The man page indicates that CPU_AND() and CPU_ASSIGN() take a variable, not a const on the source, even though it doesn't make much sense. But with older libcs, this triggers a build warning: src/cpuset.c: In function 'ha_cpuset_and': src/cpuset.c:53: warning: initialization discards qualifiers from pointer target type src/cpuset.c: In function 'ha_cpuset_assign': src/cpuset.c:101: warning: initialization discards qualifiers from pointer target type Better stick stricter to the documented API as this is really harmless here. There's no need to backport it (unless build issues are reported, which is quite unlikely).