go appears to not support i386 CPUs lacking SSE

[he32]

What version of Go are you using (go version)?

1.8 (or, rather, trying to run)
This is a pre-built binary package, i.e. it's not built from source on this host.

What operating system and processor architecture are you using (go env)?

NetBSD/i386 7.1

This is a true i386 CPU:

cpu0: Intel Celeron (Covington) (686-class), 331.13 MHz
cpu0: family 0x6 model 0x5 stepping 0x1 (id 0x651)
cpu0: features 0x183f9ff<FPU,VME,DE,PSE,TSC,MSR,PAE,MCE,CX8,SEP,MTRR,PGE,MCA>
cpu0: features 0x183f9ff<CMOV,PAT,PSE36,MMX,FXSR>

As such it has MMX but not SSE, as seen above.

What did you do?

Try to run / use go, e.g. "go version".
Watch it crash and burn with "Illegal instruction".

Examining the core dump reveals:
...
eip 0x807937b 0x807937b <runtime.check+27>
...
(gdb) x/i 0x807937b
=> 0x807937b <runtime.check+27>: xorps %xmm0,%xmm0
(gdb)

What did you expect to see?

1.8

What did you see instead?

Illegal instruction (core dumped)

Now, I realize I'm strictly in the minority here with such an old CPU, and it
may be that go insists on a newer CPU with SSE support.

[ALTree]

Does this happen if you set GO386=387 ? I.e.

$ env GO386=387 go build ...

so after building something with 387 (if you have a working version of go on that machine). It shouldn't. If nothing crashes the problem is in your pre-build binary, you'll have to build from source with GO386=387 set to build with support for MMX cpus.

[he32]

Does this happend if you set `GO386=387` ? I.e. ``` $ env GO386=387 go version ```

Yes, that still happens: # env GO386=387 go version Illegal instruction (core dumped) # Regards, Håvard

[ALTree]

Sorry I edited that message but github sent the mail too fast.

We do support MMX cpus via the GO386 env variable. Doc says we auto-detect it, so if you downloaded a pre-build go toolchain that was build on a SSE2 machine it'll contain SSE2 instructions and the go version crash on your machine is expected.

You'll have to build the toolchain from source on your MMX machine.

[he32]

Hmm, ok., I'll try to build it on this host.
However, this looks like a missing separation of target and host/build information...

[ALTree]

Not really: when cross-compiling you can tune everything you need with env variables. Your problem is that if nothing is set we have to default to something; and we default to what the building machine supports. I believe this is a sensible choice.

[ALTree]

I'm closing this since it appears that the crash is caused by a toolchain that was not compiled for your 386 machine (so there's no bug). Please comment if you think you found a bug, and we'll reopen. Thanks.

[he32]

Not really: when cross-compiling you can tune everything you need with env variables. Your problem is that if nothing is set we have to default to *something*; and we default to what the building machine supports. I believe this is a sensible choice.

OK, then I may have a nit to pick with the packaging system, and I'll need to look into what can be set to tune the build.