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 <a name="Objective_002dC-and-Objective_002dC_002b_002b-Dialect-Options"></a>
 <div class="header">
 <p>
 Next: <a href="Language-Independent-Options.html#Language-Independent-Options" accesskey="n" rel="next">Language Independent Options</a>, Previous: <a href="C_002b_002b-Dialect-Options.html#C_002b_002b-Dialect-Options" accesskey="p" rel="prev">C++ Dialect Options</a>, Up: <a href="Invoking-GCC.html#Invoking-GCC" accesskey="u" rel="up">Invoking GCC</a> &nbsp; [<a href="index.html#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="Option-Index.html#Option-Index" title="Index" rel="index">Index</a>]</p>
 </div>
 <hr>
 <a name="Options-Controlling-Objective_002dC-and-Objective_002dC_002b_002b-Dialects"></a>
 <h3 class="section">3.6 Options Controlling Objective-C and Objective-C++ Dialects</h3>

 <a name="index-compiler-options_002c-Objective_002dC-and-Objective_002dC_002b_002b"></a>
 <a name="index-Objective_002dC-and-Objective_002dC_002b_002b-options_002c-command_002dline"></a>
 <a name="index-options_002c-Objective_002dC-and-Objective_002dC_002b_002b"></a>
 <p>(NOTE: This manual does not describe the Objective-C and Objective-C++
 languages themselves.  See <a href="Standards.html#Standards">Language Standards
 Supported by GCC</a>, for references.)
 </p>
 <p>This section describes the command-line options that are only meaningful
 for Objective-C and Objective-C++ programs.  You can also use most of
 the language-independent GNU compiler options.
 For example, you might compile a file <code>some_class.m</code> like this:
 </p>
 <div class="smallexample">
 <pre class="smallexample">gcc -g -fgnu-runtime -O -c some_class.m
 </pre></div>

 <p>In this example, <samp>-fgnu-runtime</samp> is an option meant only for
 Objective-C and Objective-C++ programs; you can use the other options with
 any language supported by GCC.
 </p>
 <p>Note that since Objective-C is an extension of the C language, Objective-C
 compilations may also use options specific to the C front-end (e.g.,
 <samp>-Wtraditional</samp>).  Similarly, Objective-C++ compilations may use
 C++-specific options (e.g., <samp>-Wabi</samp>).
 </p>
 <p>Here is a list of options that are <em>only</em> for compiling Objective-C
 and Objective-C++ programs:
 </p>
 <dl compact="compact">
 <dt><code>-fconstant-string-class=<var>class-name</var></code></dt>
 <dd><a name="index-fconstant_002dstring_002dclass"></a>
 <p>Use <var>class-name</var> as the name of the class to instantiate for each
 literal string specified with the syntax <code>@&quot;&hellip;&quot;</code>.  The default
 class name is <code>NXConstantString</code> if the GNU runtime is being used, and
 <code>NSConstantString</code> if the NeXT runtime is being used (see below).  The
 <samp>-fconstant-cfstrings</samp> option, if also present, overrides the
 <samp>-fconstant-string-class</samp> setting and cause <code>@&quot;&hellip;&quot;</code> literals
 to be laid out as constant CoreFoundation strings.
 </p>
 </dd>
 <dt><code>-fgnu-runtime</code></dt>
 <dd><a name="index-fgnu_002druntime"></a>
 <p>Generate object code compatible with the standard GNU Objective-C
 runtime.  This is the default for most types of systems.
 </p>
 </dd>
 <dt><code>-fnext-runtime</code></dt>
 <dd><a name="index-fnext_002druntime"></a>
 <p>Generate output compatible with the NeXT runtime.  This is the default
 for NeXT-based systems, including Darwin and Mac OS X.  The macro
 <code>__NEXT_RUNTIME__</code> is predefined if (and only if) this option is
 used.
 </p>
 </dd>
 <dt><code>-fno-nil-receivers</code></dt>
 <dd><a name="index-fno_002dnil_002dreceivers"></a>
 <p>Assume that all Objective-C message dispatches (<code>[receiver
 message:arg]</code>) in this translation unit ensure that the receiver is
 not <code>nil</code>.  This allows for more efficient entry points in the
 runtime to be used.  This option is only available in conjunction with
 the NeXT runtime and ABI version 0 or 1.
