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3<title>Clang 3.0 Release Notes</title>
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16<div id="content">
17
18<h1>Clang 3.0 Release Notes</h1>
19
20<img align=right src="http://llvm.org/img/DragonSmall.png"
21 width="136" height="136" alt="LLVM Dragon Logo">
22
23<ul>
24 <li><a href="#intro">Introduction</a></li>
25 <li><a href="#whatsnew">What's New in Clang 3.0?</a>
26 <ul>
27 <li><a href="#majorfeatures">Major New Features</a></li>
28 <li><a href="#cchanges">C Language Changes</a></li>
29 <li><a href="#cxxhanges">C++ Language Changes</a></li>
30 <li><a href="#objchanges">Objective-C Language Changes</a></li>
31 <li><a href="#apichanges">Internal API Changes</a></li>
Richard Smith855746b2011-11-28 20:02:05 +0000[diff] [blame]32 </ul>
Chandler Carruthc00c0c32011-11-28 07:16:19 +0000[diff] [blame]33 </li>
34 <li><a href="#knownproblems">Known Problems</a></li>
35 <li><a href="#additionalinfo">Additional Information</a></li>
36</ul>
37
38<div class="doc_author">
39 <p>Written by the <a href="http://llvm.org/">LLVM Team</a></p>
40</div>
41
42<!--
43<h1 style="color:red">These are in-progress notes for the upcoming LLVM 3.0
44release.<br>
45You may prefer the
46<a href="http://llvm.org/releases/2.9/docs/ReleaseNotes.html">LLVM 2.9
47Release Notes</a>.</h1>
48 -->
49
50<!-- ======================================================================= -->
51<h2 id="intro">Introduction</h2>
52<!-- ======================================================================= -->
53
54<p>This document contains the release notes for the Clang C/C++/Objective-C
55frontend, part of the LLVM Compiler Infrastructure, release 3.0. Here we
56describe the status of Clang in some detail, including major improvements from
57the previous release and new feature work. For the general LLVM release notes,
58see <a href ="http;//llvm.org/docs/ReleaseNotes.html">the LLVM
59 documentation</a>. All LLVM releases may be downloaded from the
60<a href="http://llvm.org/releases/">LLVM releases web site</a>.</p>
61
62<p>For more information about Clang or LLVM, including information about the
63latest release, please check out the main please see the
64<a href="http://clang.llvm.org">Clang Web Site</a> or the
65<a href="http://llvm.org">LLVM Web Site</a>.
66
67<p>Note that if you are reading this file from a Subversion checkout or the main
68Clang web page, this document applies to the <i>next</i> release, not the
69current one. To see the release notes for a specific release, please see the
70<a href="http://llvm.org/releases/">releases page</a>.</p>
71
72<!-- ======================================================================= -->
73<h2 id="whatsnew">What's New in Clang 3.0?</h2>
74<!-- ======================================================================= -->
75
76<p>Some of the major new features and improvements to Clang are listed here.
77Generic improvements to Clang as a whole or two its underlying infrastructure
78are described first, followed by language-specific sections with improvements to
79Clang's support for those languages.</p>
80
81<!-- = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = -->
82<h3 id="majorfeatures">Major New Features</h3>
83<!-- = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = -->
84
Chandler Carrutha3950cc2011-11-28 08:41:06 +0000[diff] [blame]85<h4 id="notes">Unorganized Notes</h4>
86<p>These are completely random notes as I'm organizing my thoughts and reviewing
87the history. Anything still here needs to be distilled and turned into proper
88prose in a section of its own. When doing that, delete the notes.</p>
89<ul>
Chandler Carruth1af40222011-11-28 09:43:30 +0000[diff] [blame]90 <li>Memory reduction -- initializers, macro expansions, source locations,
91 etc.</li>
Chandler Carruth7a1f1482011-11-28 13:02:29 +0000[diff] [blame]92 <li>Major improvements to the interactions between serializing and
93 deserializing the AST and the preprocessor -- argiris</li>
Chandler Carrutha3950cc2011-11-28 08:41:06 +0000[diff] [blame]94</ul>
95
Chandler Carruth58f2cbc2011-11-28 22:34:59 +0000[diff] [blame]96<h4 id="diagnostics">A multitude of improvements to Clang's diagnostics</h4>
97Clang's diagnostics are constantly being improved to catch more issues, explain
98them more clearly, and provide more accurate source information about them.
