On Thu, Jan 17, 2019 at 6:14 AM Tom de Vries <tdevr...@suse.de> wrote: > > On 17-01-19 01:35, Ian Lance Taylor wrote: > > On Wed, Jan 16, 2019 at 4:17 PM Tom de Vries <tdevr...@suse.de> wrote: > >> > >> this handles DW_FORM_GNU_ref_alt which references the .debug_info > >> section in the .gnu_debugaltlink file. > >> > >> OK for trunk? > >> > >> Thanks, > >> - Tom > >> > >> On 11-12-18 11:14, Tom de Vries wrote: > >>> 2018-12-10 Tom de Vries <tdevr...@suse.de> > >>> > >>> * dwarf.c (enum attr_val_encoding): Add ATTR_VAL_REF_ALT_INFO. > >>> (struct unit): Add low and high fields. > >>> (struct unit_vector): New type. > >>> (struct dwarf_data): Add units and units_counts fields. > >>> (read_attribute): Handle DW_FORM_GNU_ref_alt using > >>> ATTR_VAL_REF_ALT_INFO. > >>> (find_unit): New function. > >>> (find_address_ranges): Add and handle unit_tag parameter. > >>> (build_address_map): Add and handle units_vec parameter. > >>> (read_referenced_name_1): Handle DW_FORM_GNU_ref_alt. > >>> (build_dwarf_data): Pass units_vec to build_address_map. Store > >>> resulting > >>> units vector. > > > > > >>> @@ -281,6 +283,10 @@ struct unit > >>> /* The offset of UNIT_DATA from the start of the information for > >>> this compilation unit. */ > >>> size_t unit_data_offset; > >>> + /* Start of the compilation unit. */ > >>> + size_t low; > >>> + /* End of the compilation unit. */ > >>> + size_t high; > > > > The comments should say what low and high are measured in, which I > > guess is file offset. Or is it offset from the start of UNIT_DATA? > > Either way, If that is right, then the fields should be named > > low_offset and high_offset. Otherwise it seems easy to confuse with > > function_addrs, where low and high refer to PC values. > > > > Done. > > > Also if they are offsets from UNIT_DATA then size_t is OK, but if the > > are file offsets they should be off_t. > > > > AFAIU, in the case where off_t vs size_t would make a difference, we're > running into trouble much earlier. I've filed PR 88890 - "libbacktrace > on 32-bit system with _FILE_OFFSET_BITS == 64" ( > https://gcc.gnu.org/bugzilla/show_bug.cgi?id=88890 ) about this. > > Anyway, I've made the conservative choice of using off_t for now (but I > could argue that it's a memory offset, given that the assumption is that > the entire debug section is read into memory).
Since the entire debug section is read into memory, if they are offsets from UNIT_DATA, they should be size_t, not off_t. I wasn't trying to say that we should make a conservative choice here, I was trying to say that we should make a correct choice. An offset from UNIT_DATA should be size_t, a file offset should be off_t. Ian
