#179: support GHC's main-is extension
----------------------------+-----------------------------------------------
Reporter: duncan | Owner:
Type: enhancement | Status: reopened
Priority: low | Milestone: _|_
Component: Cabal library | Version: 1.2.2.0
Severity: normal | Resolution:
Keywords: | Difficulty: normal
Ghcversion: 6.4.2 | Platform: Linux
----------------------------+-----------------------------------------------
Comment(by cjs):
Ah, sorry. Basically, different and incompatible object files are produced
when you compile the same source with and without --main-is. Any object
files compiled with --main-is cannot be linked into another program (that
has its own main) because the two main functions will conflict at the link
stage. Basically, the link stage doesn't know from main, it just links all
the stuff together and depends on one (and only one) object file to have a
program entry point (a "main") of some sort specified.
This is a bit insidious because the object files go to the same location
when compiled with or without --main-is. So if you do a clean build of
some system with your --main-is set to one module, you will successfully
link your final program. If you re-compile with the --main-is option
reset, the GHC dependency checker (--make option) does not know that
another module was previously compiled with --main-is, and when you hit
the link stage you will get an error.
Well, this is more or less how I remember it. If this still doesn't make
sense, it's probably best to contact me via e-mail (c...@cynic.net) and I
can put together an example that demonstrates the problem more precisely,
and give suggestions on how to have the build system deal with the issue
(essentially, putting any object files compiled with --main-is in a
separate object directory or just giving them different names).
--
Ticket URL: <http://hackage.haskell.org/trac/hackage/ticket/179#comment:23>
Hackage <http://haskell.org/cabal/>
Hackage: Cabal and related projects
_______________________________________________
cabal-devel mailing list
cabal-devel@haskell.org
http://www.haskell.org/mailman/listinfo/cabal-devel
