Linux: <sys/sysctl.h> missing

[darealshinji]

When I try to compile on Linux with GCC I get this error:

  CC       xo_syslog.lo
xo_syslog.c:61:10: fatal error: sys/sysctl.h: No such file or directory
   61 | #include <sys/sysctl.h>
      |          ^~~~~~~~~~~~~~

The only sysctl.h file I have on my system is linux/sysctl.h:

 $ find /usr/include/* -name 'sysctl.h'
/usr/include/linux/sysctl.h

Simply commenting out the line however helps too.
Maybe add a check for this header file to configure.ac?
On Ubuntu the path sys/sysctl.h seems to be only available in the dietlibc package.

[AnttiNykanen]

Ran into this as well on Fedora 37.

glibc 2.32 removes sys/sysctl.h. From https://lwn.net/Articles/828210/ :

The deprecated <sys/sysctl.h> header and the sysctl function have been
removed. To support old binaries, the sysctl function continues to
exist as a compatibility symbol (on those architectures which had it),
but always fails with ENOSYS. This reflects the removal of the system
call from all architectures, starting with Linux 5.5.

Since it compiles fine by removing the header from xo_syslog.c , probably that's the correct way to deal with the issue?

[darealshinji]

Better put some #ifdef check around it for systems that absolutely need it (FreeBSD?) and keep it disabled by default otherwise.