Rework memory expansion/access in opFns

[axic]

Fixes #167. Depends on #175, #179, #186 and #188.

[axic]

This should work, but the reason it fails in some tests I think is because the VM is actually broken in those aspects, but the exception of bufferToInt masked those with an exceptional abort.

[jwasinger]

I believe the use of divRound is a problem here because we want to be rounding up to the next full word (i.e. ceil).

[axic]

Thanks for the review, but divRound is supposed to round up and also had an assertion for comparing the two versions. It might still be wrong, but most of the failures I've found weren't gas related, but plain crashes.

This PR is not finished and have found a lot of other bugs.

[jwasinger]

var BN = require('ethereumjs-util').BN

var x = new BN(20)
var y = new BN(15)
x = x.divRound(y)
console.log(x.toString())

gives

1

So it is clearly rounding down in this case.

[axic]

Hm, in that case the comparison was wrong, however if you look at the test results, there are plenty of other failures (number too big). Those I am in progress fixing.

[axic]

Down to these failures:

not ok 22 the state roots should match
not ok 714 the state roots should match
not ok 737 the state roots should match
not ok 753 the state roots should match
not ok 829 the state roots should match
not ok 1151 the state roots should match
not ok 1230 the state roots should match
not ok 1404 the state roots should match
not ok 2133 the state roots should match
not ok 2134 the state roots should match
not ok 2161 the state roots should match

[axic]

So apparently this one is the correct behaviour as per the sidenote in the YP in section H.1.

[jwasinger]

Working on this. I was able to bring failures down from 569->526.

[jwasinger]

Down to 2 failures!

[axic]

@jwasinger can you let me know when this is near completion? I'd like to squash done some commits (mostly mine).

[jwasinger]

@axic Sure. I'm working on the remaining failures now.

[jwasinger]

@axic I think this is ready (other than linting travis failure).

[jwasinger]

@axic can you squash your commits? then I can fix linting and we can get this merged.

[axic]

Yep will do.

[axic]

Finally this works now, just need to fix lint & squash more things.

[axic]

@jwasinger can you do a review and possibly merge?

[axic]

@jwasinger the funny thing is we had the zeroing out, but the state tests pass with and without so who knows..

[jwasinger]

That's a bit unsettling.. I got hung up on how to remove that hack but I think I've got it now.