99A few improvements since the 2.9 release that have a particularly high impact:
100<ul>
101 <li>Substantially shorter messages due to better recovery, fewer include
102 stacks, and tuning verbose features such as 'a.k.a.' type printing.</li>
103 <li>
104 Able to recover and correct from misspelled type names at the begging of statements. For example, Clang now emits:
Richard Smithad5459a2011-11-28 23:16:15 +0000[diff] [blame]105 <pre><b>t.c:6:3: <span class="error">error:</span> use of undeclared identifier 'integer'; did you mean 'Integer'?</b>
Chandler Carruth58f2cbc2011-11-28 22:34:59 +0000[diff] [blame]106 integer *i = 0;
Richard Smithad5459a2011-11-28 23:16:15 +0000[diff] [blame]107 <span class="caret">^~~~~~~</span>
Chandler Carruth58f2cbc2011-11-28 22:34:59 +0000[diff] [blame]108 Integer
Richard Smithad5459a2011-11-28 23:16:15 +0000[diff] [blame]109<b>t.c:1:13: note:</b> 'Integer' declared here
Chandler Carruth58f2cbc2011-11-28 22:34:59 +0000[diff] [blame]110typedef int Integer;
Richard Smithad5459a2011-11-28 23:16:15 +0000[diff] [blame]111 <span class="caret">^</span></pre>
Chandler Carruth58f2cbc2011-11-28 22:34:59 +0000[diff] [blame]112 </li>
113 <li>Expanded typo correction to (among other improvements) look across
114 namespaces and suggest namespace qualifiers in addition to misspellings of the
115 identifier itself.</li>
116 <li>More rich macro expansion backtraces and some (limited) fix-it hints when
117 diagnostics stem from macro arguments.</li>
Chandler Carruth2f376852011-11-28 22:54:33 +0000[diff] [blame]118 <li>Many new warnings have been added to catch common, bug-prone code
119 patterns.</li>
120 <li>Uninitialized values Clang warning was rewritten to be more accurate,
121 faster, and able to differentiate between the <em>possibility</em> of an
122 uninitialized use and the <em>certainty</em> of an uninitialized use.</li>
Chandler Carruth58f2cbc2011-11-28 22:34:59 +0000[diff] [blame]123</ul>
124
Chandler Carruth9a167122011-11-28 22:43:32 +0000[diff] [blame]125<h4 id="libclang">This release saw significant improvements to <code>libclang</code></h4>
126<ul>
127 <li>A broader set of the <code>libclang</code> API is exposed in the Python
128 bindings.</li>
129 <li>Much more of the Clang AST is exposed through <code>libclang</code>'s APIs
130 and cursors.</li>
131 <li>Cursors can now walk more effectively through macros, especially arguments
132 to function-style macros, and resolve to the underlying AST.</li>
133 <li>Improved code completion surrounding macros, macro arguments, and
134 token pasting.</li>
135 <li>Improved code completion for in-class member functions.</li>
136 <li>Crash recovery for <code>libclang</code> clients.</li>
137 <!-- Doug or Ted may want to flesh this out if there are relevant details I'm
138 glossing over... -->
139</ul>
140
Chandler Carruthb882a1d2011-11-28 21:56:30 +0000[diff] [blame]141<h4 id="driver">The Clang GCC-compatible command-line driver improved dramatically</h4>
142A great deal of work went into the GCC-compatible driver for the 3.0 release
143making it support more operating systems, emulate GCC behavior more accurately,
144and support a much broader range of Linux distributions out of the box.
