[zeromq-dev] Building on Windows

[Michael Greene]

Martin, and all,

> Currently, there are 3 build systems in 0MQ because of Win32: MSVC
> project, CMake and MinGW. We cannot maintain all three of them
> Maintaining all 3 of them would be too much work with too little added
> value for us. Thus, we would like to choose one to maintain.

Is this really the breakdown?  I think it is closer to this:

1) Autotools can build on Cygwin on Windows using GCC and optionally MinGW.
2) MSVC can build on vanilla Window using itself.
3) CMake can build using either Cygwin or Vanilla windows, generating
makefiles or project files for either environment.  The actual
builders would be MinGW / MSVC.

I think the options are either:
* Only (1), requiring a dependency on Cygwin/MinGW to develop on Windows
* (1) and (2), requiring maintenance of two separate build environments
* (3), off-loading the maintenance of the two environments to an
external project, but adding a dependency on that project.

> 2. Ideally, there should be only one build system which would mean that
> MSVC proj is not an option as it doesn't work for non-Windows systems.

This is true in the ideal case.  However, unfortunately I don't know
of a many-language project for which this works.  Consider the case of
(eventual) Ruby and .NET libraries.  Ruby extensions explicitly cannot
be compiled on Visual C++ 2008.  .NET libraries must be compiled using
Visual Studio or Mono.

> 3. CMake is able to generate MSVC project files (am I right?)
> 3. Windows developers may be have little experience with anything aside
> MSVC and say MinGW may be considered to be an entry barrier to high to
> overcome.

I have seen this to be true on Thrift, a project that is incubating at
Apache.  Frequently, new users/developers there complain about the
difficulty setting up a build environment on Windows as it does not
compile under Visual C++.  There are two reasons I think this might be
less of a hindrance for 0MQ:
* Releases are more frequent for 0MQ, and you suggest distribution of
Windows binaries will be done in the future.  Thrift is currently not
producing binaries, and I think many of the complaints on the Thrift
mailing lists are from "users" more than "contributors."
* If CMake can in fact generate MSVC project files the casual Windows
contributor would probably be satisfied.  I am unfamiliar with CMake.

> 4. There may be performance difference between MSVC and gcc (MinGW) build.

I have seen this to be the case, but would personally be willing to
put up with the performance penalty on a build if there were logical
reasons.  With other projects the difference has been something like
2x-3x slower with MinGW.

The performance difference of the resulting binaries would have to be
measured with 0MQ.  It can go both ways.

> 5. MinGW may require additional dependencies on runtime (is it so?)

This does not have to be the case, no.  MinGW running under Cygwin
must be told via the -mno-cygwin flag to cross-compile and not depend
on Cygwin, but that is easy to setup.

I haven't really voted, but these are my opinions on the matter.
CMake or another next-generation builder (SCons/Waf?) does seem like
the ideal choice, but I have not used it in the past and can't testify
to its claims.

Michael