/usr/include/clc/math/fmod.h is in libclc-dev 0.2.0+git20180312-1.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
1 2
#define __CLC_BODY <clc/math/fmod.inc> #include <clc/math/gentype.inc>