ExitFailure 9 when trying to install ghc-mod using Cabal

Question

When I try to install it with cabal, I get

~$ cabal install ghc-mod
Resolving dependencies...
[1 of 1] Compiling Main             ( /tmp/haskell-src-exts-1.13.5-21238/haskell-src-exts-1.13.5/Setup.hs, /tmp/haskell-src-exts-1.13.5-21238/haskell-src-exts-1.13.5/dist/setup/Main.o )

/tmp/haskell-src-exts-1.13.5-21238/haskell-src-exts-1.13.5/Setup.hs:1:1:
    Warning: In the use of `runTests'
             (imported from Distribution.Simple, but defined in Distribution.Simple.UserHooks):
             Deprecated: "Please use the new testing interface instead!"
Linking /tmp/haskell-src-exts-1.13.5-21238/haskell-src-exts-1.13.5/dist/setup/setup ...
Configuring haskell-src-exts-1.13.5...
Building haskell-src-exts-1.13.5...
Preprocessing library haskell-src-exts-1.13.5...

dist/build/Language/Haskell/Exts/InternalParser.hs:1:12:
    Warning: -fglasgow-exts is deprecated: Use individual extensions instead
[ 1 of 22] Compiling Language.Haskell.Exts.Annotated.Syntax ( src/Language/Haskell/Exts/Annotated/Syntax.hs, dist/build/Language/Haskell/Exts/Annotated/Syntax.o )
cabal: Error: some packages failed to install:
ghc-mod-1.11.1 depends on haskell-src-exts-1.13.5 which failed to install.
haskell-src-exts-1.13.5 failed during the building phase. The exception was:
ExitFailure 9
hlint-1.8.33 depends on haskell-src-exts-1.13.5 which failed to install.

I'm not really sure where to go from here. How can I find out more about why it failed?

edit: I'm using GHC version 7.4.1 and Cabal version 1.14.0

Running Cabal in verbose mode doesn't seem to give any hints except:

...

World file is already up to date.
cabal: Error: some packages failed to install:
ghc-mod-1.11.1 depends on haskell-src-exts-1.13.5 which failed to install.
haskell-src-exts-1.13.5 failed during the building phase. The exception was:
ExitFailure 9
hlint-1.8.33 depends on haskell-src-exts-1.13.5 which failed to install.

Answer 1

It turned out to be a running-out-of-memory issue, as hammar suspected. I was able to get it to install (although it was painfully slow) by adding a 1GB swap file to the system:

dd if=/dev/zero of=/swapfile bs=1M count=1024
mkswap /swapfile
swapon /swapfile

Apparently EC2 instances come without swap by default.