I would start by reading and experimenting with the source.   In my opinion,  cabal and cabal-install are not exactly elegant programs,  but if you are only interested in a few isolated issues,  they aren&#39;t too hard to reverse-engineer with a little determination and patience.<div>
<br></div><div>Oftentimes you know what commands and arguments you wish to run in some specific case,  but you don&#39;t know how to properly construct these paths and flags and whatnot in generic cabal settings.  I&#39;ve found it easiest to modify the source to print the data structures out and examine them for the information you are seeking.  The &quot;groom&quot; package is very helpful in this regard,  as it can pretty print these structures for you.   You can then examine the source to find out how the fields you are interested in are set and consumed;  usually the control flow is fairly simple in this regard.    Admittedly it seems like some kind of code smell to have such large records with the vast majority of fields only used in a handful of locations,  but it also makes for relatively simple reverse engineering with modest tools.</div>
<div><br></div><div>Cabal is somewhat easier to work with in this regard than cabal-install,  because you can just get access to most of the datastructures you want via callbacks in Setup.hs.   And since they derive Show instances,  you can use groom.    Unfortunately most of the datatypes that cabal-install uses didn&#39;t derive Show instances,  at least the last time I checked,  but that&#39;s also easy to fix.</div>
<div><br></div><div>Maybe somebody else could offer better, more specific advice.   I&#39;ve only toyed with little bits of Cabal hacking,  and most of the time I didn&#39;t feel like the results were worth sharing.   The only bit that I have shared so far would be this,  which uses the postHaddock hook to copy a png into the documentation directory:</div>
<div><br></div><div><a href="https://github.com/lpsmith/split-channel/commit/2edf5c652ef642579919a18531bd3a8ad8cf7cee">https://github.com/lpsmith/split-channel/commit/2edf5c652ef642579919a18531bd3a8ad8cf7cee</a></div><div>
<br></div><div>However I hear rumors that future versions of Cabal might support this particular use case natively. </div><div><br></div><div>Best,</div><div>Leon<br><div><br></div><div><br><div class="gmail_quote">On Fri, Feb 22, 2013 at 2:33 AM, Edwin <span dir="ltr">&lt;<a href="mailto:edwinhere@gmail.com" target="_blank">edwinhere@gmail.com</a>&gt;</span> wrote:<br>
<blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><div dir="ltr">Hi,<div><br></div><div>I am a newbie to Haskell, and I want to try to add DLL creation support to Cabal.</div>
<div><br></div><div>Where do I start?</div><div><br></div><div>I have already made a DLL using ghc and and .bat files for use in trading. But the process is a bit tedious. The IRC people said, I should try to add DLL support into Cabal.</div>
<span class="HOEnZb"><font color="#888888">
<div><br></div><div>Edwin</div></font></span></div>
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