Preprocessor macro expanding to a type attribute
#include <SYS/TYPES.H>
int __CONST_ATTR__ function(args...);
This macro expands to a compiler-specific attribute telling that the function return value depends only on its arguments. It may not depend on global variables or content of dereferenced pointers.
It enables the compiler to do better optimizations.
When using the gcc compiler, this macro expands to __attribute__((__const__))
.