Cannot build shared libraries using CMake with MSVC and Intel Fortran compiler

[Baljak]

Bug description
When setting CMake flag BUILD_SHARED_LIBS to ON, OpenFAST can't be built with MSVC and Intel Fortran compiler. Tested with MSVC 2015 and 2019 and ifort 18.0 and 19.0. The reason comes from the fact that DLLEXPORT is not defined for functions which need to be exported, so ifort is unable to produce .lib import libraries.

To Reproduce
Steps to reproduce the behavior:

1. Compile with MSVC and Intel Fortran compiler, no matter the version
2. See the link error, for example nwtclibs.lib not found even if nwtclibs.dll was compiled correctly.

Expected behavior
It should be possible to compile all libraries as DLLs using MSVC and Intel Fortran.

OpenFAST Version
2.2.0

**************************************************************************************************
 OpenFAST

 Copyright (C)  National Renewable Energy Laboratory
 Copyright (C)  Envision Energy USA LTD

 This program is licensed under Apache License Version 2.0 and comes with ABSOLUTELY NO WARRANTY.
 See the "LICENSE" file distributed with this software for details.
 **************************************************************************************************

 OpenFAST-v2.0.0
 Compile Info:
  - Architecture: 64 bit
  - Precision: double
  - Date: Nov 27 2018
  - Time: 17:19:38
 Execution Info:
  - Date: 11/29/2018
  - Time: 10:52:28-0700

System Information (please complete the following information):

• OS: Windows 10 64
• Compiler: MSVC 2019 and Intel Fortran Compiler 19.0
• Compiler settings: BUILD_SHARED_LIBS set to ON

[bjonkman]

On Windows (regardless of compiler), you need to explicitly state which routines can be called from within a DLL. None of the modules except MAP++ have been set up that way, so either the BUILD_SHARED_LIBS option should be removed or all of the modules need to have their source code modified to work this way. Personally, I would just remove that as a build option on Windows.

[rafmudaf]

I agree, @bjonkman, I'll check for that in CMake.

[Baljak]

On Windows (regardless of compiler), you need to explicitly state which routines can be called from within a DLL.

Not exactly, this is only required with MSVC (and ifort on Windows since it relies on MSVC linker) to generate import librairies. MinGW does not require export definitions and as such works perfectly fine with the BUILD_SHARED_LIBS option.

I agree though that adding DLLEXPORT definitions to all functions which need to be exported would be quite long so it may be better to disable the option for MSVC.