embedded windows interpreter crashes on exit if external module loaded

[sheinb]

I've built a multiplatform app with an embedded scoped python interpreter using pybind11. In this app, py::exec is called (using an embedded TCL interpreter) while the interpreter is alive and I load a module built with pybind11. This seems to work, but if I execute a command from that loaded module (e.g. the add function in example.cpp) and then exit my main app, it crashes under Windows (32 and 64 bit). No errors under Mac OSX. Are there special requirements for closing down the interpreter I should be following?

Thanks,
David Sheinberg

[sheinb]

Upon further testing, I realize that the crash on exit (on windows) happens for modules that are loaded into the embedded interpreter that are themselves compiled as modules using pybind11. If I import other modules from the standard python lib (or numpy, e.g.) then I don't see the error. Just loading the module also doesn't cause the crash on exit, but if a function within the module is called, the host program will consistently crash on exit.

[jagerman]

Are you testing with current master? There's a fix in there (#1092) that might be related.

[sheinb]

Yes, I'm using the current master. I only see the problem on Windows, though - works fine on MacOS and Linux. Maybe #1092 fixed for most, but not all, compilers?

[jagerman]

No, the #1092 fix would have worked everywhere.

Can put you together a minimal example--i.e. the stripped down embedded code plus a stripped down module--where the issue still occurs, and I'll take a look.

[jagerman]

(It could also expose something that isn't right in your code, as well, but will be helpful either way).

[sheinb]

I can try to strip down and post (and replicate). Certainly could be an error in my code, but I'm actually only using about three pybind11 functions.

I did verify that if, instead of using the scoped_interpreter, I initialize_interpreter(), load a module and call a function in it, and exit the app without calling finalize_interpreter() then I get no error (of course it isn't a clean exit, so not ideal). If I add finalize_interpreter(), though, before leaving main, it causes the error.

[sheinb]

Argh...with a bit of depends.exe exploration, I realized the problem is due to a mismatch between the runtime dlls (debug vs release). I need to make sure the pybind11 modules are compiled for Release. Not really a problem with pybind11, but might be worth pointing out the "gotcha" for would be windows users (same gotcha that always applies, of course...). Sorry for wasted bandwidth.

[sheinb]

Perhaps to close the thread, I'll confirm that everything seems good with pybind11 (thank you!). In the end, the key was building my cmake nmake makefiles properly, to match my main app into which the modules I was building would be loaded:

cmake .. -G "NMake Makefiles" -DCMAKE_BUILD_TYPE=Release