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Diffstat (limited to 'docs/LanguageExtensions.html')
| -rw-r--r-- | docs/LanguageExtensions.html | 118 |
1 files changed, 104 insertions, 14 deletions
diff --git a/docs/LanguageExtensions.html b/docs/LanguageExtensions.html index b0de13a..f86835a 100644 --- a/docs/LanguageExtensions.html +++ b/docs/LanguageExtensions.html @@ -38,6 +38,8 @@ td { <li><a href="#cxx_deleted_functions">C++0x deleted functions</a></li> <li><a href="#cxx_lambdas">C++0x lambdas</a></li> <li><a href="#cxx_nullptr">C++0x nullptr</a></li> + <li><a href="#cxx_override_control">C++0x override control</a></li> + <li><a href="#cxx_range_for">C++0x range-based for loop</a></li> <li><a href="#cxx_rvalue_references">C++0x rvalue references</a></li> <li><a href="#cxx_reference_qualified_functions">C++0x reference-qualified functions</a></li> <li><a href="#cxx_static_assert">C++0x <tt>static_assert()</tt></a></li> @@ -46,14 +48,17 @@ td { <li><a href="#cxx_inline_namespaces">C++0x inline namespaces</a></li> <li><a href="#cxx_strong_enums">C++0x strongly-typed enumerations</a></li> <li><a href="#cxx_trailing_return">C++0x trailing return type</a></li> + <li><a href="#cxx_noexcept">C++0x noexcept specification</a></li> </ul> <li><a href="#checking_type_traits">Checks for Type Traits</a></li> <li><a href="#blocks">Blocks</a></li> <li><a href="#overloading-in-c">Function Overloading in C</a></li> +<li><a href="#generic-selections">Generic Selections</a></li> <li><a href="#builtins">Builtin Functions</a> <ul> <li><a href="#__builtin_shufflevector">__builtin_shufflevector</a></li> <li><a href="#__builtin_unreachable">__builtin_unreachable</a></li> + <li><a href="#__sync_swap">__sync_swap</a></li> </ul> </li> <li><a href="#targetspecific">Target-Specific Extensions</a> @@ -61,11 +66,7 @@ td { <li><a href="#x86-specific">X86/X86-64 Language Extensions</a></li> </ul> </li> -<li><a href="#analyzerspecific">Static Analysis-Specific Extensions</a> - <ul> - <li><a href="#analyzerattributes">Analyzer Attributes</a></li> - </ul> -</li> +<li><a href="#analyzerspecific">Static Analysis-Specific Extensions</a></li> </ul> <!-- ======================================================================= --> @@ -83,7 +84,7 @@ more information on these extensions.</p> <!-- ======================================================================= --> <p>Language extensions can be very useful, but only if you know you can depend -on them. In order to allow fine-grain features checks, we support two builtin +on them. In order to allow fine-grain features checks, we support three builtin function-like macros. This allows you to directly test for a feature in your code without having to resort to something like autoconf or fragile "compiler version checks".</p> @@ -402,9 +403,19 @@ lambdas is enabled. clang does not currently implement this feature.</p> <tt>nullptr</tt> is enabled. clang does not yet fully implement this feature.</p> +<h3 id="cxx_override_control">C++0x <tt>override control</tt></h3> + +<p>Use <tt>__has_feature(cxx_override_control)</tt> to determine if support for +the override control keywords is enabled.</p> + <h3 id="cxx_reference_qualified_functions">C++0x reference-qualified functions</h3> <p>Use <tt>__has_feature(cxx_reference_qualified_functions)</tt> to determine if support for reference-qualified functions (e.g., member functions with <code>&</code> or <code>&&</code> applied to <code>*this</code>) is enabled.</p> +<h3 id="cxx_range_for">C++0x range-based for loop</tt></h3> + +<p>Use <tt>__has_feature(cxx_range_for)</tt> to determine if support for +the range-based for loop is enabled. </p> + <h3 id="cxx_rvalue_references">C++0x rvalue references</tt></h3> <p>Use <tt>__has_feature(cxx_rvalue_references)</tt> to determine if support for @@ -436,6 +447,11 @@ inline namespaces is enabled.</p> <p>Use <tt>__has_feature(cxx_trailing_return)</tt> to determine if support for the alternate function declaration syntax with trailing return type is enabled.</p> +<h3 id="cxx_noexcept">C++0x noexcept</h3> + +<p>Use <tt>__has_feature(cxx_noexcept)</tt> to determine if support for +noexcept exception specifications is enabled.</p> + <h3 id="cxx_strong_enums">C++0x strongly typed enumerations</h3> <p>Use <tt>__has_feature(cxx_strong_enums)</tt> to determine if support for @@ -595,6 +611,20 @@ caveats to this use of name mangling:</p> <!-- ======================================================================= --> +<h2 id="generic-selections">Generic Selections</h2> +<!-- ======================================================================= --> + +<p>The C1X generic selection expression is available in all languages +supported by Clang. The syntax is the same as that given in the C1X draft +standard.</p> + +<p>In C, type compatibility is decided according to the rules given in the +appropriate standard, but in C++, which lacks the type compatibility rules +used in C, types are considered compatible only if they are equivalent.