 </p>
 </dd>
 <dt><code>-fobjc-abi-version=<var>n</var></code></dt>
 <dd><a name="index-fobjc_002dabi_002dversion"></a>
 <p>Use version <var>n</var> of the Objective-C ABI for the selected runtime.
 This option is currently supported only for the NeXT runtime.  In that
 case, Version 0 is the traditional (32-bit) ABI without support for
 properties and other Objective-C 2.0 additions.  Version 1 is the
 traditional (32-bit) ABI with support for properties and other
 Objective-C 2.0 additions.  Version 2 is the modern (64-bit) ABI.  If
 nothing is specified, the default is Version 0 on 32-bit target
 machines, and Version 2 on 64-bit target machines.
 </p>
 </dd>
 <dt><code>-fobjc-call-cxx-cdtors</code></dt>
 <dd><a name="index-fobjc_002dcall_002dcxx_002dcdtors"></a>
 <p>For each Objective-C class, check if any of its instance variables is a
 C++ object with a non-trivial default constructor.  If so, synthesize a
 special <code>- (id) .cxx_construct</code> instance method which runs
 non-trivial default constructors on any such instance variables, in order,
 and then return <code>self</code>.  Similarly, check if any instance variable
 is a C++ object with a non-trivial destructor, and if so, synthesize a
 special <code>- (void) .cxx_destruct</code> method which runs
 all such default destructors, in reverse order.
 </p>
 <p>The <code>- (id) .cxx_construct</code> and <code>- (void) .cxx_destruct</code>
 methods thusly generated only operate on instance variables
 declared in the current Objective-C class, and not those inherited
 from superclasses.  It is the responsibility of the Objective-C
 runtime to invoke all such methods in an object&rsquo;s inheritance
 hierarchy.  The <code>- (id) .cxx_construct</code> methods are invoked
 by the runtime immediately after a new object instance is allocated;
 the <code>- (void) .cxx_destruct</code> methods are invoked immediately
 before the runtime deallocates an object instance.
 </p>
 <p>As of this writing, only the NeXT runtime on Mac OS X 10.4 and later has
 support for invoking the <code>- (id) .cxx_construct</code> and
 <code>- (void) .cxx_destruct</code> methods.
 </p>
 </dd>
 <dt><code>-fobjc-direct-dispatch</code></dt>
 <dd><a name="index-fobjc_002ddirect_002ddispatch"></a>
 <p>Allow fast jumps to the message dispatcher.  On Darwin this is
 accomplished via the comm page.
 </p>
 </dd>
 <dt><code>-fobjc-exceptions</code></dt>
 <dd><a name="index-fobjc_002dexceptions"></a>
 <p>Enable syntactic support for structured exception handling in
 Objective-C, similar to what is offered by C++ and Java.  This option
 is required to use the Objective-C keywords <code>@try</code>,
 <code>@throw</code>, <code>@catch</code>, <code>@finally</code> and
 <code>@synchronized</code>.  This option is available with both the GNU
 runtime and the NeXT runtime (but not available in conjunction with
 the NeXT runtime on Mac OS X 10.2 and earlier).
 </p>
 </dd>
 <dt><code>-fobjc-gc</code></dt>
 <dd><a name="index-fobjc_002dgc"></a>
 <p>Enable garbage collection (GC) in Objective-C and Objective-C++
 programs.  This option is only available with the NeXT runtime; the
 GNU runtime has a different garbage collection implementation that
 does not require special compiler flags.
 </p>
 </dd>
 <dt><code>-fobjc-nilcheck</code></dt>
 <dd><a name="index-fobjc_002dnilcheck"></a>
 <p>For the NeXT runtime with version 2 of the ABI, check for a nil
 receiver in method invocations before doing the actual method call.
 This is the default and can be disabled using
 <samp>-fno-objc-nilcheck</samp>.  Class methods and super calls are never
 checked for nil in this way no matter what this flag is set to.