145<ul>
146 <li>More accurate support for hardware architecture pre-defined macros (e.g.,
147 __i686__).</li>
148 <li>Robust library and header search paths for the vast majority of x86 and
149 x86-64 Linux distributions.</li>
150 <li>Improved support for newer Darwin platforms.</li>
151 <li>Partial support for <code>--sysroot=...</code> based cross-compiling on
152 Linux (and similar) host systems.</li>
153 <li>Improved support for locating and using libcxx when installed, especially
154 on Darwin.</li>
155 <!-- There are likely more Darwin-specific improvements to mention here? -->
156 <!-- What support was added for FreeBSD? NetBSD? Anything noteworthy? -->
Chandler Carruth2f376852011-11-28 22:54:33 +0000[diff] [blame]157 <li>Automatic detection of Clang crashes in the driver and preparation of
158 reproduction steps for filing bug reports.</li><!-- Chad, feel free to add
159 more details here. -->
Chandler Carruthb882a1d2011-11-28 21:56:30 +0000[diff] [blame]160</ul>
161
Chandler Carruthc6f2af32011-11-28 19:17:25 +0000[diff] [blame]162<h4 id="ppcallbacks">Expanded support for instrumenting the preprocessor through
163 callbacks</h4>
Chandler Carruthf16d7252011-11-28 21:47:51 +0000[diff] [blame]164Several enhancements were made to the <code>PPCallbacks</code> interface to
165expand the information available to tools and library users of Clang that wish
166to introspect the preprocessing.
Chandler Carruthc6f2af32011-11-28 19:17:25 +0000[diff] [blame]167<ul>
168 <li>The exact text used between the <code>""</code>s or <code>&lt;&gt;</code>s is reported.</li>
169 <li>The header search path used to locate the header is reported.</li>
170 <li>Missing files during including headers reported.</li>
171 <li>The exact source range for expanded macros can be retrieved.</li>
172</ul>
173
Chandler Carruth185e9302011-11-28 23:11:27 +0000[diff] [blame]174<h4 id="windows">Clang is building and tested regularly on Windows and can
175 compile limited subsets of code on Windows</h4>
176Clang is regularly built and tested on a variety of Windows platforms including
177MinGW 32-bit and 64-bit, Cygwin, and natively with MSVC. In addition, Clang can
178be used as a compiler in a few Windows contexts.
179<ul>
180 <li>Normal compilation supported for the MinGW target platform, in both 32-bit
181 and 64-bit, and the Cygwin target platform.</li>
182 <li>Parsing and AST support for Windows Structured Exception Handling.</li>
Francois Pichet551988f2011-11-28 23:30:46 +0000[diff] [blame]183 <li>New -fms-compatibility flag to handle MSVC constructs that could change
184 the meaning of an otherwise well formed program</li>
185 <li>clang can now parse all the MSVC 2010 standard C++ header files
186 in the nominal case, (still need to specifiy -nobuiltininc for some headers).</li>
187 <li>Improved support for MFC code parsing, (still a work in progress).</li>
Francois Pichet0c2198a2011-11-28 23:46:15 +0000[diff] [blame]188 <li>Add support for function template specialization at class scope (-fms-extensions mode).</li>
189 <li>Add support for Microsoft __if_exists/__if_not_exists statements (-fms-extensions mode).</li>
Chandler Carruth185e9302011-11-28 23:11:27 +0000[diff] [blame]190</ul>
191
Chandler Carruth45901b32011-11-29 00:15:26 +0000[diff] [blame^]192<h4 id="availability">New availability attribute to detect and warn about API
193usage across OS X and iOS versions</h4>
194Clang now supports an attribute which documents the availability of an API
195across various platforms and releases, allowing interfaces to include
196information about what OS versions support the relevant features. Based on the
197targeted version of a compile, warnings for deprecated and unavailable
198interfaces will automatically be provided by Clang.
