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<?xml version="1.0" encoding="iso-8859-1"?>
<sect1 id="release-7-8-1">
<title>Release notes for version 7.8.1</title>
<para>
The significant changes to the various parts of the compiler are listed
in the following sections. There have also been numerous bug fixes and
performance improvements over the 7.6 branch.
</para>
<sect2>
<title>Highlights</title>
<para>
The highlights, since the 7.6 branch, are:
</para>
<itemizedlist>
<listitem>
<para>
GHC now supports "type holes" with the
<literal>TypeHoles</literal> extension. When enabled, the
unbound literal <literal>_</literal> may be used during
development in place of a regular identifier, and GHC will
respond with the type necessary to "fill in the hole."
TODO FIXME: reference.
</para>
</listitem>
<listitem>
<para>
It is now possible to declare a 'closed' <literal>type
family</literal> when using the
<literal>TypeFamilies</literal> extension. A closed
<literal>type family</literal> cannot have any
instances created other than the ones in its
definition.
TODO FIXME: reference.
</para>
</listitem>
<listitem>
<para>
Use of the <literal>GeneralizedNewtypeDeriving</literal>
extension is now subject to <emphasis>role checking</emphasis>,
to ensure type safety of the derived instances. As this change
increases the type safety of GHC, it is possible that some code
that previously compiled will no longer work.
TODO FIXME: reference.
</para>
</listitem>
<listitem>
<para>
GHC now supports overloading list literals using the new
<literal>OverloadedLists</literal> extension.
TODO FIXME: reference.
</para>
</listitem>
<listitem>
<para>
There has been significant overhaul of the type inference engine and
constraint solver.
TODO FIXME: reference.
</para>
</listitem>
<listitem>
<para>
By default, GHC will now unbox all "small" strict
fields in a data type. A "small" data type is one
whose size is equivalent to or smaller than the native
word size of the machine. This means you no longer
have to specify <literal>UNPACK</literal> pragmas for
e.g. strict <literal>Int</literal> fields. This also
applies to floating-point values.
</para>
</listitem>
<listitem>
<para>
GHC now has a brand-new I/O manager that scales significantly
better for larger workloads compared to the previous one. It
should scale linearly up to approximately 32 cores.
</para>
</listitem>
<listitem>
<para>
The LLVM backend now supports 128bit SIMD operations. This is
now exploited in both the <literal>vector</literal> and
<literal>dph</literal> packages, exposing a high level
interface.
TODO FIXME: reference.
</para>
<para>
This is only available with the LLVM backend.
</para>
</listitem>
<listitem>
<para>
The new code generator, after significant work by many
individuals over the past several years, is now enabled by
default. This is a complete rewrite of the STG to Cmm
transformation. In general, your programs may get slightly
faster.
</para>
<para>
The old code generator has been removed completely.
</para>
</listitem>
<listitem>
<para>
PrimOps for comparing unboxed values now return
<literal>Int#</literal> instead of <literal>Bool</literal>.
New PrimOps' names end with <literal>$#</literal> for operators and
<literal>I#</literal> for ordinary names, e.g. <literal>==$#</literal>
compares <literal>Int#</literal>s for equality and
<literal>eqCharI#</literal> does the same for <literal>Char#</literal>s.
Old PrimOps have been removed and turned into wrappers. If your
code relied on removed PrimOps then importing
<literal>GHC.PrimWrappers</literal> will make it work again (no
need to add anything if your code already imports
<literal>GHC.Exts</literal>).
</para>
</listitem>
<listitem>
<para>
TODO: mention dynamic changes
</para>
</listitem>
<listitem>
<para>
TODO: mention new <literal>Typeable</literal> and
<literal>AutoDeriveTypeable</literal>
</para>
</listitem>
</itemizedlist>
</sect2>
<sect2>
<title>Full details</title>
<sect3>
<title>Language</title>
<itemizedlist>
<listitem>
<para>
There is a new extension,
<literal>NullaryTypeClasses</literal>, which
allows you to declare a type class without any
parameters.
TODO FIXME: example?
</para>
</listitem>
</itemizedlist>
</sect3>
<sect3>
<title>Compiler</title>
<itemizedlist>
<listitem>
<para>
GHC now supports a <literal>--show-options</literal> flag,
which will dump all of the flags it supports to standard out.
