6.4.2 is a bugfix release over 6.4.1. Most library APIs have not changed, so code that worked with 6.4.1 should continue to work with 6.4.2. The main exception is that the Cabal library has been updated, so code using the old Cabal may need to be modified.
Many, many bugs have been fixed relative to 6.4.1. Far too many to list here.
6.4.2 now works correctly with gcc 4.x; if you are using gcc 4.x, then you need 6.4.2.
This is the last GHC release from the CVS repository. Future releases will be made from a darcs repository.
The following new features were added in this release:
Cabal has been upgraded to version 1.1.4. While strictly speaking this breaks our rules about not changing any library APIs in a patchlevel release, it was felt that the Cabal shipped in 6.4.1 was lacking in various important ways, and it was more important to provide a Cabal that works with more existing packages. Some distributions of GHC were already supplying an upgraded Cabal by default.
The environment variable GHC_PACKAGE_PATH can be
set to a list of package databses for GHC to use in addition to (or
optionally instead of) the default databases. See Section 4.8.3.1, “The GHC_PACKAGE_PATH environment variable”.
Some minor changes to the command line syntax of the
ghc-pkg command, in particular the handling of the
--user, --global and
--package-conf (-f) options has been
cleaned up. See Section 4.8.5, “Package management (the ghc-pkg command)”.
On x86-64 machines, FFI calls can be used from interpreted code in GHCi (support for this was previously missing).
A new GHCi command: :set prompt. See Section 3.6, “GHCi commands”.
There is a new field in InstalledPackageInfo: extraGHCiLibraries, for use when you want to load different libraries for a package when running under GHCi.
The FAQ is no longer part of the User's Guide, it is now on the wiki.
Retainer and biographical heap profiling now works with STM (previously it didn't).
GHCi is now linked with the threaded RTS. This means that other
threads will not stop running just because GHCi is waiting at the
prompt, and things like waitForProcess work
without blocking other threads.
The OpenAL library has been updated to the latest version, to work around build problems on some platforms.