Some while ago, they added a feature to the Haskell compiler where you 
can link Haskell libraries dynamically rather than statically.

However, this feature works only on Unix, because Haskell hates Windows.

*sigh*


But wait! What's this? The latest and greatest version of GHC just 
released now supports Windows DLLs too. Cool!

...well, partly cool anyway.

Good things:

- Compiling the Hello World program with static libraries gives me a 
518KB file, but with dynamic libraries that goes down to 13KB.

Bad things:

- The program doesn't actually /run/ any more. It can't find the 
necessary DLLs. It seems that /you/ have to manually copy them to 
somewhere sensible and/or alter the search path.

- Finding the DLL files is non-trivial. Rather than putting them all in 
one folder, the installer scatters them across the filesystem in a 
pseudo-random manner. (This is quite probably why the DLL loader can't 
find them either.)

- Hello World requires the DLLs for the Haskell run-time system, Haskell 
compiler primitives, foreign function interface, arbitrary-precision 
integers, and of course the Haskell "base" library. That's 5 DLLs you 
have to have in your search path.

- These five DLLs add up to 8MB. (!)

03/12/2010  03:55 PM            12,814 HelloWorld.exe
13/11/2010  12:16 AM         7,015,961 libHSbase-4.3.0.0-ghc7.0.1.dll
13/11/2010  12:18 AM            35,854 libHSffi-ghc7.0.1.dll
13/11/2010  12:16 AM           676,886 libHSghc-prim-0.2.0.0-ghc7.0.1.dll
13/11/2010  12:16 AM           394,520 libHSinteger-gmp-0.2.0.2-ghc7.0.1.dll
13/11/2010  12:18 AM           266,240 libHSrts-ghc7.0.1.dll
                6 File(s)      8,402,275 bytes

And you thought MSVBVM50.DLL was a pain! >_<

(I especially love the way that I'm not actually /using/ FFI or 
arbitrary-precision integers, and yet I must have the DLLs installed. 
But then, *I* am not using FFI, but the entire Haskell I/O system is 
based on it. Similarly, file sizes are returned as arbitrary-precision 
integers, so the DLL for that is required.)

In summary, I don't think I'll rush out and use this feature anytime soon.



Also entertaining is the way that several new features of the compiler 
aren't accurately reflected in all of the documentation. (E.g., some 
chapters claim that shared libraries don't work on Windows, while others 
assert that they do...)

PS. I just tried compiling with dynamic libraries using an older version 
of the compiler (i.e., one which supports it on Unix but not on 
Windows). Rather than saying "sorry, this is not supported on Windows", 
or even just "unrecognised flag name", instead it crashes with a 
file-not-found error from GCC. Graceful failure, anyone?

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