Hi Martin, On Sun, Mar 24, 2024 at 11:11:21AM -0300, Martin Rodriguez Reboredo wrote: > On 3/20/24 19:52, Mark Wielaard wrote: > >Could you show an example of when/where you need it and what address > >you set it to? > > For example, this test program reports the name and location pointed by > the passed address. > > $ ./report /home/yakoyoku/.debug/.build-id/.../elf 0x0003281f > 0x000000000003281f > ?? > ??:0 > > But due to the mentioned bias both of them are unknown or out of range. > > >The offline_next_address is only relevant for ET_REL files (like > >object files or kernel modules). In general you will need to check the > >bias, which various dwfl functions return to know the difference > >between the addresses in the ELF, Dwarf or the module load address. > > > >That said, readelf, nm and dwfl_argp do "cheat" by setting the > >offline_next_address to zero if they know they are just inspecting a > >single object file. So maybe this is a functionality we need to > >expose. But I don't fully understand why you need both a getter and a > >setter for any arbitrary address. > > I've erroneously thought that setting `offline_next_address` was a > requirement to obtain what I've needed. But if I use > `dwfl_module_getelf` or `dwfl_module_getdwarf` I can get the correct > name and location. > > 0x000000000003281f > _ZNSt11__copy_moveILb0ELb0ESt26random_access_iterator_tagE8__copy_mIPcPhEET0_T_S6_S5_ > /usr/include/c++/13.2.1/bits/stl_algobase.h:388,18 > > So this patch is kinda pointless, but at least I've managed to learn > what I was missing. Anyways, thanks for the heads-up. :)
I don't think it was pointless. Clearly our documentation is not very good (and given eu-readelf and eu-nm do cheat, maybe our interface/api isn't really good either). Maybe you could post your code for that ./report program and what you had to do to get it to print the correct address/symbols. Then we at least have some documentation for others which hit the same issue. Thanks, Mark
