/usr/include/atlas/atlas_ssyrNX.h is in libatlas-dev 3.10.1-4.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
1 2 3 4
#ifndef ATLAS_SSYR_H #define ATLAS_SSYR_H #define ATL_S1NX 0 #endif