199
200<h4 id="threadsafety">Thread Safety annotations and analysis-based warnings</h4>
201A set of annotations were introduced to Clang to describe the various
202thread-safety concerns of a program, and an accompanying set of analysis based
203warnings will diagnose clearly unsafe code patterns. The annotations are
204described in the
205<a href="http://clang.llvm.org/docs/LanguageExtensions.html#threadsafety">extension specification</a>,
206and the warnings currently supported include:
207<ul>
208 <li>Calling functions without the required locks</li>
209 <li>Reading variables without the required locks</li>
210 <li>Writing to variables without an exclusive lock (even if holding a shared
211 lock)</li>
212 <li>Imbalance between locks and unlocks across loop entries and exits</li>
213 <li>Acquiring or releasing locks out of order</li>
214</ul>
215
216<h4 id="incompleteast">Improved support for partially constructed and/or
217incomplete ASTs</h4>
218For users such as LLDB that are dynamically forming C++ ASTs, sometimes it is
219either necessary or useful to form a partial or incomplete AST. Support for
220these use cases have improved through the introduction of "unknown" types and
221other AST constructs designed specifically for use cases without complete
222information about the C++ construct being formed.
223
Chandler Carrutha0df07d2011-11-28 22:17:58 +0000[diff] [blame]224<!--
225Need Peter and/or Tanya to flesh this out if we want it in 3.0's notes.. The
226state isn't clear just from documentation or commit logs.
227
228<h4 id="opencl">Initial work to support compiling OpenCL with Clang</h4>
229Clang has some (limited) support for compiling OpenCL.
230-->
231
Chandler Carruthc00c0c32011-11-28 07:16:19 +0000[diff] [blame]232<!-- = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = -->
233<h3 id="cchanges">C Language Changes in Clang</h3>
234<!-- = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = -->
235
Richard Smith62d730f2011-11-28 22:48:25 +0000[diff] [blame]236<h4 id="c1xchanges">C1X Feature Support</h4>
237
238<p>Clang 3.0 adds support for the
239<a href="http://clang.llvm.org/docs/LanguageExtensions.html#c1x">
240<code>_Alignas</code>, <code>_Generic</code>, and <code>_Static_assert</code>
241keywords</a>, drafted for inclusion in the next C standard, which is
242provisionally known as C1X. Use <code>-std=c1x</code> or <code>-std=gnu1x</code>
243to enable support for the new language standard. These features are
244backwards-compatible and are available as an extension in all language
245modes.</p>
246
Chandler Carruthc00c0c32011-11-28 07:16:19 +0000[diff] [blame]247<!-- = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = -->
248<h3 id="cxxchanges">C++ Language Changes in Clang</h3>
249<!-- = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = -->
250
Richard Smith855746b2011-11-28 20:02:05 +0000[diff] [blame]251<h4 id="cxx11changes">C++11 Feature Support</h4>
Richard Smith855746b2011-11-28 20:02:05 +0000[diff] [blame]252<p>Clang 3.0 adds support for
253<a href="http://clang.llvm.org/cxx_status.html#cxx11">more of the language
Richard Smith47931382011-11-28 23:35:03 +0000[diff] [blame]254features</a> added in the latest ISO C++ standard,
255<a href="http://www.iso.org/iso/iso_catalogue/catalogue_tc/catalogue_detail.htm?csnumber=50372">C++ 2011</a>.
