Yeah, this sounds tricky, but it is actually good timing, because I was just about to start working on DWP v5 in lldb. I was hoping that would be an easy ride, but it looks like things will get complicated.
On Tue, 25 Feb 2020 at 18:53, David Blaikie <dblai...@gmail.com> wrote: > > (please add anyone who has a vested interest in Split DWARF in general and > dwp in particular) > > tl;dr: > How should DWARFv4 and DWARFv5 coexist in a DWP file: > 1) Not at all (invalid/unsupported) > 2) Single index table where the section indexes are subjective (look at the > version of the referenced CU/TU to decide what a column number means (eg: 8 > is DW_SECT_MACRO in v4, DW_SECT_RNGLISTS in v5) > 3) Emit multiple indexes (cu_index and tu_index each would contain two > indexes) - a v4 (well, index version 2) and a v5 (index version 5) index. What about option 4)? :P Have the numbers be interpreted relative to the debug_cu_index version number? The idea would be that a DWARF v4 (dwp tool seems to use version number 2 for some reason) debug_cu_index would keep using the existing pre-standard scheme, and it would not be able to refer to v5 units. In a v5 debug_cu_index (*), we would use the official DWARF v5 scheme, *but* we would, as an extension, support referring to the pre-standard sections via custom DW_SECT constants (with some high numbers to avoid conflicting with future standard versions). (*) The v5 cu_index would be used whenever we have at least one v5 dwarf unit. Ignoring the section number mismatches, I think this is a reasonable approach, and it is the one I would make if I was in the shoes of the DWARF v6 committee and needed to make the debug_cu_index cover mixed-version units Speaking of DWARF v6, I think the debug_cu/tu_index sections are in need of some redesign anyway. For example, it's not clear to me how these sections would work in presence of DWARF64 -- all section offsets are hardcoded to 4 bytes, and we don't even have the initial_length mechanism to select bigger sizes. cheers, pavel _______________________________________________ Dwarf-Discuss mailing list Dwarf-Discuss@lists.dwarfstd.org http://lists.dwarfstd.org/listinfo.cgi/dwarf-discuss-dwarfstd.org
