DBG_EXTRAS
#define DBG_U0 (1LL << DBG_EXTRAS(0)) /* 0 - ad-hoc extra flags */
#define DBG_U1 (1LL << DBG_EXTRAS(1)) /* 1 - for short term */
#define DBG_U2 (1LL << DBG_EXTRAS(2)) /* 2 - extra tracing */
#define DBG_U3 (1LL << DBG_EXTRAS(3)) /* 3 - when needed */
#define DBG_LINE (1LL << DBG_EXTRAS(7)) /* @ ($LINENO) */
#define DBG_PID (1LL << DBG_EXTRAS(8)) /* $ ($$) */
#define DBG_NEST (1LL << DBG_EXTRAS(9)) /* ^ */