256Use <code>-std=c++11</code> or <code>-std=gnu++11</code> to enable support for
257these features. The following are now considered to be of production quality:
Richard Smith855746b2011-11-28 20:02:05 +0000[diff] [blame]258<ul>
Chandler Carruthf16d7252011-11-28 21:47:51 +0000[diff] [blame]259 <li>Range-based <code>for</code> loops</li>
260 <li>Alias declarations (a new syntax for <code>typedef</code> declarations),
261 including their <code>template</code> forms</li>
Richard Smith855746b2011-11-28 20:02:05 +0000[diff] [blame]262 <li>Specifying default values for class data members within a class
263 definition</li>
264 <li>Constructors delegating to other constructors of the same class</li>
Chandler Carruthf16d7252011-11-28 21:47:51 +0000[diff] [blame]265 <li>The <code>override</code> context-sensitive keyword for virtual member
Richard Smith855746b2011-11-28 20:02:05 +0000[diff] [blame]266 function declarations</li>
Chandler Carruthf16d7252011-11-28 21:47:51 +0000[diff] [blame]267 <li>Explicitly generating default function definitions with
268 <code>= default</code></li>
269 <li>The <code>nullptr</code> keyword, and the corresponding type</li>
Richard Smith855746b2011-11-28 20:02:05 +0000[diff] [blame]270 <li>Raw string literals with arbitary delimiters (for instance,
Chandler Carruthf16d7252011-11-28 21:47:51 +0000[diff] [blame]271 <code>R"delim(str"ing)delim"</code>)</li>
272 <li>Unicode string literals (for instance, <code>U"\u1234"</code>) and the
273 <code>char16_t</code> and <code>char32_t</code> built-in types
274 <li><code>noexcept</code> expressions and the <code>noexcept</code> specifier
275 on function declarations</li>
276 <li><code>alignof</code> expressions and the <code>alignas</code> specifier on
Richard Smith855746b2011-11-28 20:02:05 +0000[diff] [blame]277 variable declarations</li>
278 <li>A full set of <a href="http://clang.llvm.org/docs/LanguageExtensions.html#checking_type_traits">type traits</a>,
279 sufficient to support C++11 standard libraries</li>
280</ul>
Chandler Carruthbc02a042011-11-28 21:55:34 +0000[diff] [blame]281All warning and language selection flags which previously accepted
282<code>c++0x</code> now accept <code>c++11</code>. The old <code>c++0x</code>
283form remains as an alias.
Richard Smith855746b2011-11-28 20:02:05 +0000[diff] [blame]284
Chandler Carruthc00c0c32011-11-28 07:16:19 +0000[diff] [blame]285<!-- = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = -->
286<h3 id="objcchanges">Objective-C Language Changes in Clang</h3>
287<!-- = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = -->
Chandler Carruth4d582122011-11-29 00:15:23 +0000[diff] [blame]288Clang 3.0 introduces several new Objective-C language features and improvements.
289
290<h4 id="objc_arc">Objective-C Automatic Reference Counting</h4>
291<!-- This is really just a stub for John to flesh out regarding ARC. -->
292ARC provides automated memory management for Objective-C programs that is
293compatible with existing retain/release code. ARC is carefully built to
294be a reliable programming model that errs on the side of producing a
295compiler error instead of silently producing a runtime memory problem.
296ARC automates Objective-C objects, not malloc data, file descriptors,
297CoreFoundation datatypes or anything else. For more details, see the
298<a href="http://clang.llvm.org/docs/AutomaticReferenceCounting.html">full specification</a>.
299
300<h4 id="objc_instancetype">Objective-C Related Result Types / Instance
301Types</h4>
302Allows declaring new methods which follow the Cocoa conventions for methods
303such as <code>init</code> which always return objects that are an instance of
304the receiving class's type. For more details, see the
305<a href="http://clang.llvm.org/docs/LanguageExtensions.html#objc_instancetype">language extension documentation</a>.
Chandler Carruthc00c0c32011-11-28 07:16:19 +0000[diff] [blame]306
Chandler Carruth52e375e2011-11-29 00:15:25 +0000[diff] [blame]307<!--
308This is a stub for David Chisnall to fill out.
309
310<h4 id="objc_gnuruntime">Improved support for the GNU Runtime</h4>
311....
