only_if_constant  148 thread.c       #define only_if_constant(expr, notconst) __builtin_choose_expr(__builtin_constant_p(expr), (expr), (notconst))
only_if_constant  150 thread.c       #define only_if_constant(expr, notconst) (__builtin_constant_p(expr) ? (expr) : (notconst))
only_if_constant  153 thread.c       #define only_if_constant(expr, notconst) notconst