On Sat, Feb 24, 2024 at 03:00:04PM +0100, Mark Wielaard wrote: > Hi Omar, > > On Thu, Feb 22, 2024 at 05:03:44PM -0800, Omar Sandoval wrote: > > On Thu, Feb 22, 2024 at 04:53:19PM -0800, Omar Sandoval wrote: > > > On Fri, Feb 16, 2024 at 04:00:47PM +0100, Mark Wielaard wrote: > > > > Don't we also need to handle DW_SECT_LINE in dwarf_getsrclines and > > > > dwarf_next_lines when looking for DW_AT_stmt_list? > > > > > > .debug_line is the odd one out in split DWARF: the skeleton file > > > contains the full .debug_line, and the DWO or DWP files have a skeleton > > > .debug_line.dwo that only contains the directory and file name tables > > > (for DW_AT_file and macro info to reference). dwarf_getsrclines and co. > > > read from the skeleton file, not the DWP file, meaning they shouldn't > > > use DW_SECT_LINE. > > > > Ah, I guess you can call dwarf_getsrclines/dwarf_next_lines on the dwp > > file itself, where DW_SECT_LINE may be applicable. I need to think about > > that some more... > > So reading the DWARF5 spec, it says a split DWARF CU/TU DIE may have a > DW_AT_stmt_list, which are interpreted as relative to the base offset > for .debug_line.dwo. And these tables contain only the directory and > filename lists needed to interpret DW_AT_decl_file attributes in the > debugging information entries. Actual line number tables remain in the > .debug_line section, and remain in the relocatable object (.o) files. > > So I think the intention is that the main .debug_line (skeleton) > section does contain the actual line number table, but only those > file/dir table entries that are referenced from that. Not any that are > only referenced from the DW_AT_decl_file attributes (which should only > appear in the split DWARF DIEs). Maybe in practice these overlap > completely, so there is no savings and they are in practice > identical. But I don't see anything in the spec that implies you > should interpret a lineptr in the .debug_info.dwo as relative to the > .debug_line section in the skeleton.
Sorry, my reply was confusing, and I hadn't checked all of the relevant functions yet. Let me try again: As you said, the skeleton file has a .debug_line with the actual line number table, and the DWP file has a .debug_line.dwo with only file/directory name tables. If we're reading from the skeleton file, then we don't need to apply the DW_SECT_LINE offset. dwarf_getsrclines in particular always uses the skeleton's .debug_line even if called on a split CU, so it doesn't need to be updated. dwarf_getsrcfiles and dwarf_next_lines can use the split .debug_line.dwo, so they do need to be updated. Updated patch series incoming... Thanks, Omar
