Add constexpr and boost::variant workarounds for vs2015. #772
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vissarion
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Nov 13, 2020
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I do not have a strong opinion against supporting VS2015, so I am ok with this patch.
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| // Workaround for VS2015 | ||
| #if (_MSC_VER < 1910) |
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should it be explicitly _MSC_VER == 1900 or there is hope that the workaround will also work with older than VS15 versions ?
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No, I don't think that the older VS will compile the library.
This way the checks are symmetric, i.e. < 1910 vs >= 1910.
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@mloskot @barendgehrels Do you have anything against merging it? |
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The #ifdefs were disabling |
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Yes, better, thanks. |
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If you see our regression tests it looks like the majority of them compiles with VS2015:
https://www.boost.org/development/tests/develop/developer/geometry.html
Therefore I checked how much effort would it take to make all of them to compile. It seems that it was not much. VS2015 doesn't have full
constexprsupport andboost::variant's is implemented using dummy template parameters instead of parameter pack.For
constexprit was sufficient to disable it in some places and add explicitly initialize class member in other.In order to analyze types of
boost::variantI decided to not use Boost.MPL as it was before but instead to check raw template parameters, i.e. to check if they are geometries or not. This works for both dummy parameters and types that are not geometries. And while currently non-geometries are not supported in other places of the library we could consider supporting them. An example would be something like:Right now this code would not compile. At least I think it would not. But I don't see a semantic reason why it shouldn't. So in the future we could consider expanding the change done in this PR to the whole library.
What do you think about these workarounds?
Does it make sense to support vs2015?