Daniel Jacobowitz writes: > On Fri, Jul 13, 2007 at 11:08:15AM +0100, Andrew Haley wrote: > > > > I can work around some of the failures, but I can't really be > > > > bothered: the real fix for this is EABI. > > > > > > Unfortunately, the EABI won't fix this either. In its native form it > > > supported neither forced unwinding nor _Unwind_Backtrace; we added > > > forced unwinding for the benefit of NPTL (though we're still talking > > > to ARM intermittently about its semantics). But no one's tried to > > > make _Unwind_Backtrace work yet, and it's not clear how to. To me > > > anyway. > > > > Interesting. Presumably there is enough information in the unwinder > > data to do it? If it's technically impossible to do a simple > > backtrace then I have to wonder what the point of the EABI is. > > The data is there, but it's not structured the right way. In > .eh_frame unwinding, there's a standard format to define saved > registers and an augmentation to define the language-specific data and > the personality routine which understands that language-specific data. > In ARM EABI unwinding, the personality routine is responsible for > reading the saved register data as well as the language specific > data. So the core unwinder (_Unwind_* in libgcc) is limited in what > it can do by the flags accepted by the personality routines. > > There are several standard formats defined by the EHABI. GCC only > ever uses those. But we might not have our own implementations of the > personality routines, so we can't ABI-conformantly pass them invalid > flags. We play a little loose with this for forced unwinding and let > ourselves sleep at night since we proposed standardization language > for them to ARM :-)
OK. Can you send me a copy of your proposed standardization language? > However, for the standard table formats and personality routines, we > could arrange to do backtraces anyway. It should be just a matter of > a day's work or so and a little more code in the unwinder, and it > would work with all GCC-compiled code with unwind info. Thanks. I'm busy for the next week or so, but I might be able to get back to it after then, depending on hardware availability. Andrew. -- To UNSUBSCRIBE, email to [EMAIL PROTECTED] with a subject of "unsubscribe". Trouble? Contact [EMAIL PROTECTED]
