# Segmentation fault when using ccall to call a BLAS-like extension function from Intel MKL

**URL:** https://discourse.julialang.org/t/segmentation-fault-when-using-ccall-to-call-a-blas-like-extension-function-from-intel-mkl/123377
**Category:** General Usage
**Tags:** ccall, mkl, segfault
**Created:** [December 3, 2024, 1:22am UTC](https://discourse.julialang.org/t/segmentation-fault-when-using-ccall-to-call-a-blas-like-extension-function-from-intel-mkl/123377 "2024-12-03T01:22:12Z")
**Posts on this page:** 1
**Showing post:** 4

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### Author: ![giordano](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/giordano/32/2166_2.png) [@giordano](https://discourse.julialang.org/u/giordano)
#### Post date: [December 3, 2024, 2:33am UTC](https://discourse.julialang.org/t/segmentation-fault-when-using-ccall-to-call-a-blas-like-extension-function-from-intel-mkl/123377/4 "2024-12-03T02:33:00Z")

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> [@NatSpring](#):
>
> ```julia
> $ nm -D /opt/intel/oneapi/mkl/latest/lib/libmkl_rt.so | grep mkl_dimatcopy
> 00000000005ff510 T mkl_dimatcopy
> 00000000005ff510 T mkl_dimatcopy_
> 00000000005ff640 T mkl_dimatcopy_batch
> 00000000005ff640 T mkl_dimatcopy_batch_
> 00000000005ff770 T mkl_dimatcopy_batch_strided
> 00000000005ff770 T mkl_dimatcopy_batch_strided_
> 
> ```

In hindsight, the fact that both the C and the Fortran symbols point to the same address should have been a giveaway that all arguments must be pointers (only way that’d work in Fortran), despite what’s written in the documentation.

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_[View the full topic](https://discourse.julialang.org/t/segmentation-fault-when-using-ccall-to-call-a-blas-like-extension-function-from-intel-mkl/123377)._