 Currently this flag does nothing when the GNU runtime, or an older
 version of the NeXT runtime ABI, is used.
 </p>
 </dd>
 <dt><code>-fobjc-std=objc1</code></dt>
 <dd><a name="index-fobjc_002dstd"></a>
 <p>Conform to the language syntax of Objective-C 1.0, the language
 recognized by GCC 4.0.  This only affects the Objective-C additions to
 the C/C++ language; it does not affect conformance to C/C++ standards,
 which is controlled by the separate C/C++ dialect option flags.  When
 this option is used with the Objective-C or Objective-C++ compiler,
 any Objective-C syntax that is not recognized by GCC 4.0 is rejected.
 This is useful if you need to make sure that your Objective-C code can
 be compiled with older versions of GCC.
 </p>
 </dd>
 <dt><code>-freplace-objc-classes</code></dt>
 <dd><a name="index-freplace_002dobjc_002dclasses"></a>
 <p>Emit a special marker instructing <code>ld(1)</code> not to statically link in
 the resulting object file, and allow <code>dyld(1)</code> to load it in at
 run time instead.  This is used in conjunction with the Fix-and-Continue
 debugging mode, where the object file in question may be recompiled and
 dynamically reloaded in the course of program execution, without the need
 to restart the program itself.  Currently, Fix-and-Continue functionality
 is only available in conjunction with the NeXT runtime on Mac OS X 10.3
 and later.
 </p>
 </dd>
 <dt><code>-fzero-link</code></dt>
 <dd><a name="index-fzero_002dlink"></a>
 <p>When compiling for the NeXT runtime, the compiler ordinarily replaces calls
 to <code>objc_getClass(&quot;&hellip;&quot;)</code> (when the name of the class is known at
 compile time) with static class references that get initialized at load time,
 which improves run-time performance.  Specifying the <samp>-fzero-link</samp> flag
 suppresses this behavior and causes calls to <code>objc_getClass(&quot;&hellip;&quot;)</code>
 to be retained.  This is useful in Zero-Link debugging mode, since it allows
 for individual class implementations to be modified during program execution.
 The GNU runtime currently always retains calls to <code>objc_get_class(&quot;&hellip;&quot;)</code>
 regardless of command-line options.
 </p>
 </dd>
 <dt><code>-gen-decls</code></dt>
 <dd><a name="index-gen_002ddecls"></a>
 <p>Dump interface declarations for all classes seen in the source file to a
 file named <samp><var>sourcename</var>.decl</samp>.
 </p>
 </dd>
 <dt><code>-Wassign-intercept <span class="roman">(Objective-C and Objective-C++ only)</span></code></dt>
 <dd><a name="index-Wassign_002dintercept"></a>
 <a name="index-Wno_002dassign_002dintercept"></a>
 <p>Warn whenever an Objective-C assignment is being intercepted by the
 garbage collector.
 </p>
 </dd>
 <dt><code>-Wno-protocol <span class="roman">(Objective-C and Objective-C++ only)</span></code></dt>
 <dd><a name="index-Wno_002dprotocol"></a>
 <a name="index-Wprotocol"></a>
 <p>If a class is declared to implement a protocol, a warning is issued for
 every method in the protocol that is not implemented by the class.  The
 default behavior is to issue a warning for every method not explicitly
 implemented in the class, even if a method implementation is inherited
 from the superclass.  If you use the <samp>-Wno-protocol</samp> option, then
 methods inherited from the superclass are considered to be implemented,
 and no warning is issued for them.
 </p>
 </dd>
 <dt><code>-Wselector <span class="roman">(Objective-C and Objective-C++ only)</span></code></dt>
 <dd><a name="index-Wselector"></a>
 <a name="index-Wno_002dselector"></a>
 <p>Warn if multiple methods of different types for the same selector are
 found during compilation.  The check is performed on the list of methods
 in the final stage of compilation.  Additionally, a check is performed
 for each selector appearing in a <code>@selector(&hellip;)</code>
 expression, and a corresponding method for that selector has been found
 during compilation.  Because these checks scan the method table only at
 the end of compilation, these warnings are not produced if the final
 stage of compilation is not reached, for example because an error is
 found during compilation, or because the <samp>-fsyntax-only</samp> option is
 being used.
