I solved this. It did require the Python caller obtaining the string size from the C++ DLL. The key part is to use ctypes.string_at() to then define the string at the Python end.
lib.fun.argtypes = [c_void_p, c_void_p] lib.fun.restype = c_void_p size = c_int() return_ptr = lib.fun(self.obj, byref(size)) cstring = string_at(return_ptr, size) On Wednesday, October 14, 2020 at 7:17:35 PM UTC-5 acoz...@google.com wrote: > I think if you have to work with C types then you will need to provide > both a char* and an integer length. That Python error makes it sound like > the Python code is probably trying to parse beyond the end of the > serialized message. > > On Wed, Oct 14, 2020 at 3:55 PM Randy Nuss <randal...@gmail.com> wrote: > >> I am building a C++ library with protobuf messages for consumption by a >> Python program. The issue is SerializeToString() takes std::string, but >> only c_types (like char*) can be exported by the dll, which results in >> numerical zeros being recognized as string terminators and truncating the >> ParseFromString() process. >> >> I tried using SerializeToArray() but get the following error in Python: >> google.protobuf.message.DecodeError: Field number 0 is illegal. >> >> I would appreciate any suggestions. Thanks. >> >> -- >> You received this message because you are subscribed to the Google Groups >> "Protocol Buffers" group. >> To unsubscribe from this group and stop receiving emails from it, send an >> email to protobuf+u...@googlegroups.com. >> To view this discussion on the web visit >> https://groups.google.com/d/msgid/protobuf/9c3bf578-ba5b-4059-a64b-ec6731690a70n%40googlegroups.com >> >> <https://groups.google.com/d/msgid/protobuf/9c3bf578-ba5b-4059-a64b-ec6731690a70n%40googlegroups.com?utm_medium=email&utm_source=footer> >> . >> > -- You received this message because you are subscribed to the Google Groups "Protocol Buffers" group. To unsubscribe from this group and stop receiving emails from it, send an email to protobuf+unsubscr...@googlegroups.com. To view this discussion on the web visit https://groups.google.com/d/msgid/protobuf/93aab028-c827-48b2-b3f8-654650d112e2n%40googlegroups.com.
