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_com...
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
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@haskell.org http://mail.haskell.org/cgi-bin/mailman/listinfo/ghc-devs