https://gcc.gnu.org/bugzilla/show_bug.cgi?id=78839
--- Comment #10 from Tom O'Connor <toconnor at forcepoint dot com> --- In regards to GDB, I noticed that when using a macro to get the offset for these bitfields, with objects built by both GCC 5 and earlier as well as GCC 6, I always get 0. For example: (gdb) macro define offsetof(t, f) &((t *) 0)->f) (gdb) p offsetof(struct s, type) $1 = (unsigned int *) 0x0 Historically, prior to GCC 6, this always matched up with DWARF's DW_AT_data_member_location value for bitfields. Yes, I see how GCC 6's combination of data_member_location and bit_offset can be combined to reach the true location. Historically, my use case has used the data_member_location value to get me the offset into say a raw memory image, for where to start reading data from a field of a structure in memory; I'd do bitfield shifts after reading from the aligned offset as reported in the DWARF structure. If using DECL_BIT_FIELD_REPRESENTATIVE as data_member_location is nicer and doesn't break the Ada use case, I'd be all for that. But if what's currently being emitted by GCC 6 is considered "more correct" than what previous versions had emitted, then I'll have to adjust. I only noticed the change between 5 and 6 once I started seeing odd results with the same code built by different GCCs.