</p> + +<p>Query for this feature with __has_feature(generic_selections).</p> + +<!-- ======================================================================= --> <h2 id="builtins">Builtin Functions</h2> <!-- ======================================================================= --> @@ -703,6 +733,36 @@ no arguments and produces a void result. <p>Query for this feature with __has_builtin(__builtin_unreachable).</p> +<!-- ======================================================================= --> +<h3 id="__sync_swap">__sync_swap</h3> +<!-- ======================================================================= --> + +<p><tt>__sync_swap</tt> is used to atomically swap integers or pointers in +memory. +</p> + +<p><b>Syntax:</b></p> + +<pre> +<i>type</i> __sync_swap(<i>type</i> *ptr, <i>type</i> value, ...) +</pre> + +<p><b>Example of Use:</b></p> + +<pre> +int old_value = __sync_swap(&value, new_value); +</pre> + +<p><b>Description:</b></p> + +<p>The __sync_swap() builtin extends the existing __sync_*() family of atomic +intrinsics to allow code to atomically swap the current value with the new +value. More importantly, it helps developers write more efficient and correct +code by avoiding expensive loops around __sync_bool_compare_and_swap() or +relying on the platform specific implementation details of +__sync_lock_test_and_set(). The __sync_swap() builtin is a full barrier. +</p> + <!-- ======================================================================= --> <h2 id="targetspecific">Target-Specific Extensions</h2> @@ -754,11 +814,7 @@ are used by the <a href="http://clang.llvm.org/StaticAnalysis.html">path-sensitive static analyzer engine</a> that is part of Clang's Analysis library.</p> -<!-- ======================================================================= --> -<h3 id="analyzerattributes">Analyzer Attributes</h3> -<!-- ======================================================================= --> - -<h4 id="attr_analyzer_noreturn"><tt>analyzer_noreturn</tt></h4> +<h3 id="attr_analyzer_noreturn">The <tt>analyzer_noreturn</tt> attribute</h3> <p>Clang's static analysis engine understands the standard <tt>noreturn</tt> attribute. This attribute, which is typically affixed to a function prototype, @@ -786,16 +842,47 @@ placed at the end of function prototypes:</p> void foo() <b>__attribute__((analyzer_noreturn))</b>; </pre> -<p>Query for this feature with __has_feature(attribute_analyzer_noreturn).</p> +<p>Query for this feature with +<tt>__has_attribute(analyzer_noreturn)</tt>.</p> + +<h3 id="attr_method_family">The <tt>objc_method_family</tt> attribute</h3> -<h4 id="attr_retain_release">Objective-C retaining behavior attributes</h4> +<p>Many methods in Objective-C have conventional meanings determined +by their selectors. For the purposes of static analysis, it is +sometimes useful to be able to mark a method as having a particular +conventional meaning despite not having the right selector, or as not +having the conventional meaning that its selector would suggest. +For these use cases, we provide an attribute to specifically describe +the <q>method family</q> that a method belongs to.</p> + +<p><b>Usage</b>: <tt>__attribute__((objc_method_family(X)))</tt>, +where <tt>X</tt> is one of <tt>none</tt>, <tt>alloc</tt>, <tt>copy</tt>, +<tt>init</tt>, <tt>mutableCopy</tt>, or <tt>new</tt>. This attribute +can only be placed at the end of a method declaration:</p> + +<pre> + - (NSString*) initMyStringValue <b>__attribute__((objc_method_family(none)))</b>; +</pre> + +<p>Users who do not wish to change the conventional meaning of a +method, and who merely want to document its non-standard retain and +release semantics, should use the +<a href="#attr_retain_release">retaining behavior attributes</a> +described below.</p> + +<p>Query for this feature with +<tt>__has_attribute(objc_method_family)</tt>.</p> + +<h3 id="attr_retain_release">Objective-C retaining behavior attributes</h3> <p>In Objective-C, functions and methods are generally assumed to take and return objects with +0 retain counts, with some exceptions for special methods like <tt>+alloc</tt> and <tt>init</tt>. However, there are exceptions, and so Clang provides attributes to allow these exceptions to be documented, which helps the analyzer find leaks (and -ignore non-leaks).</p> +ignore non-leaks). Some exceptions may be better described using +the <a href="#attr_method_family"><tt>objc_method_family</tt></a> +attribute instead.</p> <p><b>Usage</b>: The <tt>ns_returns_retained</tt>, <tt>ns_returns_not_retained</tt>, <tt>ns_returns_autoreleased</tt>, <tt>cf_returns_retained</tt>, @@ -834,6 +921,9 @@ balance in some way.</p> - (void) baz: (id) <b>__attribute__((ns_consumed))</b> x; </pre> +<p>Query for these features with <tt>__has_attribute(ns_consumed)</tt>, +<tt>__has_attribute(ns_returns_retained)</tt>, etc.</p> + </div> </body> </html> |
