>    int segment;			/* Index of first segment table entry.  */
>    bool gc;			/* Mark/sweep flag.  */
> +  bool is_executable : 1;	/* Use Dwfl::executable_for_core?  */

If you're going to use a bitfield, then make every other bool in that
struct a bitfield too.  But it's not usually worthwhile.  It's
premature microoptimization that privileges memory over CPU, which
might not even be the right tradeoff any more.