I tried that. If you make it `Cint`, then you need to say `ccall(:jl_is_debugbuild, Bool, ()) == 1`, and the problem I ran into is that it seems that `==` isn't yet defined at this stage of the boot process. Declaring the return type as `Bool` fixed this. This was easier than what I started to do, changing the return type to `jl_value_t*`.

FYI in `util.jl` there's also a `ccall` to `jl_is_debugbuild` that declares the return type as `Bool`, which is where I got the idea from.