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ICU-9648 Added a note in What's new section in readme.html about the subclassing-API breaking change in BasicTimeZone.

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Yoshito Umaoka 2013-02-05 22:16:11 +00:00
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icu4c/readme.html
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@ -3,9 +3,9 @@
<html lang="en-US" xmlns="http://www.w3.org/1999/xhtml" xml:lang="en-US">
<head>
<title>ReadMe for ICU 50</title>
<title>ReadMe for ICU 51</title>
<meta name="COPYRIGHT" content=
"Copyright (c) 1997-2012 IBM Corporation and others. All Rights Reserved." />
"Copyright (c) 1997-2013 IBM Corporation and others. All Rights Reserved." />
<meta name="KEYWORDS" content=
"ICU; International Components for Unicode; ICU4C; what's new; readme; read me; introduction; downloads; downloading; building; installation;" />
<meta name="DESCRIPTION" content=
@ -16,7 +16,7 @@
<body class="draft">
<h1>International Components for Unicode<br />
<abbr title="International Components for Unicode">ICU</abbr> 50 (Release Candidate) ReadMe</h1>
<abbr title="International Components for Unicode">ICU</abbr> 51 (Release Candidate) ReadMe</h1>
<!--<p><b>Note:</b> This is a development milestone release of ICU4C 50.
This milestone is intended for those wishing to get an early look at ICU 50 new features and API changes.
@ -24,8 +24,8 @@
<!--<p><b>Note:</b> This is a release candidate version of ICU4C 50.
It is not recommended for production use.</p>-->
<p>Last updated: 2012-Oct-31<br />
Copyright &copy; 1997-2012 International Business Machines Corporation and
<p>Last updated: 2013-Feb-5<br />
Copyright &copy; 1997-2013 International Business Machines Corporation and
others. All Rights Reserved.</p>
<!-- Remember that there is a copyright at the end too -->
<hr />
@ -224,55 +224,21 @@
<a href="http://site.icu-project.org/download/milestone">ICU milestone download page</a>.
</p>
<h3>Thread safety support cannot be removed</h3>
<p>ICU4C 50 dropped support for the --enable-threads/--disable-threads configure option
and the uconfig.h <code>ICU_USE_THREADS</code> switch.
ICU4C 50 and higher is always built with multi-threading safety support.
ICU4C has never created threads in its libraries.</p>
<h3>C++ BasicTimeZone subclassing-API breaking changes</h3>
<p>We have made make some changes to the C++ BasicTimeZone(basictz.h) for ICU 51
that will make it easier to use some time zone support features found in BasicTimeZone
(basictz.h), but the changes are incompatible for subclasses. If there are subclasses,
they will have to be modified as well.</p>
<p>If you need to prevent ICU from using thread safe mutexes when your application does
not create threads, then you can use the --enable-weak-threads configure option.
The --enable-weak-threads configure option will cause ICU to weakly reference the
pthread mutex functions, and the stub implementations in the C runtime will be used.
If this configure option does not work on your platform, then you can call
<code>u_setMutexFunctions()</code> and <code>u_setAtomicIncDecFunctions()</code>
with your own empty implementations.</p>
<p>BasicTimeZone is a subclass of TimeZone and providing some enhanced features, such as
getNextTransition and getPreviousTransition. The class is used as the base class of all
of ICU's time zone implementation classes. User Classes directly extending TimeZone and
consumers of ICU TimeZone implementation classes are not affected by the changes.</p>
<h3>The default compilers have changed</h3>
<p>ICU has changed the compilers chosen by default. If the clang and clang++ compilers
are available, those will be used instead of gcc and g++. If the clang compilers
are not available, then gcc and g++ will be used just as before. The clang++ compiler
provides C++11 support and some optimizations that are helpful to ICU. The API
remains the same between these two sets of compilers, but ICU can internally leverage
language features and optimizations that are available in clang++.</p>
<p>If you need to force ICU to compile with gcc and g++, then you can use the following
from the command line in the source directory:</p>
<pre>
<samp>./configure CC=gcc CXX=g++ CFLAGS=-O3 CXXFLAGS=-O3</samp>
</pre>
<h3>C++ Collator subclassing-API breaking changes</h3>
<p>We have made some changes to the C++ Collator API for ICU 50
that will make it easier to use and implement the Collator but
which are incompatible for subclasses.
If there are subclasses, they will have to be modified as well.
It will be easy to adapt subclass source code, if there is any.
We think it is unlikely (or at least rare) that users write subclasses of the C++ Collator,
given the number of virtual methods and the complexities of a collation implementation.</p>
<p>For details see the email "ICU4C C++ Collator subclassing-API breaking changes"
sent on 2012-jul-25 to the icu-design and icu-support
<p>For details see the email "ICU4C C++ BasicTimeZone subclassing-API breaking changes"
sent on 2013-Feb-5 to the icu-support
<a href="http://site.icu-project.org/contacts">mailing lists</a>,
and <a href="http://bugs.icu-project.org/trac/ticket/9346">ICU ticket #9346</a>,
including the <a href="http://bugs.icu-project.org/trac/review/9346">changes for that ticket</a>.</p>
<p>In particular, the <code>class TestCollator</code> in
<a href="http://bugs.icu-project.org/trac/browser/icu/trunk/source/test/intltest/apicoll.cpp"><code>source/test/intltest/apicoll.cpp</code></a>
<a href="http://bugs.icu-project.org/trac/changeset/32100#file5">illustrates how a subclass needs to be changed</a>.
However, note that the TestCollator was also simplified slightly;
not all changes made there were strictly required for the API signature changes.</p>
and <a href="http://bugs.icu-project.org/trac/ticket/9648">ICU ticket #9648</a>.
<h2><a name="Download" href="#Download" id="Download">How To Download the
Source Code</a></h2>