter(R"(
from  icPrint import print_overrided
import io, sys,os
class StdoutCatcher(io.TextIOBase):
    def __init__(self):
        self.data = []
    def write(self, stuff):
        print_overrided(stuff)
sys.stdout = StdoutCatcher()

default_value = "crap"
val = "$replacePathEnv"
print(val)

sys.path.insert(0, val)
sys.path.insert(0, val+"Lib")
sys.path.insert(0, val+"DLLs")
sys.path.insert(0, val+"lib\site-packages")
for a in sys.path:
    print(a)

if not hasattr(sys, 'argv'):
    sys.argv  = ['']
        )");
    QString envi(TXT);
    envi = envi + "python/active/";
    qDebug() << "Envi path : " << envi;
    std::cout << " envi path " << envi.toStdString().c_str() << std::endl;
    starter = starter.replace("$replacePathEnv", envi);
    try {
        py::exec(starter.toStdString().c_str(), glob);
    }
    catch (const std::exception &e) {
        QString error(e.what());
        simpleWindow::SW()->setReturnMessage(error);
    }
}

pythonHandler::~pythonHandler() {
}

void pythonHandler::runCommand(QString text) {

    try {
        py::exec(text.toStdString().c_str(), glob);
    }
    catch (const std::exception &e) {
        QString error(e.what());
        simpleWindow::SW()->setReturnMessage(error);
    }
}

So once the class is initialized it pushes out print back to c++ to be displayed in my editor and I send commands to it from editor. So far so good, I can send as much commands as I want provided I'm not working with pyside2. I did not check other libraries yet...

So the problem starts here, when I run this command >

from PySide2.QtWidgets import *
app = QApplication([""])
w = QWidget()
w.show()
sys.exit(app.exec_())

1st run is fine, but second run cause

And here I'm lost... what do I do with it ? :- )

One thing that I wonder about is if I should somehow pass my c++Qt QApplication instead of making new one? I'm not sure, at some point I'd like to make a widget in python that interacts with c++ widget so... hmmm ? ideas?

Regards
Dariusz

Start with the embedded interpreter lifecycle in pythonHandler::pythonHandler and runCommand, using the PySide2 command shown in the issue to reproduce the second-run crash. Inspect how the persistent interpreter and QApplication are created and reused; done means identifying a reproducible lifecycle cause and documenting the required ownership or usage change.