Fix windows build by exporting public static const class variables

[Levi-Armstrong]

No description provided.

[Levi-Armstrong]

@johnwason I believe this should fix the windows build issue in your open MR.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 84.81%. Comparing base (18c0b5e) to head (c0b35a8).

Additional details and impacted files

@@           Coverage Diff           @@
##           master     #491   +/-   ##
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  Coverage   84.81%   84.81%           
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  Files         231      231           
  Lines       15737    15737           
=======================================
  Hits        13347    13347           
  Misses       2390     2390           

see 1 file with indirect coverage changes

[johnwason]

The export is applied to the class, and each individual library needs their own export macro.

Here is an example of an export macro on a class:

https://github.com/robotraconteur/robotraconteur/blob/b0c1ccab189b059f3b59874a303a6a6f52e321d7/RobotRaconteurCore/include/RobotRaconteur/DataTypes.h#L250

I can take a look this week.

[Levi-Armstrong]

I thought everything would get exported when using cmake WINDOWS_EXPORT_ALL_SYMBOLS and only these need to be exported manually.

[johnwason]

The module definition file will be passed to the linker causing all symbols to be exported from the .dll. For global data symbols, __declspec(dllimport) must still be used when compiling against the code in the .dll. All other function symbols will be automatically exported and imported by callers.

https://cmake.org/cmake/help/latest/prop_tgt/WINDOWS_EXPORT_ALL_SYMBOLS.html

Data symbols still need to be exported. For classes with static fields I think the entire class needs to be exported but I haven't used this before.