Am 01.10.2019 um 10:39 hat Vladimir Sementsov-Ogievskiy geschrieben: > 30.09.2019 19:39, Kevin Wolf wrote: > > Am 30.09.2019 um 18:26 hat Vladimir Sementsov-Ogievskiy geschrieben: > >> 30.09.2019 19:00, Kevin Wolf wrote: > >>> Am 30.09.2019 um 17:19 hat Vladimir Sementsov-Ogievskiy geschrieben: > >>>> 30.09.2019 18:12, Kevin Wolf wrote: > >>>>> Am 24.09.2019 um 22:08 hat Vladimir Sementsov-Ogievskiy geschrieben: > >>>>>> Here is introduced ERRP_FUNCTION_BEGIN macro, to be used at start of > >>>>>> functions with errp parameter. > >>>>> > >>>>> A bit of bike shedding, but FOO_BEGIN suggests to me that a FOO_END will > >>>>> follow. Can we find a different name, especially now that we won't use > >>>>> this macro in every function that uses an errp, so even the "errp > >>>>> function" part isn't really correct any more? > >>>>> > >>>>> How about ERRP_AUTO_PROPAGATE? > >>>> > >>>> I have an idea that with this macro we can (optionally) get the whole > >>>> call stack > >>>> of the error and print it to log, so it's good to give it more generic > >>>> name, not > >>>> limited to propagation.. > >>> > >>> Hm, what's the context for this feature? > >>> > >>> The obvious one where you want to have a stack trace is &error_abort, > >>> but that one crashes, so you get it automatically. If it's just a normal > >>> error (like a QAPI option contains an invalid value and some function > >>> down the call chain checks it), why would anyone want to know what the > >>> call chain in the QEMU code was? > >>> > >> > >> When I have bug from testers, call stack would be a lot more descriptive, > >> than just > >> an error message. > >> > >> We may add trace point which will print this information, so with disabled > >> trace point > >> - no extra output. > > > > But wouldn't it make much more sense then to optionally add this > > functionality to any trace point? I really don't see how this is related > > specifically to user-visible error messages. > > Interesting idea > > > > > However, even if we decide that we want to have this in Error objects, > > wouldn't it make much more sense to use the real C stack trace and save > > it from the innermost error_set() using backtrace() or compiler > > built-ins rather than relying on an error_propagate() chain? > > > Hmm, I thought about this.. And in concatenation with the fact that > we'll have macro not everywhere, backtrace may be better.. > > On the other hand, backtrace will not show coroutine entries..
Hm, good point. I wonder if we can easily get a stack trace not starting at the current point, but from a jmp_buf. Then we could just switch to the coroutine caller whenever we reach coroutine_trampoline(). But glibc doesn't seem to support this case easily, so that might mean rewriting all of the stack unwinding inside QEMU... Maybe not then. > OK, anyway, if we will track some additional information in > trace-events or in macros or in error_* API functions, it's not bad to > track some additional information in macro named ERRP_AUTO_PROPAGATE. Yes, I think tracking the information where we use ERRP_AUTO_PROPAGATE anyway is okay. I just wouldn't add the macro everywhere just for the sake of the additional information. Kevin
