[OE-core] [RFC][PATCH 2/2] buildhistory: support generating md5sum of files

[Jacob Kroon]

Hi Richard,

On Mon, Jan 7, 2019 at 3:31 PM Richard Purdie
<richard.purdie at linuxfoundation.org> wrote:
>
> On Mon, 2019-01-07 at 10:38 +0100, Jacob Kroon wrote:
> > On Mon, Jan 7, 2019 at 12:09 AM André Draszik <git at andred.net> wrote:
> > > I don't know what the intended use-case of the md5 files is, but
> > > could
> > > sha256 or similar maybe be more appropriate?
> >
> > I thought it would be a good idea to store some sort of checksum of
> > files in the
> > buildhistory when doing reproducible builds, so that it is easier to
> > detect
> > when a rebuild produces changed files, but perhaps there is some way
> > to do
> > this already that I am missing ?
> >
> > But I have no real motivation for choosing md5, other than that I
> > assumed it would be less
> > cpu intensive than sha256, and the fact I'm not too worried about
> > collisions.
>
> I used to lean that way as well however there is a fair bit of
> negativity associated with *any* use of md5 so I'm tempted to say use
> sha256 as we don't know how these checksums may be used in the future.

Ok.

> I'd note there is some overlap here with the sstate hash equivalency
> work where we build a hash representing a tasks complete output. Can
> you reuse any of the functions there?

I'll look into it, I realize it would of course be nice if we only
needed to calculate the checksums once.

Thanks for the feedback,
Jacob

> Cheers,
>
> Richard
>