</para>
</listitem>
<listitem>
<para>
It's now possible to switch the system linker on Linux
(between GNU gold and GNU ld) at runtime without problem.
</para>
</listitem>
<listitem>
<para>
The <literal>-fwarn-dodgy-imports</literal> flag now warns
in the case an <literal>import</literal> statement hides an
entity which is not exported.
</para>
</listitem>
<listitem>
<para>
The LLVM backend was overhauled and rewritten, and
should hopefully be easier to maintain and work on
in the future.
</para>
</listitem>
</itemizedlist>
</sect3>
<sect3>
<title>GHCi</title>
<itemizedlist>
<listitem>
<para>
GHCi now supports a <literal>prompt2</literal>
setting, which allows you to customize the
continuation prompt of multi-line input.
TODO FIXME: reference.
</para>
</listitem>
</itemizedlist>
</sect3>
<sect3>
<title>Template Haskell</title>
<itemizedlist>
<listitem>
<para>
TODO FIXME
</para>
</listitem>
</itemizedlist>
</sect3>
<sect3>
<title>Runtime system</title>
<itemizedlist>
<listitem>
<para>
The performance of <literal>StablePtr</literal>s and
<literal>StableName</literal>s has been improved.
</para>
</listitem>
</itemizedlist>
</sect3>
<sect3>
<title>Build system</title>
<itemizedlist>
<listitem>
<para>
GHC >= 7.4 is now required for bootstrapping.
</para>
</listitem>
<listitem>
<para>
GHC can now be built with Clang, and use Clang as the
preprocessor for Haskell code. Only Clang version 3.4svn is
reliably supported.
</para>
</listitem>
</itemizedlist>
</sect3>
</sect2>
<sect2>
<title>Libraries</title>
<para>
There have been some changes that have effected multiple
libraries:
</para>
<itemizedlist>
<listitem>
<para>
TODO FIXME
</para>
</listitem>
</itemizedlist>
<para>
The following libraries have been removed from the GHC tree:
</para>
<itemizedlist>
<listitem>
<para>TODO FIXME</para>
</listitem>
</itemizedlist>
<para>
The following libraries have been added to the GHC tree:
</para>
<itemizedlist>
<listitem>
<para>TODO FIXME</para>
</listitem>
</itemizedlist>
<sect3>
<title>array</title>
<itemizedlist>
<listitem>
<para>
Version number XXXX (was XXXX)
</para>
</listitem>
</itemizedlist>
</sect3>
<sect3>
<title>base</title>
<itemizedlist>
<listitem>
<para>
Version number 4.7.0.0 (was 4.6.0.1)
</para>
</listitem>
<listitem>
<para>
The <literal>Control.Category</literal> module now has the
<literal>PolyKinds</literal> extension enabled, meaning
that instances of <literal>Category</literal> no longer
need be of kind <literal>* -> * -> *</literal>
</para>
</listitem>
<listitem>
<para>
There are now <literal>Foldable</literal> and <literal>Traversable</literal>
instances for <literal>Either a</literal> and <literal>(,) a</literal>
</para>
</listitem>
<listitem>
<para>
<literal>Control.Concurrent.MVar</literal> has a new
implementation of <literal>readMVar</literal>, which
fixes a long-standing bug where
<literal>readMVar</literal> is only atomic if there
are no other threads running
<literal>putMVar</literal>.
<literal>readMVar</literal> now is atomic, and is
guaranteed to return the value from the first
<literal>putMVar</literal>. There is also a new <literal>tryReadMVar</literal>
which is a non-blocking version.
</para>
</listitem>
<listitem>
<para>
There are now byte endian-swapping primitives
available in <literal>Data.Word</literal>, which
use optimized machine instructions when available.
</para>
</listitem>
</itemizedlist>
</sect3>
<sect3>
<title>bin-package-db</title>
<itemizedlist>
<listitem>
<para>
This is an internal package, and should not be used.
