# Ptr{Ptr{Cint}}

**URL:** https://discourse.julialang.org/t/ptr-ptr-cint/10883
**Category:** General Usage
**Created:** [May 14, 2018, 10:20am UTC](https://discourse.julialang.org/t/ptr-ptr-cint/10883 "2018-05-14T10:20:17Z")
**Posts on this page:** 5
**Page:** 1

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### Author: ![tobias.knopp](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/tobias.knopp/32/7551_2.png) [@tobias.knopp](https://discourse.julialang.org/u/tobias.knopp)
#### Post date: [May 14, 2018, 10:20am UTC](https://discourse.julialang.org/t/ptr-ptr-cint/10883/1 "2018-05-14T10:20:18Z")

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Hi,

does someone know how to replace `Ptr{Ptr{Cint}}` by a `Ref` based solution?

Example code is:

[https://github.com/JuliaIO/HDF5.jl/blob/88a80661357844ccf0bc0e6a46e419e7bf8a68e5/src/HDF5.jl#L1602](https://github.com/JuliaIO/HDF5.jl/blob/88a80661357844ccf0bc0e6a46e419e7bf8a68e5/src/HDF5.jl#L1602)

Definition of C function is here:

[https://github.com/JuliaIO/HDF5.jl/blob/88a80661357844ccf0bc0e6a46e419e7bf8a68e5/src/HDF5.jl#L2083](https://github.com/JuliaIO/HDF5.jl/blob/88a80661357844ccf0bc0e6a46e419e7bf8a68e5/src/HDF5.jl#L2083)

Thanks,

Tobi

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<div class="post-metadata">

### Author: ![yuyichao](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/yuyichao/32/20_2.png) [@yuyichao](https://discourse.julialang.org/u/yuyichao)
#### Post date: [May 14, 2018, 11:02am UTC](https://discourse.julialang.org/t/ptr-ptr-cint/10883/2 "2018-05-14T11:02:52Z")

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The code looks correct as is. You can replace the array by a Ref of the same eltype for performance.

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### Author: ![tobias.knopp](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/tobias.knopp/32/7551_2.png) [@tobias.knopp](https://discourse.julialang.org/u/tobias.knopp)
#### Post date: [May 14, 2018, 11:57am UTC](https://discourse.julialang.org/t/ptr-ptr-cint/10883/3 "2018-05-14T11:57:04Z")

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Hm ok. The actual issue is that `mmap` is not working on Windows. and I thought that this might be the root cause.

([https://github.com/JuliaIO/HDF5.jl/issues/89](https://github.com/JuliaIO/HDF5.jl/issues/89))

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### Author: ![yuyichao](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/yuyichao/32/20_2.png) [@yuyichao](https://discourse.julialang.org/u/yuyichao)
#### Post date: [May 14, 2018, 12:37pm UTC](https://discourse.julialang.org/t/ptr-ptr-cint/10883/4 "2018-05-14T12:37:16Z")

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If anything, incorrect use of `Ptr`/`Ref` is rarely platform dependent.

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<div class="post-metadata">

### Author: ![tobias.knopp](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/tobias.knopp/32/7551_2.png) [@tobias.knopp](https://discourse.julialang.org/u/tobias.knopp)
#### Post date: [May 14, 2018, 1:10pm UTC](https://discourse.julialang.org/t/ptr-ptr-cint/10883/5 "2018-05-14T13:10:16Z")

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ok thanks. Then its beyond what I can investigate.