windows: boost::python reinitializes itself with the wrong version

[xobs]

I'm still trying to track this down, but I'll need to switch projects for a few weeks so I'd like to document this here.

When building nextpnr-ice40 on MSVC, it appears to include two different versions of Python. This is likely the reason why static builds crash whenever invoking a python script.

For example, if I build the Debug version of nextpnr-ice40, attach a debugger, and let it crash, we can see that it's crashing somewhere in libboost:

 	python37.dll!00007ffb938b2faf()	Unknown
>	boost_python37-vc142-mt-gd-x64-1_70.dll!boost::python::detail::init_module(PyModuleDef & moduledef, void(*)() init_function) Line 43	C++
 	nextpnr-ice40.exe!PyInit_nextpnrpy_ice40() Line 93	C++
 	python37_d.dll!_imp_create_builtin(_object * module, _object * spec) Line 1197	C
 	python37_d.dll!_PyMethodDef_RawFastCallDict(PyMethodDef * method, _object * self, _object * const * args, __int64 nargs, _object * kwargs) Line 497	C
 	python37_d.dll!_PyCFunction_FastCallDict(_object * func, _object * const * args, __int64 nargs, _object * kwargs) Line 582	C
 	python37_d.dll!PyCFunction_Call(_object * func, _object * args, _object * kwargs) Line 792	C
 	python37_d.dll!do_call_core(_object * func, _object * callargs, _object * kwdict) Line 4641	C
 	python37_d.dll!_PyEval_EvalFrameDefault(_frame * f, int throwflag) Line 3192	C
 	python37_d.dll!_PyEval_EvalCodeWithName(_object * _co, _object * globals, _object * locals, _object * const * args, __int64 argcount, _object * const * kwnames, _object * const * kwargs, __int64 kwcount, int kwstep, _object * const * defs, __int64 defcount, _object * kwdefs, _object * closure, _object * name, _object * qualname) Line 3930	C
 	python37_d.dll!_PyFunction_FastCallKeywords(_object * func, _object * const * stack, __int64 nargs, _object * kwnames) Line 440	C
 	python37_d.dll!call_function(_object * * * pp_stack, __int64 oparg, _object * kwnames) Line 4617	C
 	python37_d.dll!_PyEval_EvalFrameDefault(_frame * f, int throwflag) Line 3125	C
 	python37_d.dll!function_code_fastcall(PyCodeObject * co, _object * const * args, __int64 nargs, _object * globals) Line 283	C
 	python37_d.dll!_PyFunction_FastCallKeywords(_object * func, _object * const * stack, __int64 nargs, _object * kwnames) Line 408	C
 	python37_d.dll!call_function(_object * * * pp_stack, __int64 oparg, _object * kwnames) Line 4617	C
 	python37_d.dll!_PyEval_EvalFrameDefault(_frame * f, int throwflag) Line 3095	C
 	python37_d.dll!function_code_fastcall(PyCodeObject * co, _object * const * args, __int64 nargs, _object * globals) Line 283	C
 	python37_d.dll!_PyFunction_FastCallKeywords(_object * func, _object * const * stack, __int64 nargs, _object * kwnames) Line 408	C
 	python37_d.dll!call_function(_object * * * pp_stack, __int64 oparg, _object * kwnames) Line 4617	C
 	python37_d.dll!_PyEval_EvalFrameDefault(_frame * f, int throwflag) Line 3125	C
 	python37_d.dll!function_code_fastcall(PyCodeObject * co, _object * const * args, __int64 nargs, _object * globals) Line 283	C
 	python37_d.dll!_PyFunction_FastCallKeywords(_object * func, _object * const * stack, __int64 nargs, _object * kwnames) Line 408	C
 	python37_d.dll!call_function(_object * * * pp_stack, __int64 oparg, _object * kwnames) Line 4617	C
 	python37_d.dll!_PyEval_EvalFrameDefault(_frame * f, int throwflag) Line 3125	C
 	python37_d.dll!function_code_fastcall(PyCodeObject * co, _object * const * args, __int64 nargs, _object * globals) Line 283	C
 	python37_d.dll!_PyFunction_FastCallKeywords(_object * func, _object * const * stack, __int64 nargs, _object * kwnames) Line 408	C
 	python37_d.dll!call_function(_object * * * pp_stack, __int64 oparg, _object * kwnames) Line 4617	C
 	python37_d.dll!_PyEval_EvalFrameDefault(_frame * f, int throwflag) Line 3125	C
 	python37_d.dll!function_code_fastcall(PyCodeObject * co, _object * const * args, __int64 nargs, _object * globals) Line 283	C
 	python37_d.dll!_PyFunction_FastCallDict(_object * func, _object * const * args, __int64 nargs, _object * kwargs) Line 322	C
 	python37_d.dll!_PyObject_FastCallDict(_object * callable, _object * const * args, __int64 nargs, _object * kwargs) Line 98	C
 	python37_d.dll!object_vacall(_object * callable, char * vargs) Line 1198	C
 	python37_d.dll!_PyObject_CallMethodIdObjArgs(_object * obj, _Py_Identifier * name, ...) Line 1248	C
 	python37_d.dll!import_find_and_load(_object * abs_name) Line 1646	C
 	python37_d.dll!PyImport_ImportModuleLevelObject(_object * name, _object * globals, _object * locals, _object * fromlist, int level) Line 1754	C
 	python37_d.dll!builtin___import__(_object * self, _object * args, _object * kwds) Line 314	C
 	python37_d.dll!_PyMethodDef_RawFastCallDict(PyMethodDef * method, _object * self, _object * const * args, __int64 nargs, _object * kwargs) Line 515	C
 	python37_d.dll!_PyCFunction_FastCallDict(_object * func, _object * const * args, __int64 nargs, _object * kwargs) Line 582	C
 	python37_d.dll!_PyObject_FastCallDict(_object * callable, _object * const * args, __int64 nargs, _object * kwargs) Line 101	C
 	python37_d.dll!_PyObject_CallFunctionVa(_object * callable, const char * format, char * va, int is_size_t) Line 957	C
 	python37_d.dll!PyObject_CallFunction(_object * callable, const char * format, ...) Line 977	C
 	python37_d.dll!PyImport_Import(_object * module_name) Line 1936	C
 	python37_d.dll!PyImport_ImportModule(const char * name) Line 1390	C
 	nextpnr-ice40.exe!nextpnr_ice40::init_python(const char * executable, bool first) Line 252	C++
 	nextpnr-ice40.exe!nextpnr_ice40::CommandHandler::executeMain(std::unique_ptr<nextpnr_ice40::Context,std::default_delete<nextpnr_ice40::Context> > ctx) Line 292	C++
 	nextpnr-ice40.exe!nextpnr_ice40::CommandHandler::exec() Line 383	C++
 	nextpnr-ice40.exe!main(int argc, char * * argv) Line 233	C++
 	[External Code]	

Of note is that nextpnr-ice40.exe is calling into python37_d.dll (the debug version of the library), which then calls into nextpnr-ice40.exe, which then calls into boost, which finally calls into python37.dll (the non-debug version).

This may be related to microsoft/vcpkg#5097 which is an open issue, but as of right now it is not possible to build Python support into a static executable on Windows.

[mmicko]

Yes, this is existing bug. Debug build with VS did not work previously as well due to this bug. But you should not have issues with Release builds.