https://gcc.gnu.org/bugzilla/show_bug.cgi?id=91239
--- Comment #8 from Jakub Jelinek <jakub at gcc dot gnu.org> --- The .debug_macro deduplication works by computing a checksum of the ops coming from certain headers (define, undef entries mostly) and not interrupted by entries from other headers (e.g. if stdio.h has 10 define/undef directives, then include some other header that has 20 define/undef directives, then stdio.h has another 30 define/undef directives, there will be 3 comdat sections, 2 with wm4.stdio.h.* name (with the hash after it) and one for the other header). The DW_MACRO_import operands always refer to the start of such comdat section. Except for the ignored case of a hash collision, the intended behaviro is that if out of say 50 copies of wm4.stdio.h.24.5c1b97eef3c86b7a2549420f69f4f128 one is kept and the 49 are left out, all the references are adjusted to the start of the copy that is left in the ELF object.
