Make C++ implementation C++11 only.

[liujisi]

C++11 has been out for several years and we are thinking of moving to allow C++11 features from being used in the code base. That means the implementation will not be able to compile if you don't have a C++11 compiler.

We may create a branch that works for C++98. The branch will only accept bug fixes, but not new features, optimization, etc

Please reply in this thread if you think this would be an issue for your project.

[koubaa]

Hello,

Thank you for collecting feedback about this. My project consists of shared libraries on linux. Some libraries are built with c++11 and others must be built with c++98 (for compatibility with some other libraries). We link protobuf dynamically so this may not an issue for us, unless any c++11 language features will be used in header files that our c++98 libraries use.

[matthauck]

This would be an issue for our project. We support back to centos5 (gcc 4.1) and a number of platforms in between for which we are not yet able to turn on the c++11 flag. One of the attractive things about protobuf was its impressive backwards support, and would be sad to have older platforms be stuck with less.

[matthauck]

(PS. I feel bad saying this since I would love to move to c++11 only for our project too, haha! It is a sad world that we can't use "new" features from 6 years go yet. I'm sure libraries feel this pain more than applications do even. All of which to say, I feel your pain! 😭 )

[vjpai]

Hi there, we made a related decision in gRPC - version 1.0 supports older compilers with only limited C++11 support (not as few as protobuf, though), but version 1.1 and beyond only support true C++11 compilers (as of grpc/grpc#8602 ). I understand, though, that protobuf's predicament is greater since it is a package that has been public for much longer, has more users, and has been supporting C++98.

[gerben-s]

I strongly favor moving to a 4.x C++11 only branch. Users tight to pre-c++11 can continue using the 3.x branch which we support in maintenance mode.

Note that linking pre-c++11 and post-c++11 libraries is already very tricky due to the standard libraries being slightly incompatible (see https://gcc.gnu.org/wiki/Cxx11AbiCompatibility). Hence I think the impact of not being able to link libs depending on pre-c++11 and post-c++11 proto runtime is minor, given you already have dangerous issues lurking around.

Furthermore, for c++ protos, we already have the rule that all proto files in a binary have to be compiled with the exact same version of the compiler and runtime.

[os12]

We have C++14 enabled at work so this change would be welcome. Protobuf has great compatibility w.r.t. the serialized format, so people who are stuck with old environments can continue using the old libs.

[daomuzhiwang]

Hello all,

Now I'm using gcc-5.4.0 to compile protobuf. However it couldn't be built because of C++11 new features.
I tried to modify "Makefile" to add compile options "-std=c++11" into "CXXFLAGS", but it still didn't work. How could I make it?

Solution:

I used command "configure CXXFLAGS=-std=c++11" to config protobuf.

+1 , backporting gcc5.4.x /7.x on old unmaintained distros is straightforward also with proper stripping unneeded language target at configure build flag.

[jakirkham]

Requiring C++11 will make it basically impossible to support protobuf on some Python versions on Windows. In particular, Python 2.7 support will not be possible and Python 3.5 will need to be a minimum requirement. This is assuming that protobuf continues to need to have compiled portions for these Python versions. The reason being that CPython ties each major minor version of the interpreter to a particular Visual Studio version on Windows. As a result, any extension one builds needs to be built with the same runtime as the interpreter or risk segfaults. A full listing can be found in this reference. Note that Python 2.6 and 2.7 requires Visual Studio 2008 (VC 9), which does not have C++11 support. Also Python 3.4 requires Visual Studio 2010 (VC 10), which also does not have C++11 support. Only Python 3.5 and 3.6, which requires Visual Studio 2015 (VC 14), have C++11 support.

cc @xfxyjwf

[os12]

With respect to @jakirkham's note, Python does not let people build their recent recent releases with older Visual Studio versions. IMO Protobuf should follow suit. There will be no way to move forward otherwise.

Also note that Visual Studio 2010 has basic C++11 support, see the official reference.