More failure

[Phyx]

Hi Andrey,

I'm not sure what the original issue here is (should probably find the
original message) but

> The Make build system happens to do the right thing, somehow. I believe
we should be able to express the same logic in Shake, but it's not easy.

I believe this typically works because GCC and GHC support dumping the
dependencies that a command would have caused to a file. So your dynamic
dependencies don't matter as their static to the build system after this
invocation.

See
https://downloads.haskell.org/~ghc/latest/docs/html/users_guide/separate_compilation.html#dependency-generation

These Compilers are able to dump out make rules which enabled better
dependency handling..

Kind regards,
Tamar

Sent from my Mobile

On Tue, Dec 10, 2019, 00:58 Andrey Mokhov <andrey.mokhov at newcastle.ac.uk>
wrote:

> Hi Simon,
>
>
>
> (Re-sending from the email address that’s allowed on the mailing list.)
>
>
>
> > Ugh.  That's not a very happy state of affairs, is it?  It didn't happen
> with 'make'.
>
> > Is it a fundamental problem, or just not yet fixed?
>
>
>
> I think this is not a fundamental problem, but the problem of getting
> dependencies right.
>
>
>
> In this case, the complexity comes from the fact that a single invocation
> of GHC produces a set of files, and which set depends on the command line
> flags, which are in turn determined dynamically by reading environment
> settings (specifically, `platformSupportsSharedLibs`).
>
>
>
> Such rules are hard to describe precisely, because build systems are tuned
> to the typical case where we statically know, for every output file, which
> rule produces it -- recall the Tasks = k -> Maybe Task function from our
> paper. In this case, we deal with something like k -> f (Maybe Task)
> instead, i.e. with `f` around the Maybe.
>
>
>
> The Make build system happens to do the right thing, somehow. I believe we
> should be able to express the same logic in Shake, but it's not easy.
>
>
>
> (I never really had a chance to look at dynamic builds, since they are not
> supported on Windows. I guess I should finally find a Linux box for
> Hadrian.)
>
>
>
> Cheers,
>
> Andrey
> _______________________________________________
> ghc-devs mailing list
> ghc-devs at haskell.org
> http://mail.haskell.org/cgi-bin/mailman/listinfo/ghc-devs
>
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