Thanks, that worked! I should have figured that myself, I was so busy trying to get rid of UncheckedArray in other bits of code that c2nim had created that I didnt realize it might be usefull here.
For future nim forum users needing a solution: c2nim was converting float **data; Run to data*: ptr ptr cfloat Run After the c2nim conversion I run a postprocessing script that replaces that line with: data*: ptr UncheckedArray[UncheckedArray[cfloat]] Run