fatal error: sys/cdefs.h: No such file or directory|

Solution 1:

If you are on an amd64 installation, you can try to install the package libc6-dev-i386. This helped me solve the same issue you encountered while trying to compile smm from i8kutils.

Solution 2:

On my machine, where I've probably screwed around too much with 32 and 64 bit architecture files, I resolved this issue by installing g++-multilib.

Solution 3:

Typing the command:

sudo apt-get --reinstall install libc6 libc6-dev

solved the problem.