When I "cabal configure" on my Ubuntu Intrepid with a virgin GHC 6.10.1 from the
x86_64 binary package, I see no messages. But when I "cabal build", I get:

[134 of 134] Compiling Darcs.RunCommand ( src/Darcs/RunCommand.hs,
dist/build/Darcs/RunCommand.o )                                          

src/hscurl.c:5:23:  error: curl/curl.h: Bestand of map bestaat niet

src/hscurl.c:48:0:
     fout: expected ‘,’ or ‘;’ before ‘LIBCURL_VERSION’

Some more information:

$ ghc-pkg list
/usr/local/lib/ghc-6.10.1/./package.conf:
    Cabal-1.6.0.1, HUnit-1.2.0.3, QuickCheck-1.2.0.0, array-0.2.0.0,
    base-3.0.3.0, base-4.0.0.0, bytestring-0.9.1.4, containers-0.2.0.0,
    directory-1.0.0.2, (dph-base-0.3), (dph-par-0.3),
    (dph-prim-interface-0.3), (dph-prim-par-0.3), (dph-prim-seq-0.3),
    (dph-seq-0.3), editline-0.2.1.0, filepath-1.1.0.1, (ghc-6.10.1),
    ghc-prim-0.1.0.0, haddock-2.3.0, haskell-src-1.0.1.3,
    haskell98-1.0.1.0, hpc-0.5.0.2, html-1.0.1.2, integer-0.1.0.0,
    mtl-1.1.0.2, network-2.2.0.1, old-locale-1.0.0.1, old-time-1.0.0.1,
    packedstring-0.1.0.1, parallel-1.1.0.0, parsec-2.1.0.1,
    pretty-1.0.1.0, process-1.0.1.0, random-1.0.0.1,
    regex-base-0.72.0.2, regex-compat-0.71.0.1, regex-posix-0.72.0.3,
    rts-1.0, stm-2.1.1.2, syb-0.1.0.0, template-haskell-2.3.0.0,
    time-1.1.2.2, unix-2.3.1.0, xhtml-3000.2.0.1

Installing the libcurl-dev distribution package makes it build. The problem is
that darcs does not fail during configure and gives an unclear message when it
fails during build.

It appears that the feature of checking for C libraries and/or headers at
configure time was added to Cabal a few weeks ago:
http://hackage.haskell.org/trac/hackage/ticket/262 .

The following patch updated the status of issue1361 to be resolved:

* resolve issue1361: specify required includes for curl in cabal file 
Ignore-this: 2581d04c7534d750575dd4732911fb8f