[Monotone-devel] illegal instruction [was Re: Problem with build of monotone 0.11 on Debian testing]

[graydon hoare]

Joel Rosdahl wrote:

> monotone on my machine running Debian testing. Compilation and linking
> work, but the test suite bombs out. I also fail to netsync with
> off.net with my own compiled version. The .deb provided on
> http://www.venge.net/monotone/ works perfectly, though.
>
> The errors I see are "illegal instruction" crashes. I don't think I
> have a hardware problem, since I don't experience any similar problems
> with other programs (like gcc or monotone from your .deb, for
> example).

yeah, the problem is with -msse2. it's generating SSE2 (vector) code and 
your hardware doesn't support it. you wouldn't happen to be using an 
athlon, would you?

if you build without the -msse2 flag you should be in business. the 
reason it "works" when you remove the trust hook is that you aren't 
invoking the crypto system at all, so it doesn't hit the illegal 
instruction paths. so I built the release without -msse2.

I'm looking into ways of making the activation of the SSE2 code "more 
automatic". I thought I had it pinned down by the release -- the path I 
thought it was constrained to does a CPUID test -- but then I moved what 
I thought was working code to my athlon for testing, and got the error 
you're seeing. I think gcc might spontaneously *generate* some SSE2 code 
when you say -msse2, or else perhaps I am just doing CPUID in a way 
which makes athlons angry.

sorry for the confusion. I'm CC'ing this reply to our mailing list in 
case anyone else runs into the problem.

-graydon