Hi Ben,

this is great news! I'm particularly keen on learning more about two points you mentioned in your email:

* Compiler performance: do you have any numbers to quantify what 8.0 vs 8.2 is likely to look like? How much has the work that's been done affect performance across the board? Or are these mostly pathological cases (e.g. ghc --make with high number of cores, large number of definitions in a module, large amount of let nesting in definitions, etc)
* DWARF support: could you clarify at a very high-level what typical uses cases can be expected to work and which ones won't? Would be eager to read any resources you could point me at to help me understand what still needs to be done on this front.

Many thanks,

--
Mathieu Boespflug
Founder at http://tweag.io.

On 10 April 2017 at 05:50, Ben Gamari <ben@well-typed.com> wrote:

Hello everyone,

The GHC team is very pleased to announce the first candidate of the
8.2.1 release of the Glasgow Haskell Compiler. Source and binary
distributions are available at

    https://downloads.haskell.org/~ghc/8.2.1-rc1/

This is the first of a few release candidates leading up the final 8.2.1
release. This release will feature,

  * A new type-indexed Typeable implementation

  * The long awaited Backpack

  * Deriving strategies for disambiguating DeriveAnyClass,
    GeneralizedNewtypeDeriving, and stock mechanisms

  * Overloaded record fields

  * Improved compiler performance

  * Better code generation through more robust tracking of join points

  * Compact regions for more efficient garbage collection and serialization

  * Better support for machines with non-uniform memory architectures

  * More robust support for levity (e.g. RuntimeRep) polymorphism

  * A simple interface for streaming eventlog data from live processes

  * Further refinement of DWARF support

Unfortunately there are still a few known issues in this release,
including a few compiler panics (#13233, #13509) and a memory leak in
the simplifier (#13426) which may adversely affect heap sizes and
compilation time for some modules. This memory leak unfortunately made
it impossible to provide a 32-bit Windows distribution for this
candidate; this will be resolved in -rc2.

As always, please let us know if you have difficulty. Thanks to everyone
who has contributed to this release!

Happy testing,

- Ben


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