# Can the CuArray/CuPtr in CUDA.jl be directly passed to foreign functions?
**URL:** https://discourse.julialang.org/t/can-the-cuarray-cuptr-in-cuda-jl-be-directly-passed-to-foreign-functions/46939
**Category:** GPU
**Tags:** question
**Created:** [September 19, 2020, 9:58pm UTC](https://discourse.julialang.org/t/can-the-cuarray-cuptr-in-cuda-jl-be-directly-passed-to-foreign-functions/46939 "2020-09-19T21:58:13Z")
**Posts on this page:** 3
**Page:** 1
### Author:  [@weylspinor](https://discourse.julialang.org/u/weylspinor)
#### Post date: [September 19, 2020, 9:58pm UTC](https://discourse.julialang.org/t/can-the-cuarray-cuptr-in-cuda-jl-be-directly-passed-to-foreign-functions/46939/1 "2020-09-19T21:58:13Z")
Hi,
I am just wondering if there is any way to directly pass `CuArrays` or `CuPtr` in `CUDA.jl` to C/C++, like passing `Core.Array` or `Core.Ref`. For example, I would like to define a C function which gets a device memory pointer (with type `double*`, `cuComplex*`, etc.) and pass `CuArrays` or `CuPtr` to it.
I am asking this question because I want to minimize the data transfer between a device and a host. Of course I can pass `CuArrays` or `CuPtr` to C functions by first transferring them to a host but if the size of `CuArrays` becomes large, this will produce big overhead…
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### Author:  [@maleadt](https://discourse.julialang.org/u/maleadt)
#### Post date: [September 21, 2020, 6:16am UTC](https://discourse.julialang.org/t/can-the-cuarray-cuptr-in-cuda-jl-be-directly-passed-to-foreign-functions/46939/2 "2020-09-21T06:16:01Z")
Yes, you can pass a `CuPtr`. Just specify `CuPtr` in your `ccall` signature and pass a `CuArray`, automatic conversion will do the rest. Of course, you’ll need to make sure the array stays alive on the Julia side for as long as the C code can use the pointer, but that’s not GPU specific.
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### Author:  [@Ellipse0934](https://discourse.julialang.org/u/Ellipse0934)
#### Post date: [September 22, 2020, 11:44am UTC](https://discourse.julialang.org/t/can-the-cuarray-cuptr-in-cuda-jl-be-directly-passed-to-foreign-functions/46939/3 "2020-09-22T11:44:10Z")
Since it’s likely that your C/C++ program is a different process you’ll have to use the CUDA IPC API. [https://github.com/NVIDIA/cuda-samples/tree/master/Samples/simpleIPC](https://github.com/NVIDIA/cuda-samples/tree/master/Samples/simpleIPC)