WARNING: convert(::Type{Ptr}, ::CUDArt.CudaPtr{Float32}) methods should be converted to be methods of unsafe_convert

[denizyuret]

The latest snapshot of Julia makes CUDArt unusable because of nonstop warnings of the type given above. The warnings are generated by ccall instructions, and I suspect something needs to be fixed with ccall?

[denizyuret]

Part of the issue seems to be that I can't seem to turn warnings off on worker processes. Even if I start julia with --depwarn=no, the workers do not inherit this. Maybe inheriting JLOptions() by children should be another issue?

[JeffBezanson]

This recent change deprecates conversion to Ptr since it's considered dangerous. The warning is telling all libraries that define conversions to Ptr to define unsafe_convert instead.

@vtjnash The following might be a problem, since it refers to a definition in Base:

julia> ccall(:jl_value_ptr, Ptr{Void}, (Ptr{Void},), 1)
WARNING: convert(::Type{Ptr}, ::Int64) methods should be converted to be methods of unsafe_convert
 in depwarn at ./deprecated.jl:40
 in anonymous at no file
Ptr{Void} @0x0000000000000001

[vtjnash]

i might want to improve the text of that message, but that conversion is an error in C too.

we should probably add eval(Base, :(const unsafe_convert = cconvert)) to Compat.jl for v0.3

[JeffBezanson]

I think it might be more user-friendly for the fallbacks to be

cconvert(T::Type, x) = x
unsafe_convert(T::Type, x) = convert(T, x)

Those are easier to reason about. Then you have the option of just defining methods for convert, and they will be used, but if you want more safety you can choose to define Ptr conversions only for unsafe_convert.

(EDIT: This was Jameson's original approach in #9986, and he later changed it.)