Using std::unstable::intrinsics::uninit() causes voidBroken module found

[colemickens]

I modified some code from this

let filter_program: bpf_program;
if handle == ptr::null() {
    None
} else {
    pcap_lookupnet(dev, &netp, &maskp, eb);
    let res = pcap_compile(handle, &filter_program, filter_str, 0, &netp);
    [...]
}

to this:

let filter_program: bpf_program = std::unstable::intrinsics::uninit();
if handle == ptr::null() {
    None
} else {
    pcap_lookupnet(dev, &netp, &maskp, eb);
    let res = pcap_compile(handle, &filter_program, filter_str, 0, &netp);
    [...]
}

to attempt to avoid: "error: use of possibly uninitialized variable: filter_program" as per @cmr's suggestion.

Now the compiler is telling me:

Found return instr that returns non-void in Function of void return type!
  ret %"enum.rustpcap::bpf_program" undef
 voidBroken module found, compilation aborted!
Stack dump:
0.      Running pass 'Module Verifier' on function '@_ZN8unstable10intrinsics6uninit19hb2289098237644e0az4v0.0E'
[1]    2448 abort (core dumped)  rustc main.rs

[colemickens]

enum v {}
fn main() {
    let y: v = unsafe { std::unstable::intrinsics::uninit() };
}

is apparently a simpler repro case.

[alexcrichton]

This appears to be fixed now, flagging needstest