Ensuring tests pass on gccgo

[Gustavo Niemeyer]

I apologize. After reading one of the review entries using
SameContents, I see I've misunderstood what the problem is about. The
v1 and v2 in your example is a slice, not a map, which means the test
is comparing slices of undefined order. This is certainly bogus and
needs addressing in the code itself, irrespective of any map-related
issues.

What I generally do in those cases is to define the ordering of the
slice. Besides enabling DeepEquals, it also makes the visual
comparison more pleasant.



On Thu, May 22, 2014 at 11:34 AM, Gustavo Niemeyer
<gustavo.niemeyer at canonical.com> wrote:
> On Wed, May 21, 2014 at 10:43 PM, Ian Booth <ian.booth at canonical.com> wrote:
>> We are working to make all juju-core unit tests pass using gccgo. In case you
>> didn't already know, there's a common issue which has caused a lot of the
>> failures to date. Here's a quick heads up on how to deal with it.
>>
>> golang-go and gcc-go have different map implementations which results in
>> ordering differences, affecting things like range etc (simplistically put,
>> gcc-go's map ordering is random whereas currently golang-go is somewhat
>> deterministic).
>
> This is changing in the main compiler as well, in Go 1.3:
>
>     http://tip.golang.org/doc/go1.3#map
>
> So it'll become even less deterministic there as well.
>
>> Now of course, maps are unordered but what we sometimes do in
>> the code is to use a map to hold some data (maybe to eliminate duplicates) and
>> then expose that data via a slice or array. If we then do a c.Assert(v1,
>> gc.DeepEquals, v2), it will fail on gcc-go, since the order of items in the 2
>> slices is different, even though the values are the same.
>
> If that's really the case, it's definitely a bug in gccgo. gocheck's
> DeepEquals is implemented in terms of reflect.DeepEqual, which should
> not care about the map order. In the standard library of the main
> compiler, it clearly does not:
>
>         for _, k := range v1.MapKeys() {
>                 if !deepValueEqual(v1.MapIndex(k), v2.MapIndex(k),
> visited, depth+1) {
>                         return false
>                 }
>         }
>
> So gocheck's DeepEquals is fine for such map tests, assuming no bugs
> in the underlying implementation.
>
>
> gustavo @ http://niemeyer.net



-- 
gustavo @ http://niemeyer.net