[LLVMdev] ARM unwinding bug (original) (raw)

Ben Pye ben at curlybracket.co.uk
Wed Jul 29 14:20:14 PDT 2015

Yes, so, that's yet another missing info. Which ARM? RaspberyPi, although popular, is a very old and somewhat deprecated architecture (ARMv6). Most people work on ARMv7 and ARMv8 nowadays, so if you can't reproduce the bugs on those, you'll have a hard time finding people to help you.

Also, Clang 3.6 is not that old, but we don't really provide maintenance to non-trunk versions of the compiler, so if you want a bug looked into, you need to reproduce it in trunk. If you can't, than the problem is fixed, and you either wait for the new release to come out, or build your own from trunk.

Not sure if you got the other message, I think I managed to split the topic as I wasn't subscribed to receive the previous message. This error has been on the Raspberry Pi 2, so that's a Cortex A7 I believe, certainly ARMv7. I haven't yet built trunk as on the device I run out of memory and do not have enough disk space to allocate a large enough swap space, and it's too slow to wait for it to fail, so I'd have to cross compile which is not something I have yet attempted, unfortunately LLVM/Clang only provides AMD64 packages for nightly builds, despite building it for a vast matrix.

I don't believe this to be an unwinder bug, but a generation bug (of the unwind information). I do find the crash you experience curious, but it's not something I have had occur here. Unfortunately I can't say I have great experience with the ARM unwind information, but really got to that conclusion by eliminating libunwind as GCC does generate unwind information that results in PC being restored.

I'll update the bug with some more info, but you need to reproduce it in trunk and in a hardware that I have access to. RPI is just not relevant enough for me, that I don't even have one. Perhaps I should buy one...

I think you could reproduce this on scaleway.io 's hosted service, which offer a free month, but I'd be happy to provide access to something if that's what it took. As I said though, RPi 2 should be a pretty vanilla Cortex A7 core.

Ben. -------------- next part -------------- An HTML attachment was scrubbed... URL: <http://lists.llvm.org/pipermail/llvm-dev/attachments/20150729/3c7c4e91/attachment.html>

More information about the llvm-dev mailing list