[Dune-devel] CMake with Visual Studion/Windows

[Christoph Grüninger]

Hello my dear CMake friend,
recently I gave Windows a try and tried to compile Dune with 
Visual Studio and CMake.

== Setup ==
- Windows 7
- Visual Studio 2013 Express (free/non-commercial version), 
aka Microsoft's C++ compiler
- CMake 3.0
- Dune's master branch from July 2014

== Summary ==
- CMake works in general, thus I was not able to execute any 
Dune program
- Interplay with Visual Studio (VS) is impracticable: You have 
to run CMake for dune-common, build dune-common with VS, run 
CMake for dune-geometry, build dune-geometry with VS and so 
forth
- CTests creates no targets in VS, thus tests cannot be built 
or run
- There are several Unix-specific code parts. With Cygwin and 
MinGW they provide these headers but on pure Windows they do 
not exist.
- Microsoft's C++ compiler struggles with some C++ constructs 
we use:
   + it dislikes and, or, not instead of &&, ||, !
   + long literals for variable assignments with more then 64 
(?) digits.
   + the template meta-programs in dune-grid and 
dune-localfunctions fail to compile

== Glory Details ==
I spend one and a half days using Dune with Windows. Most of 
the time took updating Windows with hundreds of updates and 
dozens of restarts. Installing Visual Studio, a Git client and 
CMake is less comfortable as I am used to, but it was done 
quickly.
I had to disable the Fortran-enable hack. Right after that, 
configure went through. Make obviously did not work, so I had 
to open the build-directory with VS and could see several of 
dune-common's build targets.
After some crude hacks I was able to build dune-common. The 
attached patch contains all my changes to dune-common. They 
are not meant to be productive code but to get the code 
passing the compiler.
Next I had to call CMake for dune-geometry, adding 
dune-common's build directory as an argument. The list of 
arguments will grow with every module dependency and will get 
impracticable for e.g. PDELab. Building dune-geometry was 
possible after another round of quick hacks, cf. the other 
attached patch.
Dune-grid and dune-localfunctions could not be compiled due to 
some template meta-programing issue. Dune-istl does not build 
a library, so there was nothing left to compile. I was not 
able to run any of our test programs, as there were no 
auto-generated build-targets for these and CTest wanted to 
call make which did again not work. Maybe one could manually 
add such a target, I did not try.

== lessens learned ==
- With CMake Windows support for Dune seems to be realistic 
for the first time. Sure, there will be plenty to do but 
technically it could be done.
- Microsoft's Visual Studio C++ 2013 compiler is better then I 
thought. I hope with the next version  it becomes even better. 
I was not able to use the latest developer snapshot, as you 
have to have an MSDN account or something similar.
- Intel's compiler license is very prohibitive in Windows 
land. Another strong argument for open source. Maybe LLVM will 
advance and can be included into VS .
- Our approach to create a CMake project per dune-module might 
be a bad choice. For application modules that generates a 
stack of ten or even more modules. Currently, I have no idea 
how to do better, but a kind of meta-project would be helpful 
and could save time during configure. But that's out of scope 
as long as we stay compatible to autotools.
- I think with an Intel compiler (and an appropriate license) 
a willing and skilled C++ programmer can port Dune to Windows. 
Maybe we have to change the way we organize our tests. 
Probably we have to figure out how to configure and build the 
modules in a less manual and painful way.

Bye
Christoph
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