Hmm, I've never heard of linking being a bottleneck. Even GHC itself links in about 3-4 seconds here. One common problem is that linking on a network filesystem takes a *lot* longer than linking objects from a local disk. It's always a good idea to keep the build tree on the local disk, even if the sources are NFS-mounted.

Unfortunately, we're not talking seconds, but coffee-breaks of linking times on our Sun (yes, the stuff is in the range of a large compiler - we're fortunate enough to be able to build on rather substantial third-party packages, think haskell-in-haskell frontend distributed over unusually many modules + strategic traversal support + our own code). And yes, I was worried about NFS-mounting first, especially since linking on our Sun takes even longer than on our PCs (long breaks instead of short ones;-), but moving .hi and .o to local tmp-space didn't speed things up (then again, it's a large machine, and our disk setup is likely to be more complex than I know - I'll have to check with our admins).

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Alternative a: use someone else's incremental linker, e.g., Sun's ild (ghc's -pgml option appears to have its own idea about option formatting, btw) - this doesn't seem to work - should it?

You'd probably want to call the incremental linker directly rather than using GHC - what exactly does it do, BTW? What files does it generate?

Calling it via GHC seemed the best way to ensure that it gets everything it needs (what else would be the purpose of -pgml?). According to docs, ild just keeps more information and space in the linked object, so that on re-linking, it can (a) check for file-modification times and (b) replace and partially relink only those contributing objects that have changed. http://docs.sun.com/db/doc/802-5693/6i9edqka5?l=zh&a=view

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Alternative b: convince ghc to link objects in stages, e.g., on a per-directory basis - gnu's ld seems to support at least this kind of partial linking (-i/-r). Not quite as nice as a fully incremental linker, but would probably save our day..

Yes, this works fine. We use it to build the libraries for GHCi.

Presumably directed via Makefiles? Could this please be automated for ghc --make? Thanks, Claus