[zeromq-dev] Porting libzmq to C++11

Aram Santogidis aram.santogidis at cern.ch
Thu May 18 10:57:16 CEST 2017


a good reason to modernize the codebase, or even better to create a new 
project ala libzmq11, is to help its evolution with new networking 
technologies and software engineering practices.

As an example, consider the difficulties many faced (including myself) 
in extending ZeroMQ to support RDMA-based networking interfaces. The 
current design and implementation is hostile to such extensions. 
Honestly, C++98 or not, I think it still can be done but with major cost 
in development effort and additional complexity to an already complex 

Moving to C++11 and beyond is not merely an argument of fashion, as some 
of you implied, but it is vital for its future.
C++ and related technologies evolve and libzmq stays behind. New 
developers are reluctant to contribute once they have a look at the 
current design and implementation (old school C++ roughly speaking).

Think for example when networking will be included in the standard, how 
much ugly code that juggles platform differences could be eliminated 
from the current implementation. Same applies for threading, which is in 
the standard since C++11.

I don't underestimate the importance (and the size?) of the current 
userbase. I'm aware from first-hand experience about some fairly 
critical software that relies on libzmq.

I guess the idea is to create i) a new project in the ZeroMQ 
organization that ii) implements ZMTP and iii) the non-depricated ZMQ 
socket types. The public API of libzmq should be a subset of the 
libzmq11 so that will facilitate the transition of users, in the long 
term, that do not run on legacy systems.

I will happily contribute to such an effort provided that there will be 
at least one or two experienced members from the community that will 
join this effort.


On 17.05.2017 16:54, BJovke . wrote:
> Well, you're right. There must be a good reason for such an undertaking.
> I too feel that C++11 itself is not good enough reason.
> Anyway there has to be enough people willing to contribute to it.
> I was just saying this because no idea should be discarded right away,
> but for sure there needs to be a valid need and reason for it.
> Greetings.
> 2017-05-17 16:15 GMT+02:00 Doron Somech <somdoron at gmail.com
> <mailto:somdoron at gmail.com>>:
>     What will be the benefit from moving to C++11? And more important
>     what is the benefit from having two projects? one supporting C++11
>     and one not?
>     I think that maintaining two repositories is hard and not sure for
>     what cause?
>     Anyway, if some one want to do it, in the zeromq philosophy, please
>     fork and add the project to the zeromq organization.
>     On Wed, May 17, 2017 at 4:29 PM, <lists at chuckremes.com
>     <mailto:lists at chuckremes.com>> wrote:
>         > On May 17, 2017, at 7:56 AM, BJovke . <bjovan at gmail.com <mailto:bjovan at gmail.com>> wrote:
>         >
>         > Hello.
>         >
>         > Libzmq is not even fully C++ compliant:
>         >   - There's no exception handling.
>         >   - There are no RAII principles implemented.
>         >   - Parent/child object hierarchy is loose or not implemented, all of the burden of proper order of calls is on programmer.
>         >
>         > And so on...
>         >
>         > C++11 is really a remarkable feat of engineering and me personally like to see fully C++11 implemented software.
>         > Unfortunately, for libzmq this would require substantial rewrite of the library.
>         >
>         > Maybe there's an option to create another parallel branch to existing libzmq or even create another product, for example "libzmq11"?
>         > On the wire this could be 100% compatible with non-C++11 libzmq but there would be 0% chance to compile older projects with it.
>         This is a good time to bring out some old blog posts. Martin
>         Sustrik was the original developer of libzmq. He had some
>         thoughts on why he should have written the library in C instead
>         of C++. Here you go:
>         http://250bpm.com/blog:4
>         http://250bpm.com/blog:8
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> --
> Jovan Bunjevački.
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