 </p>
 </dd>
 <dt><code>-Wstrict-selector-match <span class="roman">(Objective-C and Objective-C++ only)</span></code></dt>
 <dd><a name="index-Wstrict_002dselector_002dmatch"></a>
 <a name="index-Wno_002dstrict_002dselector_002dmatch"></a>
 <p>Warn if multiple methods with differing argument and/or return types are
 found for a given selector when attempting to send a message using this
 selector to a receiver of type <code>id</code> or <code>Class</code>.  When this flag
 is off (which is the default behavior), the compiler omits such warnings
 if any differences found are confined to types that share the same size
 and alignment.
 </p>
 </dd>
 <dt><code>-Wundeclared-selector <span class="roman">(Objective-C and Objective-C++ only)</span></code></dt>
 <dd><a name="index-Wundeclared_002dselector"></a>
 <a name="index-Wno_002dundeclared_002dselector"></a>
 <p>Warn if a <code>@selector(&hellip;)</code> expression referring to an
 undeclared selector is found.  A selector is considered undeclared if no
 method with that name has been declared before the
 <code>@selector(&hellip;)</code> expression, either explicitly in an
 <code>@interface</code> or <code>@protocol</code> declaration, or implicitly in
 an <code>@implementation</code> section.  This option always performs its
 checks as soon as a <code>@selector(&hellip;)</code> expression is found,
 while <samp>-Wselector</samp> only performs its checks in the final stage of
 compilation.  This also enforces the coding style convention
 that methods and selectors must be declared before being used.
 </p>
 </dd>
 <dt><code>-print-objc-runtime-info</code></dt>
 <dd><a name="index-print_002dobjc_002druntime_002dinfo"></a>
 <p>Generate C header describing the largest structure that is passed by
 value, if any.
 </p>
 </dd>
 </dl>

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	<div class="header">
	<p>
	Next: <a href="Language-Independent-Options.html#Language-Independent-Options" accesskey="n" rel="next">Language Independent Options</a>, Previous: <a href="C_002b_002b-Dialect-Options.html#C_002b_002b-Dialect-Options" accesskey="p" rel="prev">C++ Dialect Options</a>, Up: <a href="Invoking-GCC.html#Invoking-GCC" accesskey="u" rel="up">Invoking GCC</a>   [<a href="index.html#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="Option-Index.html#Option-Index" title="Index" rel="index">Index</a>]</p>
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	<a name="Options-Controlling-Objective_002dC-and-Objective_002dC_002b_002b-Dialects"></a>
	<h3 class="section">3.6 Options Controlling Objective-C and Objective-C++ Dialects</h3>

	<a name="index-compiler-options_002c-Objective_002dC-and-Objective_002dC_002b_002b"></a>
	<a name="index-Objective_002dC-and-Objective_002dC_002b_002b-options_002c-command_002dline"></a>
	<a name="index-options_002c-Objective_002dC-and-Objective_002dC_002b_002b"></a>
	<p>(NOTE: This manual does not describe the Objective-C and Objective-C++
	languages themselves. See <a href="Standards.html#Standards">Language Standards
	Supported by GCC</a>, for references.)
	</p>
	<p>This section describes the command-line options that are only meaningful
	for Objective-C and Objective-C++ programs. You can also use most of
	the language-independent GNU compiler options.
	For example, you might compile a file <code>some_class.m</code> like this:
	</p>
	<div class="smallexample">
	<pre class="smallexample">gcc -g -fgnu-runtime -O -c some_class.m
	</pre></div>

	<p>In this example, <samp>-fgnu-runtime</samp> is an option meant only for
	Objective-C and Objective-C++ programs; you can use the other options with
	any language supported by GCC.
	</p>
	<p>Note that since Objective-C is an extension of the C language, Objective-C
	compilations may also use options specific to the C front-end (e.g.,
	<samp>-Wtraditional</samp>). Similarly, Objective-C++ compilations may use
	C++-specific options (e.g., <samp>-Wabi</samp>).
