Completely reproducible Haskell builds
marlowsd at gmail.com
Fri May 27 17:35:17 CEST 2011
On 26/05/2011 17:15, Greg Steuck wrote:
> I am trying to get ghc-7.0.3 build procedure down to a byte-identical
> rebuild on Linux-amd64.
This is likely to be very fragile with GHC at the moment, due to some
non-deterministic behaviour in its internals. I have tried to eliminate
as much as I can, but there are still a couple of known sources, and
possibly more unknown ones. See the last bullet point here:
Having said that I think it's a good idea to fix any sources of binary
differences as you're doing.
> The best option for dealing with this seems to be using gcc ability to
> accept input from a pipe. I know I could make this work on a Posix
> system. Yet I suspect getting it to work on Windows would be overly
> Next best idea is to make GHC use repeatable temporary .c& .o file
> names for each invocation. There is already a unique temporary
> directory where all the the temporary files are created. This suggests
> I do not need to worry about adversarial races. So GHC just need to
> avoid racing with itself. I see a couple of options:
> 1) newTempName should create a new subdirectory for each call and
> the return a fixed name inside of this (so /tmp/ghc28016_0/ghc28016_0.c
> above would become /tmp/ghc28016_0/0/dummy.c)
> 2) mkExtraCObj could compute some hash function of its xs
> argument (C program text) and then create a file named, e.g.
> Which of these two looks better? Other ideas?
The first is easier, and would be fine with me.
> Would people be open to accepting a patch along these lines if I were
> to write one?
Sure. But as I mentioned above, this might not be enough, or at least
you might still get random differences from time to time.
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