</para>
</listitem>
</itemizedlist>
</sect3>
<sect3>
<title>binary</title>
<itemizedlist>
<listitem>
<para>
Version number XXXX (was XXXX)
</para>
</listitem>
</itemizedlist>
</sect3>
<sect3>
<title>bytestring</title>
<itemizedlist>
<listitem>
<para>
Version number XXXX (was XXXX)
</para>
</listitem>
</itemizedlist>
</sect3>
<sect3>
<title>Cabal</title>
<itemizedlist>
<listitem>
<para>
Version number XXXX (was XXXX)
</para>
</listitem>
</itemizedlist>
</sect3>
<sect3>
<title>containers</title>
<itemizedlist>
<listitem>
<para>
Version number XXXX (was XXXX)
</para>
</listitem>
</itemizedlist>
</sect3>
<sect3>
<title>deepseq</title>
<itemizedlist>
<listitem>
<para>
Version number XXXX (was XXXX)
</para>
</listitem>
</itemizedlist>
</sect3>
<sect3>
<title>directory</title>
<itemizedlist>
<listitem>
<para>
Version number XXXX (was XXXX)
</para>
</listitem>
</itemizedlist>
</sect3>
<sect3>
<title>filepath</title>
<itemizedlist>
<listitem>
<para>
Version number XXXX (was XXXX)
</para>
</listitem>
</itemizedlist>
</sect3>
<sect3>
<title>ghc-prim</title>
<itemizedlist>
<listitem>
<para>
Version number XXXX (was XXXX)
</para>
</listitem>
</itemizedlist>
</sect3>
<sect3>
<title>haskell98</title>
<itemizedlist>
<listitem>
<para>
Version number XXXX (was XXXX)
</para>
</listitem>
</itemizedlist>
</sect3>
<sect3>
<title>haskell2010</title>
<itemizedlist>
<listitem>
<para>
Version number XXXX (was XXXX)
</para>
</listitem>
</itemizedlist>
</sect3>
<sect3>
<title>hoopl</title>
<itemizedlist>
<listitem>
<para>
Version number XXXX (was XXXX)
</para>
</listitem>
</itemizedlist>
</sect3>
<sect3>
<title>hpc</title>
<itemizedlist>
<listitem>
<para>
Version number XXXX (was XXXX)
</para>
</listitem>
</itemizedlist>
</sect3>
<sect3>
<title>integer-gmp</title>
<itemizedlist>
<listitem>
<para>
Version number XXXX (was XXXX)
</para>
</listitem>
</itemizedlist>
</sect3>
<sect3>
<title>old-locale</title>
<itemizedlist>
<listitem>
<para>
Version number XXXX (was XXXX)
</para>
</listitem>
</itemizedlist>
</sect3>
<sect3>
<title>old-time</title>
<itemizedlist>
<listitem>
<para>
Version number XXXX (was XXXX)
</para>
</listitem>
</itemizedlist>
</sect3>
<sect3>
<title>process</title>
<itemizedlist>
<listitem>
<para>
Version number XXXX (was XXXX)
</para>
</listitem>
</itemizedlist>
</sect3>
<sect3>
<title>template-haskell</title>
<itemizedlist>
<listitem>
<para>
Version number XXXX (was XXXX)
</para>
</listitem>
</itemizedlist>
</sect3>
<sect3>
<title>time</title>
<itemizedlist>
<listitem>
<para>
Version number XXXX (was XXXX)
</para>
</listitem>
</itemizedlist>
</sect3>
<sect3>
<title>unix</title>
<itemizedlist>
<listitem>
<para>
Version number 2.7.0.0 (was 2.6.0.0)
</para>
</listitem>
<listitem>
<para>
A crash in <literal>getGroupEntryForID</literal>
(and related functions like
<literal>getUserEntryForID</literal> and
<literal>getUserEntryForName</literal>) in
multi-threaded applications has been fixed.
</para>
</listitem>
<listitem>
<para>
The functions <literal>getGroupEntryForID</literal>
and <literal>getUserEntryForID</literal> now fail
with a <literal>isDoesNotExist</literal> error when
the specified ID cannot be found.
</para>
</listitem>
</itemizedlist>
</sect3>
<sect3>
<title>Win32</title>
<itemizedlist>
<listitem>
<para>
Version number XXXX (was XXXX)
</para>
</listitem>
</itemizedlist>
</sect3>
</sect2>
</sect1>
|
