# Unresonable checks of Linux headers, while running CMake on FreeBSD 13
**URL:** https://discourse.cmake.org/t/unresonable-checks-of-linux-headers-while-running-cmake-on-freebsd-13/2539
**Category:** Usage
**Created:** [January 13, 2021, 10:10pm UTC](https://discourse.cmake.org/t/unresonable-checks-of-linux-headers-while-running-cmake-on-freebsd-13/2539 "2021-01-13T22:10:55Z")
**Posts on this page:** 4
**Page:** 1
### Author:  [@Ivan\_Serdyuk](https://discourse.cmake.org/u/Ivan_Serdyuk)
#### Post date: [January 13, 2021, 10:10pm UTC](https://discourse.cmake.org/t/unresonable-checks-of-linux-headers-while-running-cmake-on-freebsd-13/2539/1 "2021-01-13T22:10:56Z")
Hello.
I am experiencing some inappropriate behavior of CMake (apparently cause of both lack of platform specific patch and due to a need to re-write project specific build rules).
Some headers have no sense on BSD systems. The current issue is more about specifically kqueue versus epoll headers.
I wasn’t to reference Github’s issue directly - but an opened one has an ID 42282.
So while building gollvm (FreeBSD 13.0, x86\_64) I got this:
> CMake Error at **tools/gollvm/cmake/modules/AutoGenGo.cmake:389** (message):
> \*\*\* struct epoll\_event data.fd offset unknown
> Call Stack (most recent call first):
> **tools/gollvm/libgo/CMakeLists.txt:323** (mkepoll)
> This shouldn’t be even considered, since epoll is present on Linux (but not on FreeBSD).
> Instead it has check for kqueue.
> The above Github issue contains the list of libgo’s source files, some which depend on kqueue.
> Despite the fact that gollvm project has CMake’s configuration as a replacement of “configure” and autotools - ensuring that libgo’s C files would compiled, by probing via some dummy, should be enough.
> I wouldn’t expect anything expect an abort, if the probed sample source file wouldn’t compile.
---
### Author:  [@bill.hoffman](https://discourse.cmake.org/u/bill.hoffman)
#### Post date: [January 13, 2021, 10:40pm UTC](https://discourse.cmake.org/t/unresonable-checks-of-linux-headers-while-running-cmake-on-freebsd-13/2539/2 "2021-01-13T22:40:54Z")
These are the issues you are referring to:
>
>
> Hi.
> I was investigating current blocking issues, on FreeBSD 13.0.
> $cmake -DCMAKE\_CXX\_FLAGS=' -I~/workarea/freebsd\_src/include ' -DCMAKE\_C\_FLAGS=' -I~/workarea/freebsd\_src/include ' ../
>
> \-- The C compiler identification is...
> **[gollvm - Git at Google](https://go.googlesource.com/gollvm/)**
This looks like a libgo CMakeLists.txt issue and not an issue with CMake itself AFAIK.
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### Author:  [@Ivan\_Serdyuk](https://discourse.cmake.org/u/Ivan_Serdyuk)
#### Post date: [March 22, 2021, 8:29pm UTC](https://discourse.cmake.org/t/unresonable-checks-of-linux-headers-while-running-cmake-on-freebsd-13/2539/3 "2021-03-22T20:29:22Z")
I see that this script is working, on FreeBSD 12.0 Aarch64:
[https://github.com/skroll/cmake-modules/blob/master/modules/CheckKqueue.cmake](https://github.com/skroll/cmake-modules/blob/master/modules/CheckKqueue.cmake)
> $ git clone [GitHub - skroll/cmake-modules: A collection of CMake modules to simplify projects.](https://github.com/skroll/cmake-modules)
> Cloning into ‘cmake-modules’…
> remote: Enumerating objects: 24, done.
> remote: Counting objects: 100% (24/24), done.
> remote: Compressing objects: 100% (15/15), done.
> remote: Total 24 (delta 9), reused 24 (delta 9), pack-reused 0
> Receiving objects: 100% (24/24), done.
> Resolving deltas: 100% (9/9), done.
> $ cd cmake-modules
> $ ls
> CMakeLists.txt README.md modules
> $ mkdir build
> $ cd build
> $ cmake …
> – The C compiler identification is Clang 8.0.1
> – The CXX compiler identification is Clang 8.0.1
> – Detecting C compiler ABI info
> – Detecting C compiler ABI info - done
> – Check for working C compiler: /usr/bin/cc - skipped
> – Detecting C compile features
> – Detecting C compile features - done
> – Detecting CXX compiler ABI info
> – Detecting CXX compiler ABI info - done
> – Check for working CXX compiler: /usr/bin/c++ - skipped
> – Detecting CXX compile features
> – Detecting CXX compile features - done
> CMake Deprecation Warning at CMakeLists.txt:2 (cmake\_minimum\_required):
> Compatibility with CMake \< 2.8.12 will be removed from a future version of
> CMake.
>
> Update the VERSION argument value or use a … suffix to tell
> CMake that the project does not need compatibility with older versions.
>
> – Check if the system supports kqueue
> – Looking for kqueue
> – Looking for kqueue - found
> – Check if the system supports kqueue - yes
> – Check if the system supports epoll
> – Looking for epoll\_create
> – Looking for epoll\_create - not found
> – Check if the system supports epoll - no
> – Configuring done
> – Generating done
> – Build files have been written to: /usr/home/oceanfish81/cmake-modules/build
> $ uname -a
> FreeBSD ams1-c1-large-arm-01 12.1-RELEASE FreeBSD 12.1-RELEASE r354233 GENERIC arm64
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### Author:  [@fenrir](https://discourse.cmake.org/u/fenrir)
#### Post date: [March 23, 2021, 6:54am UTC](https://discourse.cmake.org/t/unresonable-checks-of-linux-headers-while-running-cmake-on-freebsd-13/2539/4 "2021-03-23T06:54:01Z")
I don’t see checking any headers in that log.
But if you’re referring to the “epoll” - it’s not CMake itself - it’s the project that decides to check for it. From the other hand this is the role of this system - to check for stuff and setup build accordingly.