# Cannot compile Slicer on Mac - macOS Sierra + clang 9 + cmake 3.9.1

**URL:** <https://discourse.slicer.org/t/cannot-compile-slicer-on-mac-macos-sierra-clang-9-cmake-3-9-1/1104>\
**Category:** Development\
**Tags:** build\
**Created:** [September 22, 2017, 6:27pm UTC](https://discourse.slicer.org/t/cannot-compile-slicer-on-mac-macos-sierra-clang-9-cmake-3-9-1/1104 "2017-09-22T18:27:59Z")\
**Posts on this page:** 1\
**Showing post:** 5

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**Author:** ![fedorov](https://sea2.discourse-cdn.com/flex002/user_avatar/discourse.slicer.org/fedorov/32/14_2.png) [@fedorov](https://discourse.slicer.org/u/fedorov)\
**Post date:** [September 22, 2017, 7:29pm UTC](https://discourse.slicer.org/t/cannot-compile-slicer-on-mac-macos-sierra-clang-9-cmake-3-9-1/1104/5 "2017-09-22T19:29:59Z")

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> [@jcfr](#):
>
> we now explicitly pass CMAKE\_CXX\_STANDARD

I confirm it is set to 98 in SimpleITK cache:

```plaintext
$ grep -r CXX_STANDARD CMakeCache.txt
CMakeCache.txt:CMAKE_CXX_STANDARD:STRING=98
CMakeCache.txt:CMAKE_CXX_STANDARD_REQUIRED:BOOL=ON

```

But as @blowekamp said, C++11 is required.

Considering your comment in the above referenced thread ([Transition to VTK 8.0 - #4 by jcfr](https://discourse.slicer.org/t/transition-to-vtk-8-0/379/4)), I guess I am being forced to switch to VTKv8 😉 I will try that next.

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