Does this actually work on MSVC?

[cbeck88]

Hi, I started adding appveyor testing to my lib that was using this, and I found that msvc wouldn't work with it. I thought that I had gotten it to work when I pasted into the online compiler... but now I'm not sure of that.

I googled around and found an SO question about __VA_ARGS__ on MSVC apparently being buggy:

http://stackoverflow.com/questions/5134523/msvc-doesnt-expand-va-args-correctly
http://stackoverflow.com/questions/32399191/va-args-expansion-using-msvc
http://stackoverflow.com/questions/21869917/visual-studio-va-args-issue

Do you know if map macro takes this into account?

Would you potentially be interested in a patch that implements one of these workarounds if not?

I'm not really a windows person... and I'm kind of hoping that MSVC will be abandoned en masse when clang is supported in visual studio. But this shouldn't actually be that hard to fix I think...

(It may very well actually be a bug in my code unrelated to map macro, I'm not totally sure.)

[swansontec]

I don't have a Windows box at the moment, but if you provide a pull request, I would be happy to merge it. I think the approach in visit_struct looks reasonable. One could arguably use the VS2015 solution on all platforms, avoiding the ugly #ifdef, since it's simple enough.

[cbeck88]

That commit didn't actually work unfortunately, I don't have a windows box either to test it right now. I plan to come back to this some time soon, or maybe over the holidays.

[9chu]

Seems not work under MSVC (VS2017)

[akbyrd]

It works with /Zc:preprocessor which was added in VS 2019 / 16.5 (and a little earlier as /experimental:preprocessor).