[SOLVED] Py ILM Base not compiling on windows

Py ILM Base not compiling on windows

I've downloaded the latest copy from Latest Open EXR repo and compiled most everything without any problems. However, when I get to PyILMBase it fails.

There are two distinct issues with my attempts:

Error C2491 'PyImath::FixedArray::name': definition of dllimport function not allowed PyImath (...)\src\pyilmbase-2.2.1\PyImath\PyImath.cpp 41

and an import to unistd.h that kind of gets addressed Here

my question being, has anybody successfully compiled this for windows? It seems odd that I can't find any specific info about that compiling error. Am I missing something in the way that C++ works?

This project makes extensive use of whatever it is that causes the error C2491, so going in and changing it would be a little complicated

Solution

IlmBase is compiled as a shared library. A shared library must provide their function declarations in order your program can find them. It's perform by declaring them as dllimport or dllexport depending on the situation.

__declspec(dllimport): imports the implementation from a DLL so your application can use it.
__declspec(dllexport): tells the linker that you want this object to be made available for other DLL's to import. It is used when creating a DLL that others can link to.

These keywords are generally handled by a single macro. In your case PYIMATH_EXPORT.

These lines are from PyImathTask.h

#if defined(PYIMATH_EXPORTS)                         // create library  
  #define PYIMATH_EXPORT __declspec(dllexport)  
#else                                                // use library  
  #define PYIMATH_EXPORT __declspec(dllimport)  
#endif

So, because you want to make these functions available from your application, you must add PYIMATH_EXPORTS as a preprocessor definition.

Actually, PyIMath's properties mispells it - they've write it as PyImath_EXPORTS - ... To fix that, in vs2015, go to the PyImath's properties > Configuration Properties > C/C++ > Preprocessor > Replace PyImath_EXPORTS by PYIMATH_EXPORTS.

It's probably the same thing for PyIex...