In regards to debug symbols on the stable branch: All i can say for sure is the debug symbols are being stripped right now with LTO enabled by default, and they aren't stripped if you pass `--no-lto`. I wouldn't have expected LTO to work this way, but this is our observation and one of the reason's we're going to disable it by default.
-- Dr. Bobby R. Bruce Room 3050, Kemper Hall, UC Davis Davis, CA, 95616 web: https://www.bobbybruce.net On Mon, May 24, 2021 at 1:43 PM Gabe Black <gabe.bl...@gmail.com> wrote: > I don't think LTO strips debug symbols... But yes, LTO does significantly > increase link time if your machine doesn't have lots of cores to > parallelize the link. It slows it down in general, but with gcc you can > parallelize the link with LTO where you can't without LTO for some reason, > and that outweighs the other overhead if you have enough cores to throw at > it. > > Especially when running in a virtual machine, you might just be running > out of memory. LTO will use more ram, and if you run out things will fail > in potentially strange ways. > > It sounds like you have a workaround for now so this may be a moot point, > but in general, when you report compiler errors (or errors in general) it's > very helpful to provide the error output instead of just describing the > errors. That provides a lot of helpful detail which can make diagnosing the > problem much easier. > > Gabe > > On Mon, May 24, 2021 at 1:07 PM Bobby Bruce via gem5-users < > gem5-users@gem5.org> wrote: > >> Thanks for the report Eliot. In this case there's no need to file a bug >> report as we're about to produce a minor release of gem5 that will off LTO >> by default. I'm not familiar with this particular problem you are facing, >> but we've found we need to turn it off for other reasons (1. It increases >> links times for some users to unacceptable levels and 2. LTO strips debug >> symbols which you'll need if you want to run tools such as GDB). >> >> I'm hoping we can ship the minor release sometime this week! >> >> -- >> Dr. Bobby R. Bruce >> Room 3050, >> Kemper Hall, UC Davis >> Davis, >> CA, 95616 >> >> web: https://www.bobbybruce.net >> >> >> On Mon, May 24, 2021 at 12:43 PM Eliot Moss via gem5-users < >> gem5-users@gem5.org> wrote: >> >>> Dear Gem5-ers: >>> >>> I have been trying to build Gem5 out of the box, for x86, on a VirtualBox >>> virtual machine set up for 64-bit Ubuntu 20.04 ("focal"). I can do >>> >>> scons build/X86/gem5.opt >>> >>> but it will succeed only if I disable link time optimization LTO using >>> --no-lto. I've tried various versions GCC - 7, 8, 9, and 10 - and all >>> produce the same result. (I think the key thing is probably something in >>> binutils, but I don't know what version to try to obtain, and this >>> version of >>> Ubuntu does not readily offer anything other than 2.34.) >>> >>> Searching the web about this general problem mostly produces the >>> "solution" of >>> disabling LTO. So, where should we / I file a bug report? By turning >>> on LTO >>> reporting, I have found that the proximal cause is that decoder.o does >>> not >>> have a .debug_str section and yet there are a huge number of references >>> to >>> things that should be there (labels, I guess - the decode *would* have a >>> lot >>> of those!). >>> >>> Regards - Eliot >>> _______________________________________________ >>> gem5-users mailing list -- gem5-users@gem5.org >>> To unsubscribe send an email to gem5-users-le...@gem5.org >>> %(web_page_url)slistinfo%(cgiext)s/%(_internal_name)s >>> >> _______________________________________________ >> gem5-users mailing list -- gem5-users@gem5.org >> To unsubscribe send an email to gem5-users-le...@gem5.org >> %(web_page_url)slistinfo%(cgiext)s/%(_internal_name)s > >
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