In Julia generally missing is favored over NaN, among other because NaN work only for floating point types, and because the origin of NaNs can be hard to trace once they have infected the data.
However, IEEE745 has also signaling NaNs, supported in C++11, but not in Julia at least not “officially”. I found this discussion where also a solution for Linux/x86 is outlined. A problem seems to be that LLVM (still?) does not support hardware exceptions? Is there any updated “insider” information which I have not been able to find? A package for at least Linux/x86?
Having worked with various hardware that signals when something is wrong I presume that the signaling NaNs would be a good and efficient solution in many cases when computations are within floating points.