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| <h1>Clang 3.2 Release Notes</h1> |
| |
| <img style="float:right" src="http://llvm.org/img/DragonSmall.png" |
| width="136" height="136" alt="LLVM Dragon Logo"> |
| |
| <ul> |
| <li><a href="#intro">Introduction</a></li> |
| <li><a href="#whatsnew">What's New in Clang 3.2?</a> |
| <ul> |
| <li><a href="#majorfeatures">Major New Features</a></li> |
| <li><a href="#newflags">New Compiler Flags</a></li> |
| <li><a href="#cchanges">C Language Changes</a></li> |
| <li><a href="#cxxchanges">C++ Language Changes</a></li> |
| <li><a href="#objcchanges">Objective-C Language Changes</a></li> |
| <li><a href="#apichanges">Internal API Changes</a></li> |
| <li><a href="#pythonchanges">Python Binding Changes</a></li> |
| </ul> |
| </li> |
| <li><a href="#knownproblems">Known Problems</a></li> |
| <li><a href="#additionalinfo">Additional Information</a></li> |
| </ul> |
| |
| <div class="doc_author"> |
| <p>Written by the <a href="http://llvm.org/">LLVM Team</a></p> |
| </div> |
| |
| <h1 style="color:red">These are in-progress notes for the upcoming Clang 3.2 |
| release.<br> |
| You may prefer the |
| <a href="http://llvm.org/releases/3.1/docs/ClangReleaseNotes.html">Clang 3.1 |
| Release Notes</a>.</h1> |
| |
| <!-- ======================================================================= --> |
| <h2 id="intro">Introduction</h2> |
| <!-- ======================================================================= --> |
| |
| <p>This document contains the release notes for the Clang C/C++/Objective-C |
| frontend, part of the LLVM Compiler Infrastructure, release 3.2. Here we |
| describe the status of Clang in some detail, including major improvements |
| from the previous release and new feature work. For the general LLVM release |
| notes, see <a href="http://llvm.org/docs/ReleaseNotes.html">the LLVM |
| documentation</a>. All LLVM releases may be downloaded from the |
| <a href="http://llvm.org/releases/">LLVM releases web site</a>.</p> |
| |
| <p>For more information about Clang or LLVM, including information about the |
| latest release, please check out the main please see the |
| <a href="http://clang.llvm.org">Clang Web Site</a> or the |
| <a href="http://llvm.org">LLVM Web Site</a>. |
| |
| <p>Note that if you are reading this file from a Subversion checkout or the main |
| Clang web page, this document applies to the <i>next</i> release, not the |
| current one. To see the release notes for a specific release, please see the |
| <a href="http://llvm.org/releases/">releases page</a>.</p> |
| |
| <!-- ======================================================================= --> |
| <h2 id="whatsnew">What's New in Clang 3.2?</h2> |
| <!-- ======================================================================= --> |
| |
| <p>Some of the major new features and improvements to Clang are listed here. |
| Generic improvements to Clang as a whole or to its underlying infrastructure |
| are described first, followed by language-specific sections with improvements |
| to Clang's support for those languages.</p> |
| |
| <!-- = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = --> |
| <h3 id="majorfeatures">Major New Features</h3> |
| <!-- = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = --> |
| |
| <h4 id="diagnostics">Improvements to Clang's diagnostics</h4> |
| |
| <p>Clang's diagnostics are constantly being improved to catch more issues, |
| explain them more clearly, and provide more accurate source information about |
| them. The improvements since the 3.1 release include:</p> |
| |
| <ul> |
| <li><tt>-Wuninitialized</tt> has been taught to recognise uninitialized uses |
| which always occur when an explicitly-written non-constant condition is either |
| <tt>true</tt> or <tt>false</tt>. For example: |
| |
| <pre> |
| int f(bool b) { |
| int n; |
| if (b) |
| n = 1; |
| return n; |
| } |
| |
| <b>sometimes-uninit.cpp:3:7: <span class="warning">warning:</span> variable 'n' is used uninitialized whenever 'if' condition is false [-Wsometimes-uninitialized]</b> |
| if (b) |
| <span class="caret">^</span> |
| <b>sometimes-uninit.cpp:5:10: <span class="note">note:</span></b> uninitialized use occurs here |
| return n; |
| <span class="caret">^</span> |
| <b>sometimes-uninit.cpp:3:3: <span class="note">note:</span></b> remove the 'if' if its condition is always true |
