Python package build fails with --cpp_implementation on ARM

[jskang94]

What version of protobuf and what language are you using?
Version: 3.6.1
Language: Python3

What operating system (Linux, Windows, ...) and version?
QEMU-emulated ARM docker image (on x86 linux host). resin/raspberrypi3-python:3.7-stretch

What runtime / compiler are you using (e.g., python version or gcc version)

$ python --version
Python 3.7.0

$ gcc --version
gcc (Raspbian 6.3.0-18+rpi1+deb9u1) 6.3.0 20170516
Copyright (C) 2016 Free Software Foundation, Inc.
This is free software; see the source for copying conditions.  There is NO
warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.

What did you do?
I downloaded protobuf 3.6.1 and tried to build Python package.

$ wget -O protobuf.tar.gz https://github.com/protocolbuffers/protobuf/releases/download/v3.6.1/protobuf-python-3.6.1.tar.gz && tar xvf protobuf.tar.gz
$ cd protobuf-3.6.1
$ ./autogen.sh && ./configure
$ make && make install && ldconfig
$ cd python
$ python setup.py build --cpp_implementation

But this fails with

running build_ext
building 'google.protobuf.pyext._message' extension
creating build/temp.linux-armv7l-3.7
creating build/temp.linux-armv7l-3.7/google
creating build/temp.linux-armv7l-3.7/google/protobuf
creating build/temp.linux-armv7l-3.7/google/protobuf/pyext
gcc -pthread -Wno-unused-result -Wsign-compare -DNDEBUG -g -fwrapv -O3 -Wall -fPIC -I. -I../src -I/usr/local/include/python3.7m -c google/protobuf/pyext/message_factory.cc -o build/temp.linux-armv7l-3.7/google/protobuf/pyext/message_factory.o -Wno-write-strings -Wno-invalid-offsetof -Wno-sign-compare
gcc -pthread -Wno-unused-result -Wsign-compare -DNDEBUG -g -fwrapv -O3 -Wall -fPIC -I. -I../src -I/usr/local/include/python3.7m -c google/protobuf/pyext/extension_dict.cc -o build/temp.linux-armv7l-3.7/google/protobuf/pyext/extension_dict.o -Wno-write-strings -Wno-invalid-offsetof -Wno-sign-compare
google/protobuf/pyext/extension_dict.cc: In function ‘PyObject* google::protobuf::python::extension_dict::_FindExtensionByName(google::protobuf::python::ExtensionDict*, PyObject*)’:
google/protobuf/pyext/extension_dict.cc:56:45: error: invalid conversion from ‘const char*’ to ‘char*’ [-fpermissive]
        ((*(charpp) = PyUnicode_AsUTF8AndSize(ob, (sizep))) == NULL? -1: 0): \
                      ~~~~~~~~~~~~~~~~~~~~~~~^~~~~~~~~~~~~
google/protobuf/pyext/extension_dict.cc:184:7: note: in expansion of macro ‘PyString_AsStringAndSize’
   if (PyString_AsStringAndSize(arg, &name, &name_size) < 0) {
       ^~~~~~~~~~~~~~~~~~~~~~~~
error: command 'gcc' failed with exit status 1

You can try with this dockerfile.

FROM resin/raspberrypi3-python:3.7-stretch
WORKDIR /root

RUN apt-get update \
    && apt-get install -y \
        automake libtool libtool-bin \
    && wget https://github.com/protocolbuffers/protobuf/releases/download/v3.6.1/protobuf-python-3.6.1.tar.gz \
        -O protobuf.tar.gz \
    && tar xvf protobuf.tar.gz \
    && rm protobuf.tar.gz \
    && cd protobuf-3.6.1 \
    && ./autogen.sh && ./configure \
    && make -j`grep -c ^processor /proc/cpuinfo` && make install \
    && ldconfig \
    && cd python \
    && python setup.py build --cpp_implementation \
    && python setup.py install \
    && cd /root \
    && rm -rf /root/protobuf-3.6.1 \
    && apt-get autoremove -y \
        automake libtool libtool-bin \
    && apt-get clean \
    && rm -rf /var/lib/apt/lists/*

What did you expect to see
Python protobuf package with --cpp_implementation

What did you see instead?
Build failure.

[acozzette]

This is an issue that's new with Python 3.7. #4862 fixes it on master but we need to create a new release with that fix.

[jskang94]

3.6.1.2 seems to be okay now. thanks!