REG_ESUBREG_IDX   155 maint/gnulib/lib/regcomp.c #define REG_EBRACK_IDX	(REG_ESUBREG_IDX + sizeof "Invalid back reference")
REG_ESUBREG_IDX   194 maint/gnulib/lib/regcomp.c     REG_ESUBREG_IDX,