# Pointer (Julia) not modified after ccall to C function which uses another C function

**URL:** <https://discourse.julialang.org/t/pointer-julia-not-modified-after-ccall-to-c-function-which-uses-another-c-function/10455>\
**Category:** General Usage\
**Tags:** ccall\
**Created:** [April 20, 2018, 1:13pm UTC](https://discourse.julialang.org/t/pointer-julia-not-modified-after-ccall-to-c-function-which-uses-another-c-function/10455 "2018-04-20T13:13:46Z")\
**Posts on this page:** 1\
**Showing post:** 15

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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:** [April 20, 2018, 6:17pm UTC](https://discourse.julialang.org/t/pointer-julia-not-modified-after-ccall-to-c-function-which-uses-another-c-function/10455/15 "2018-04-20T18:17:24Z")

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The exact code depends on how are the lifetime managed (e.g. whether the struct need to stay alive for a long time). For the general idea, see [How to keep a reference for C structure to avoid GC? - #4 by tk3369](https://discourse.julialang.org/t/how-to-keep-a-reference-for-c-structure-to-avoid-gc/9310/4), including all the context.

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