hashes_examples crashes with "Bus Error" (unaligned access) on sparc64

[glaubitz]

The hashes_examples binary crashes with "Bus Error" on sparc64, most likely caused by unaligned access:

bin/nim doc --hint[Conf]:off --hint[Path]:off --hint[Processing]:off -d:boot --putenv:nimversion=1.0.99  --git.url:https://github.com/nim-lang/Nim -o:web/upload/1.0.99/osproc.html --index:on lib/pure/osproc.nim
bin/nim doc --hint[Conf]:off --hint[Path]:off --hint[Processing]:off -d:boot --putenv:nimversion=1.0.99  --git.url:https://github.com/nim-lang/Nim -o:web/upload/1.0.99/pegs.html --index:on lib/pure/pegs.nim
bin/nim doc --hint[Conf]:off --hint[Path]:off --hint[Processing]:off -d:boot --putenv:nimversion=1.0.99  --git.url:https://github.com/nim-lang/Nim -o:web/upload/1.0.99/dynlib.html --index:on lib/pure/dynlib.nim
bin/nim doc --hint[Conf]:off --hint[Path]:off --hint[Processing]:off -d:boot --putenv:nimversion=1.0.99  --git.url:https://github.com/nim-lang/Nim -o:web/upload/1.0.99/strscans.html --index:on lib/pure/strscans.nim
bin/nim doc --hint[Conf]:off --hint[Path]:off --hint[Processing]:off -d:boot --putenv:nimversion=1.0.99  --git.url:https://github.com/nim-lang/Nim -o:web/upload/1.0.99/parseopt.html --index:on lib/pure/parseopt.nim
bin/nim doc --hint[Conf]:off --hint[Path]:off --hint[Processing]:off -d:boot --putenv:nimversion=1.0.99  --git.url:https://github.com/nim-lang/Nim -o:web/upload/1.0.99/hashes.html --index:on lib/pure/hashes.nim
Hint: used config file '/home/glaubitz/nim/Nim/config/nim.cfg' [Conf]
Hint: used config file '/home/glaubitz/nim/Nim/config/config.nims' [Conf]
Hint: operation successful (7730 lines compiled; 0.442 sec total; 12.422MiB peakmem; Debug Build) [SuccessX]
Hint: /home/glaubitz/.cache/nim/hashes_d/runnableExamples/hashes_examples  [Exec]
Bus error
Error: execution of an external program failed: '/home/glaubitz/.cache/nim/hashes_d/runnableExamples/hashes_examples '
[Examples] failed: see /home/glaubitz/.cache/nim/hashes_d/runnableExamples/hashes_examples.nim

glaubitz@kyoto:~/nim/Nim$

And the backtrace:

glaubitz@kyoto:~/nim/Nim$ /home/glaubitz/.cache/nim/hashes_d/runnableExamples/hashes_examples
Bus error
glaubitz@kyoto:~/nim/Nim$ gdb /home/glaubitz/.cache/nim/hashes_d/runnableExamples/hashes_examples
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License GPLv3+: GNU GPL version 3 or later <http://gnu.org/licenses/gpl.html>
This is free software: you are free to change and redistribute it.
There is NO WARRANTY, to the extent permitted by law.
Type "show copying" and "show warranty" for details.
This GDB was configured as "sparc64-linux-gnu".
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Reading symbols from /home/glaubitz/.cache/nim/hashes_d/runnableExamples/hashes_examples...
(No debugging symbols found in /home/glaubitz/.cache/nim/hashes_d/runnableExamples/hashes_examples)
(gdb) r
Starting program: /home/glaubitz/.cache/nim/hashes_d/runnableExamples/hashes_examples

Program received signal SIGBUS, Bus error.
0x00000100000135f8 in murmurHash__CiCiZV9c7F9alrF1xV3QD1ag ()
(gdb) bt
#0  0x00000100000135f8 in murmurHash__CiCiZV9c7F9alrF1xV3QD1ag ()
#1  0x0000010000013f78 in hash__2f0mDKnzcXGyxkdkc7DbDw ()
#2  0x0000010000015c60 in unknown_hashes_examples3Init000 ()
#3  0x00000100000170d8 in PreMainInner ()
#4  0x0000010000017160 in PreMain ()
#5  0x00000100000171a4 in NimMain ()
#6  0x0000010000017248 in main ()
(gdb)

[FedericoCeratto]

Link to the latest build: https://buildd.debian.org/status/fetch.php?pkg=nim&arch=sparc64&ver=1.0.6-1&stamp=1580775897&raw=0

[glaubitz]

This should be easy to bisect or trace with GDB, but I haven't gotten around doing this yet.

[Araq]

No need, we know it's caused by our newer faster hash function implementation.

[glaubitz]

Would it be possible to fix this unaligned access?

While it doesn't crash on other non-x86 architectures, it will certainly degrade performance there since the unaligned access must be handled by the kernel in many cases.

[Araq]

Sure, a fix is in the works.

[glaubitz]

It seems I cannot reproduce the Bus Error on git master anymore anyway.

I ran sh ./build_all.sh and ./koch doc but don't see any crashes.

And running ./koch tests exits early with tests failed and lots of usage messages from the testament command.

[FedericoCeratto]

Tested when defined(js) or defined(sparc) or defined(sparc64): with nim doc ... lib/pure/hashes.nim successfully on kyoto.debian.net (UltraSparc T2) using Nim 1.0.6.

It needs the sparc64 define. I'm not sure if we need to support the sparc define.

[glaubitz]

The “sparc” define would be required for the Gentoo folks who use 32-bit SPARC.

[FedericoCeratto]

Update: all the nim doc tests passed without other changes.