312-->
313
Chandler Carruthc00c0c32011-11-28 07:16:19 +0000[diff] [blame]314<!-- = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = -->
315<h3 id="apichanges">Internal API Changes</h3>
316<!-- = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = -->
317
Chandler Carruthc4dbffa2011-11-28 18:55:47 +0000[diff] [blame]318These are major API changes that have happened since the 2.9 release of Clang.
319If upgrading an external codebase that uses Clang as a library, this section
320should help get you past the largest hurdles of upgrading.
321
Chandler Carruth7d727b72011-11-28 19:06:34 +0000[diff] [blame]322<h4 id="macroexpansion">Switched terminology from "instantiation" to "expansion"
323 for macros</h4>
324A great deal of comments and code changes fell out of this, but also every API
325relating to macros with the word "instantiation" (or some variant thereof) was
326renamed. An incomplete list of the most note-worthy ones is here:
327<ul>
328 <li><code>MacroInstantiation</code> became <code>MacroExpansion</code></li>
329 <li><code>SourceManager::getInstantiationLoc</code> became
330 <code>SourceManager::getExpansionLoc</code></li>
331 <li><code>SourceManager::getInstantiationRange</code> became
332 <code>SourceManager::getExpansionRange</code></li>
333 <li><code>SourceManager::getImmediateInstantiationRange</code> became
334 <code>SourceManager::getImmediateExpansionRange</code></li>
335 <li><code>SourceManager::getDecomposedInstantiationLoc</code> became
336 <code>SourceManager::getDecomposedExpansionLoc</code></li>
337 <li><code>SourceManager::getInstantiationColumnNumber</code> became
338 <code>SourceManager::getExpansionColumnNumber</code></li>
339 <li><code>SourceManager::getInstantiationLineNumber</code> became
340 <code>SourceManager::getExpansionLineNumber</code></li>
341 <!-- TODO: Make this more complete! -->
342</ul>
343
Chandler Carruthc4dbffa2011-11-28 18:55:47 +0000[diff] [blame]344<h4 id="diagnosticrename">Diagnostic class names were shuffled</h4>
345<ul>
346 <li><code>Diagnostic</code> became <code>DiagnosticEngine</code></li>
347 <li><code>DiagnosticClient</code> became <code>DiagnosticConsumer</code></li>
348 <li><code>DiagnosticInfo</code> became <code>Diagnostic</code></li>
349</ul>
350Subclasses of <code>DiagnosticConsumer</code> were also then renamed to end with
351<code>Consumer</code>.
352
Chandler Carruthc00c0c32011-11-28 07:16:19 +0000[diff] [blame]353<!-- ======================================================================= -->
354<h2 id="knownproblems">Significant Known Problems</h2>
355<!-- ======================================================================= -->
356
357<!-- ======================================================================= -->
358<h2 id="additionalinfo">Additional Information</h2>
359<!-- ======================================================================= -->
360
361<p>A wide variety of additional information is available on the
362<a href="http://clang.llvm.org/">Clang web page</a>. The web page contains
363versions of the API documentation which are up-to-date with the Subversion
364version of the source code. You can access versions of these documents specific
365to this release by going into the "<tt>clang/doc/</tt>" directory in the Clang
366tree.</p>
367
368<p>If you have any questions or comments about Clang, please feel free to
369contact us via the <a href="http://lists.cs.uiuc.edu/mailman/listinfo/cfe-dev">
370mailing list</a>.</p>
371
Chandler Carruth59abf062011-11-28 22:12:44 +0000[diff] [blame]372
373<!-- ======================================================================= -->
374<!-- Likely 3.1 release notes -->
375<!-- ======================================================================= -->
376<!--
377This is just a section to hold things that have already gotten started and
378should likely pick up proper release notes in 3.1.
379
380- C1X and C++11 atomics infrastructure and support
381- CUDA support?
382
383-->
384
Chandler Carruthc00c0c32011-11-28 07:16:19 +0000[diff] [blame]385</body>
386</html>