How to create a DLL with SWIG from Visual Studio 2010

Question

I've been trying for weeks to get Microsoft Visual Studio 2010 to create a DLL for me with SWIG. If you have already gone through this process, would you be so kind as to give a thoughtful step-by-step process explanation? I've looked everywhere online and have spent many many hours trying to do this; but all of the tutorials that I have found are outdated or badly explained.

I have succeeded in going through this process with cygwin; but as some of you know, a cygwin DLL is not very practical.

As a result, I have .i, .cpp, and .h files that I know can create a DLL together. I just need to know how to do this with Visual Studio C++ 2010. The language that I am targeting is Python.

Solution

Step-by-step instructions. This assumes you have the source and are building a single DLL extension that links the source directly into it. I didn't go back through it after creating a working project, so I may have missed something. Comment on this post if you get stuck on a step. If you have an existing DLL and want to create a Python extension DLL that wraps it, this steps are slightly different. If you need help with that comment on this post and I will extend it.

Edit 8/19/2012: If starting with a C example, don't use -c++ in step 13 and use .c instead of .cxx for the wrap file extension in steps 14 and 19.

1. Start Visual Studio 2010
2. File, New, Project from Existing Code...
3. Select "Visual C++" project type and click Next.
4. Enter project file location where the .cpp/.h/.i files are.
5. For Project Name, choose the name used in %module statement in your .i file (case matters).
6. Select project type "Dynamically linked library (DLL) project" and click Next.
7. Add to Include search paths the path to the Python.h file, usually something like "C:\Python27\include" and click Next.
8. Click Finish.
9. Right-click the Project in Solution Explorer, Add, Existing Item..., and select your .i file.
10. Right-click the .i file, Properties, and select Configuration "All Configurations".
11. Change Item Type to "Custom Build Tool" and click Apply.
12. Select "Custom Build Tool" in Properties (it will appear after Apply above).
13. Enter Command Line of "swig -c++ -python -outdir $(Outdir) %(Identity)" (this assumes SWIG is in your path and redirects the generated .py file to the Debug or Release directory as needed).
14. In Outputs enter "%(Filename)_wrap.cxx;$(Outdir)%(Filename).py".
15. Click OK.
16. Right-click the .i file, and select Compile.
17. Right-click the project, Add, New Filter, name it "Generated Files".
18. Right-click "Generated Files", click Properties, and set "SCC Files" to "False" (if you use source-control, this prevents VS2010 trying to check in the generated files in this filter).
19. Right-click "Generated Files", Add, Exiting Item and select the _wrap.cxx file that was generated by the compile.
20. Right-click the project, Properties.
21. Select Configuration "All Configurations".
22. Select Configuration Properties, Linker, General, Additional Library Directories and add the path to the python libraries, typically "C:\Python27\libs".
23. Select Configuration Properties, General and set TargetName to "_$(ProjectName)".
24. Set Target Extension to ".pyd".
25. Build the "Release" version of the project. You can't build the Debug version unless you build a debug version of Python itself.
26. Open a console, go to the Release directory of the project, run python, import your module, and call a function!

Comments

[user1449530]

Thank you Mark for saving me (and probably a lot of other people) the trouble of finding this process through trial and error! I had to add to "Project Properties >> VC++ Directories >> Include Directories" my C:\Python27\include; but otherwise it worked like a dream! By the way, I was using Microsoft Visual C++ Express; but the process is obviously the same.

[Shmil The Cat]

@Mark - great post, can you kindly extend it to the case one has an exiting DLL ?

[odedfos]

It is worth noting SWIG will not work with python 64 bit version. Use the 32 bit version instead.

[Mark Tolonen]

@odedfos Not true. It works fine with 64-bit. That's the main way I use it. Any DLLs being wrapped have to be 64-bit as well.

[Jiminion]

Great answer. Thank you very much. Just an FYI, don't actually write the quotes when entering, say: "swig -c++ -python -outdir $(Outdir) %(Identity)"

[delrocco]

If your Python install is 32-bit, then you must use configuration 32-bit. And so forth with 64-bit. You can't cross them or you will get unresolved externals.

[delrocco]

For Visual Studio 2017 there is no right-click "Compile" option for .i files. Note that you don't have to do any custom compiling of .i files from Visual Studio. You can just call swig from a shell first, then add the generated _wrap.c/.cpp to your Visual Studio project manually.