The 7.2.2 release is a bugfix release. The changes relative to 7.2.1 are listed below. The 7.2 branch is intended to be more of a "technology preview" than normal GHC stable branches.
All packages are now trusted by default. If you wish to make use of Safe Haskell, you will need to manually untrust packages that you do not wish to trust.
An optimiser bug (#5453) which can cause segfaults has been fixed.
A native code generator bug (#5393) which can cause segfaults on x86 and amd64 has been fixed.
A race condition in the runtime system (#5552) that can cause segfaults has been fixed.
Exception handlers are now run in the mask
state, rather than the maskUninterruptible
state. Fixes a bug that could cause the GHCi debugger to hang
(#4988),
amongst other things.
The shutdownHaskellAndExit function now
immediately exits, even if hs_init has
been called multiple times.
A bug arising when using type signature declarations in Template Haskell splices (#5404) has been fixed.
A bug arising when using class instances in Template Haskell splices (#5410) has been fixed.
Incorrectly encoded text at the end of a file is now handled correctly (#5436).
The base package is now version 4.4.1.0 (was 4.4.0.0).
Haddock is now version 2.9.4.