pybind_set_argv.cpp

#if PY_VERSION_MAJOR >= 3
#define PYBIND11_ARGV_TYPE wchar_t**
#else
#define PYBIND11_ARGV_TYPE char**
#endif

struct wide_char_arg_deleter {
	void operator()(void* ptr) const {
#if PY_VERSION_HEX >= 0x030500f0
		// API docs: https://docs.python.org/3/c-api/sys.html#c.Py_DecodeLocale
		PyMem_RawFree(ptr);
#else
		delete ptr;
#endif
	}
};

wchar_t* widen_chars(char* safe_arg) {
#if PY_VERSION_HEX >= 0x030500f0
	wchar_t* widened_arg = Py_DecodeLocale(safe_arg, nullptr);
#elif HAVE_BROKEN_MBSTOWCS
	size_t count = strlen(safe_arg);
	widened_arg = nullptr;
	if (count != static_cast<size_t>(-1)) {
		widened_arg = new wchar_t[count + 1];
		mbstowcs(widened_arg, safe_arg, count + 1);
	}
#else
	size_t count = mbstowcs(nullptr, safe_arg, 0);
	widened_arg = nullptr;
	if (count != static_cast<size_t>(-1)) {
		widened_arg = new wchar_t[count + 1];
		mbstowcs(widened_arg, safe_arg, count + 1);
	}
#endif
	return widened_arg;
}

inline void set_interpreter_argv(int argc, char** argv, bool add_current_dir_to_path) {
    // Before it was special-cased in python 3.8, passing an empty or null argv
    // caused a segfault, so we have to reimplement the special case ourselves.
    char** safe_argv = argv;
    std::unique_ptr<char*[]> argv_guard;
    std::unique_ptr<char[]> argv_inner_guard;
    if (nullptr == argv || argc <= 0) {
        argv_guard = std::unique_ptr<char*[]>(safe_argv = new char*[1]);
        argv_inner_guard = std::unique_ptr<char[]>(safe_argv[0] = new char[1]);
        safe_argv[0][0] = '\0';
        argc = 1;
    }
#if PY_MAJOR_VERSION >= 3
    size_t argv_size = static_cast<size_t>(argc);
    // SetArgv* on python 3 takes wchar_t, so we have to convert.
    std::vector< std::unique_ptr<wchar_t[], wide_char_arg_deleter> > widened_argv_entries;
    for (size_t ii = 0; ii < argv_size; ++ii) {
	widened_argv_entries.emplace_back(widen_chars(safe_argv[ii]));
        if (widened_argv_entries.back()) {
            // A null here indicates a character-encoding failure or the python
            // interpreter out of memory. Give up.
            return;
        }
    }

    PYBIND11_ARGV_TYPE pysys_argv = widened_argv.get();
#else
    PYBIND11_ARGV_TYPE pysys_argv = safe_argv;
#endif

    PySys_SetArgv(argc, pysys_argv);
    if (!add_current_dir_to_path)
	PyList_PopItem(py::module::import("sys").attr("path").ptr(), 0);
}