What steps will reproduce the problem?

package main

import "sync/atomic"

func main() {
        atomic.CompareAndSwapUint32(nil, 0, 0)
}

What is the expected output? What do you see instead?

Expected:

panda(~/src) % go run nil.go
panic: runtime error: invalid memory address or nil pointer dereference
[signal 0xb code=0x1 addr=0x0 pc=0x31980]

goroutine 16 [running]:
runtime.panic(0x34578, 0x65120)
    /home/dfc/go/src/pkg/runtime/panic.c:250 +0x138
sync/atomic.CompareAndSwapUint32(0x0, 0x0, 0x0)
    ?:0 +0x8
main.main()
    /home/dfc/src/nil.go:6 +0x3c
exit status 2

Got:

runtime: unexpected return pc for runtime.main called from 0xffffffff
fatal error: unknown caller pc

runtime stack:
runtime.throw(0x6cf49)
        /usr/home/dfc/go/src/pkg/runtime/panic.c:464 +0x5c
runtime.gentraceback(0x1cd90, 0x5026dec0, 0x0, 0x3016c0a0, 0x0, ...)
        /usr/home/dfc/go/src/pkg/runtime/traceback_arm.c:105 +0x2f0
addstackroots(0x3016c0a0, 0xbfffea04)
        /usr/home/dfc/go/src/pkg/runtime/mgc0.c:1645 +0x184
markroot(0x30190000, 0x5)
        /usr/home/dfc/go/src/pkg/runtime/mgc0.c:1342 +0xf8
runtime.parfordo(0x30190000)
        /usr/home/dfc/go/src/pkg/runtime/parfor.c:105 +0xc0
gc(0x5026dedc)
        /usr/home/dfc/go/src/pkg/runtime/mgc0.c:2335 +0x1cc
mgc(0x3016c0a0)
        /usr/home/dfc/go/src/pkg/runtime/mgc0.c:2281 +0x30
runtime.mcall(0x6f86c)
        /usr/home/dfc/go/src/pkg/runtime/asm_arm.s:163 +0x3c

goroutine 16 [garbage collection]:
runtime.gc(0x0)
        /usr/home/dfc/go/src/pkg/runtime/mgc0.c:2250 +0x1b8 fp=0x5026dee4
runtime.mallocgc(0x20, 0x0, 0x0)
        /usr/home/dfc/go/src/pkg/runtime/malloc.goc:213 +0x18c fp=0x5026df24
runtime.mal(0x14)
        /usr/home/dfc/go/src/pkg/runtime/malloc.goc:833 +0x38 fp=0x5026df34
runtime.panic(0x39668, 0x6cb28)
        /usr/home/dfc/go/src/pkg/runtime/panic.c:217 +0x2c fp=0x5026df54
runtime.panicstring(0x6cb28)
        /usr/home/dfc/go/src/pkg/runtime/panic.c:482 +0xac fp=0x5026df68
runtime.sigpanic()
        /usr/home/dfc/go/src/pkg/runtime/os_freebsd.c:193 +0x108 fp=0x5026df74
sync/atomic.armCompareAndSwapUint32(0x0, 0x0, 0x0)
        /usr/home/dfc/go/src/pkg/sync/atomic/asm_arm.s:14 +0x4 fp=0x5026df78
runtime.main()
        /usr/home/dfc/go/src/pkg/runtime/proc.c:231 +0xf8 fp=0x5026dfac
runtime: unexpected return pc for runtime.main called from 0xffffffff
runtime.main()
        /usr/home/dfc/go/src/pkg/runtime/proc.c:231 +0xf8 fp=0x5026dfe0
created by _rt0_go
        /usr/home/dfc/go/src/pkg/runtime/asm_arm.s:72 +0xb0

goroutine 17 [runnable]:
runtime.MHeap_Scavenger()
        /usr/home/dfc/go/src/pkg/runtime/mheap.c:507
runtime.goexit()
        /usr/home/dfc/go/src/pkg/runtime/proc.c:1438
exit status 2

Please use labels and text to provide additional information.

http://build.golang.org/log/4d58a23a098e04703e8a487ca572ddecf3b6bd0a
http://build.golang.org/log/8c3d576a9e243aa1f7ddf53fdcb8e12c11eb85aa