What steps will reproduce the problem?

don't have code to reliably reproduce this yet.

we have a map of the form

map[uint32]*someStruct

the map is usually quite small. the map instances usually live in an array
[30]map[uint32]*someStruct in our program.

we sometimes range over the map and delete all its keys. unnecessary, but anyway. this
crashes.

there's no concurrency in this code, so I don't think this is a data race.

What do you see instead?

two crashes:

unexpected fault address 0x9001001c
fatal error: fault
[signal 0xb code=0x1 addr=0x9001001c pc=0x410e5e]
goroutine 1 [running]:
[fp=0x7f2e698674a0] runtime.throw(0x17c4337)
/build/go/go/src/pkg/runtime/panic.c:473 +0x67
[fp=0x7f2e698674b8] runtime.sigpanic()
/build/go/go/src/pkg/runtime/os_linux.c:239 +0xe7
[fp=0x7f2e698674d8] hash_iter_init(0xcbb3a0, 0x90010010, 0x7f2e69867580)
/build/go/go/src/pkg/runtime/hashmap.c:779 +0x2e
[fp=0x7f2e69867500] runtime.mapiterinit(0xcbb3a0, 0x90010010, 0x7f2e69867580)
/build/go/go/src/pkg/runtime/hashmap.c:1364 +0x4b

unexpected fault address 0x0
fatal error: fault
[signal 0xb code=0x80 addr=0x0 pc=0x410e5e]
goroutine 1 [running]:
[fp=0x7f666549d4a0] runtime.throw(0x17c4337)
/build/go/go/src/pkg/runtime/panic.c:473 +0x67
[fp=0x7f666549d4b8] runtime.sigpanic()
/build/go/go/src/pkg/runtime/os_linux.c:239 +0xe7
[fp=0x7f666549d4d8] hash_iter_init(0xcb7620, 0x210008b12050000, 0x7f666549d580)
/build/go/go/src/pkg/runtime/hashmap.c:779 +0x2e
[fp=0x7f666549d500] runtime.mapiterinit(0xcb7620, 0x210008b12050000, 0x7f666549d580)
/build/go/go/src/pkg/runtime/hashmap.c:1364 +0x4b

Which compiler are you using (5g, 6g, 8g, gccgo)?

6g

Which operating system are you using?

linux

Which version are you using?  (run 'go version')

go version go1.1.2 linux/amd64