| if (b) |
| <span class="caret">^~~~~~</span> |
| <b>sometimes-uninit.cpp:2:8: <span class="note">note:</span></b> initialize the variable 'n' to silence this warning |
| int n; |
| <span class="caret">^</span> |
| <span class="caret"> = 0</span> |
| </pre> |
| |
| This functionality can be enabled or disabled separately from |
| <tt>-Wuninitialized</tt> with the <tt>-Wsometimes-uninitialized</tt> warning |
| flag.</li> |
| |
| <li>Template type diffing improves the display of diagnostics with templated |
| types in them. |
| |
| <pre> |
| int f(vector<map<int, double>>); |
| int x = f(vector<map<int, float>>()); |
| </pre> |
| The error message is the same, but the note is different based on the options selected. |
| <pre> |
| <b>template-diff.cpp:5:9: <span class="error">error:</span> no matching function for call to 'f'</b> |
| int x = f(vector<map<int, float>>()); |
| <span class="caret">^</span> |
| </pre> |
| Templated type diffing with type elision (default): |
| <pre> |
| <b>template-diff.cpp:4:5: <span class="note">note:</span></b> candidate function not viable: no known conversion from 'vector<map<[...], <span class="template-highlight">float</span>>>' to 'vector<map<[...], <span class="template-highlight">double</span>>>' for 1st argument; |
| int f(vector<map<int, double>>); |
| <span class="caret">^</span> |
| </pre> |
| Templated type diffing without type elision (-fno-elide-type): |
| <pre> |
| <b>template-diff.cpp:4:5: <span class="note">note:</span></b> candidate function not viable: no known conversion from 'vector<map<int, <span class="template-highlight">float</span>>>' to 'vector<map<int, <span class="template-highlight">double</span>>>' for 1st argument; |
| int f(vector<map<int, double>>); |
| <span class="caret">^</span> |
| </pre> |
| Templated tree printing with type elision (-fdiagnostics-show-template-tree): |
| <pre> |
| <b>template-diff.cpp:4:5: <span class="note">note:</span></b> candidate function not viable: no known conversion for 1st argument; |
| vector< |
| map< |
| [...], |
| [<span class="template-highlight">float</span> != <span class="template-highlight">double</span>]>> |
| int f(vector<map<int, double>>); |
| <span class="caret">^</span> |
| </pre> |
| Templated tree printing without type elision (-fdiagnostics-show-template-tree -fno-elide-type): |
| <pre> |
| <b>template-diff.cpp:4:5: <span class="note">note:</span></b> candidate function not viable: no known conversion for 1st argument; |
| vector< |
| map< |
| int, |
| [<span class="template-highlight">float</span> != <span class="template-highlight">double</span>]>> |
| int f(vector<map<int, double>>); |
| <span class="caret">^</span> |
| </pre> |
| |
| </li> |
| |
| <li>Clang's <tt>-fcatch-undefined-behavior</tt> option has grown the ability |
| to check for several new types of undefined behavior. |
| |
| <!-- Flesh this out prior to release. --> |
| |
| </li> |
| |
| </ul> |
| |
| <h4 id="tlsmodel">Support for <code>tls_model</code> attribute</h4> |
| |
| <p>Clang now supports the <code>tls_model</code> attribute, allowing code that |
| uses thread-local storage to explicitly select which model to use. The available |
| models are <code>"global-dynamic"</code>, <code>"local-dynamic"</code>, |
| <code>"initial-exec"</code> and <code>"local-exec"</code>. See |
| <a href="http://www.akkadia.org/drepper/tls.pdf">ELF Handling For Thread-Local |
| Storage</a> for more information.</p> |
| |
| <p>The compiler is free to choose a different model if the specified model is not |
| supported by the target, or if the compiler determines that a more specific |
| model can be used. |
| </p> |
| |
| <h4>Type safety attributes</h4> |
| <p>Clang now supports type safety attributes that allow checking during compile |
| time that 'void *' function arguments and arguments for variadic functions are |
| of a particular type which is determined by some other argument to the same |
| function call.</p> |
| |
| <p>Usecases include:</p> |
| <ul> |
| <li>MPI library implementations, where these attributes enable checking that |
| buffer type matches the passed <code>MPI_Datatype</code>;</li> |
| <li> HDF5 library -- similar usecase as for MPI;</li> |
| <li> checking types of variadic functions' arguments for functions like |
