> Date: Tue, 27 Nov 2012 19:43:40 +0100 (CET) > From: "Ulrich Weigand" <uweig...@de.ibm.com> > > Mark Kettenis wrote: > > > Date: Mon, 26 Nov 2012 20:10:06 +0100 (CET) > > > From: "Ulrich Weigand" <uweig...@de.ibm.com> > > > > > > Hello, > > > > > > I noticed what appears to be a long-standing bug in generating > > > .dwarf_frame > > > sections with GCC on Linux on PowerPC. > > > > > > ... > > > > > > So I'm wondering where to go from here. I guess we could: > > > > > > 1. Bring GCC (and gas) behaviour in compliance with the documented ABI > > > by removing the #undef DBX_REGISTER_NUMBER and changing gas's > > > md_reg_eh_frame_to_debug_frame to the original implementation from > > > Jakub's patch. That would make GDB work well on new files, but > > > there are a large number of binaries out there where we continue > > > to have the same behaviour as today ... > > > > > > 2. Leave GCC and gas as-is and modify GDB to expect GCC numbering in > > > .dwarf_frame, except for the condition code register. This would > > > break debugging of files built with GCC 4.0 and 4.1 unless we > > > want to add a special hack for that. > > > > > > 3. Like 2., but remove the condition code hack: simply use identical > > > numbers in .eh_frame and .dwarf_frame. This would make PowerPC > > > like other Linux platforms in that respect. > > > > > > Thoughts? > > > > What do other compilers (in particular XLC) do? From a GDB standpoint > > it would be a major PITA if different compilers would use different > > encodings for .dwarf_frame. > > In my tests XLC (version 12.1 on Linux) seems to consistently use the > GCC register numbering in both .eh_frame and .dwarf_frame. LLVM also > consistently uses the GCC register numbering. Looks like this would > be another argument for variant 3 ...
Probably. Certainly the most practical solution. Although I'd say that the fact that people have been able to live with the non-matching register numbering schemes for so many years means that variant 1 wouldn't hurt people too badly. It's a bit of a shame that on one of the few architectures that bothered to provide a definition of the DWARF register numbers we wouldn't use it :(.