| <code>fcntl()</code> and <code>ioctl()</code>.</li> |
| </ul> |
| |
| <p>See entries for <code>argument_with_type_tag</code>, |
| <code>pointer_with_type_tag</code> and <code>type_tag_for_datatype</code> |
| attributes in Clang language extensions documentation.</p> |
| |
| <!-- = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = --> |
| <h3 id="newflags">New Compiler Flags</h3> |
| <!-- = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = --> |
| <ul> |
| <li><tt>-gline-tables-only</tt> controls the |
| <a href="http://clang.llvm.org/docs/UsersManual.html#debuginfosize">size of debug information</a>. |
| This flag tells Clang to emit debug info which is just enough to obtain stack traces with |
| function names, file names and line numbers (by such tools as gdb or addr2line). |
| Debug info for variables or function parameters is not produced, which reduces |
| the size of the resulting binary. |
| |
| <li><tt>-ftls-model</tt> controls which TLS model to use for thread-local |
| variables. This can be overridden per variable using the |
| <a href="#tlsmodel"><tt>tls_model</tt> attribute</a> mentioned above. |
| For more details, see the <a href="UsersManual.html#opt_ftls-model">User's |
| Manual</a>.</li> |
| </ul> |
| |
| <!-- = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = --> |
| <h3 id="cchanges">C Language Changes in Clang</h3> |
| <!-- = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = --> |
| |
| <h4 id="c11changes">C11 Feature Support</h4> |
| |
| <p>...</p> |
| |
| <!-- = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = --> |
| <h3 id="cxxchanges">C++ Language Changes in Clang</h3> |
| <!-- = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = --> |
| |
| <h4 id="cxx11changes">C++11 Feature Support</h4> |
| |
| <p>...</p> |
| |
| <!-- = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = --> |
| <h3 id="objcchanges">Objective-C Language Changes in Clang</h3> |
| <!-- = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = --> |
| |
| <p>...</p> |
| |
| <!-- = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = --> |
| <h3 id="apichanges">Internal API Changes</h3> |
| <!-- = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = --> |
| |
| <p>These are major API changes that have happened since the 3.1 release of |
| Clang. If upgrading an external codebase that uses Clang as a library, this |
| section should help get you past the largest hurdles of upgrading.</p> |
| |
| <h4 id="api1">API change 1</h4> |
| |
| <p>...</p> |
| |
| <!-- = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = --> |
| <h3 id="pythonchanges">Python Binding Changes</h3> |
| <!-- = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = --> |
| |
| The following methods have been added: |
| <ul> |
| <li>...</li> |
| </ul> |
| |
| <!-- ======================================================================= --> |
| <h2 id="knownproblems">Significant Known Problems</h2> |
| <!-- ======================================================================= --> |
| |
| <!-- ======================================================================= --> |
| <h2 id="additionalinfo">Additional Information</h2> |
| <!-- ======================================================================= --> |
| |
| <p>A wide variety of additional information is available on the |
| <a href="http://clang.llvm.org/">Clang web page</a>. The web page contains |
| versions of the API documentation which are up-to-date with the Subversion |
| version of the source code. You can access versions of these documents |
| specific to this release by going into the "<tt>clang/doc/</tt>" directory in |
| the Clang tree.</p> |
| |
| <p>If you have any questions or comments about Clang, please feel free to |
| contact us via |
| the <a href="http://lists.cs.uiuc.edu/mailman/listinfo/cfe-dev"> mailing |
| list</a>.</p> |
| |
| <!-- ======================================================================= --> |
| <!-- Likely 3.1 release notes --> |
| <!-- ======================================================================= --> |
| <!-- |
| This is just a section to hold things that have already gotten started and |
| should likely pick up proper release notes in 3.1. |
| |
| - C1X and C++11 atomics infrastructure and support |
| - CUDA support? |
| |
| --> |
| |
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