	</p>
	<p>Here is a list of options that are <em>only</em> for compiling Objective-C
	and Objective-C++ programs:
	</p>
	<dl compact="compact">
	<dt><code>-fconstant-string-class=<var>class-name</var></code></dt>
	<dd><a name="index-fconstant_002dstring_002dclass"></a>
	<p>Use <var>class-name</var> as the name of the class to instantiate for each
	literal string specified with the syntax <code>@"…"</code>. The default
	class name is <code>NXConstantString</code> if the GNU runtime is being used, and
	<code>NSConstantString</code> if the NeXT runtime is being used (see below). The
	<samp>-fconstant-cfstrings</samp> option, if also present, overrides the
	<samp>-fconstant-string-class</samp> setting and cause <code>@"…"</code> literals
	to be laid out as constant CoreFoundation strings.
	</p>
	</dd>
	<dt><code>-fgnu-runtime</code></dt>
	<dd><a name="index-fgnu_002druntime"></a>
	<p>Generate object code compatible with the standard GNU Objective-C
	runtime. This is the default for most types of systems.
	</p>
	</dd>
	<dt><code>-fnext-runtime</code></dt>
	<dd><a name="index-fnext_002druntime"></a>
	<p>Generate output compatible with the NeXT runtime. This is the default
	for NeXT-based systems, including Darwin and Mac OS X. The macro
	<code>__NEXT_RUNTIME__</code> is predefined if (and only if) this option is
	used.
	</p>
	</dd>
	<dt><code>-fno-nil-receivers</code></dt>
	<dd><a name="index-fno_002dnil_002dreceivers"></a>
	<p>Assume that all Objective-C message dispatches (<code>[receiver
	message:arg]</code>) in this translation unit ensure that the receiver is
	not <code>nil</code>. This allows for more efficient entry points in the
	runtime to be used. This option is only available in conjunction with
	the NeXT runtime and ABI version 0 or 1.
	</p>
	</dd>
	<dt><code>-fobjc-abi-version=<var>n</var></code></dt>
	<dd><a name="index-fobjc_002dabi_002dversion"></a>
	<p>Use version <var>n</var> of the Objective-C ABI for the selected runtime.
	This option is currently supported only for the NeXT runtime. In that
	case, Version 0 is the traditional (32-bit) ABI without support for
	properties and other Objective-C 2.0 additions. Version 1 is the
	traditional (32-bit) ABI with support for properties and other
	Objective-C 2.0 additions. Version 2 is the modern (64-bit) ABI. If
	nothing is specified, the default is Version 0 on 32-bit target
	machines, and Version 2 on 64-bit target machines.
	</p>
	</dd>
	<dt><code>-fobjc-call-cxx-cdtors</code></dt>
	<dd><a name="index-fobjc_002dcall_002dcxx_002dcdtors"></a>
	<p>For each Objective-C class, check if any of its instance variables is a
	C++ object with a non-trivial default constructor. If so, synthesize a
	special <code>- (id) .cxx_construct</code> instance method which runs
	non-trivial default constructors on any such instance variables, in order,
	and then return <code>self</code>. Similarly, check if any instance variable
	is a C++ object with a non-trivial destructor, and if so, synthesize a
	special <code>- (void) .cxx_destruct</code> method which runs
	all such default destructors, in reverse order.
	</p>
	<p>The <code>- (id) .cxx_construct</code> and <code>- (void) .cxx_destruct</code>
	methods thusly generated only operate on instance variables
	declared in the current Objective-C class, and not those inherited
	from superclasses. It is the responsibility of the Objective-C
	runtime to invoke all such methods in an object’s inheritance
	hierarchy. The <code>- (id) .cxx_construct</code> methods are invoked
	by the runtime immediately after a new object instance is allocated;
	the <code>- (void) .cxx_destruct</code> methods are invoked immediately
	before the runtime deallocates an object instance.
	</p>
	<p>As of this writing, only the NeXT runtime on Mac OS X 10.4 and later has
	support for invoking the <code>- (id) .cxx_construct</code> and
	<code>- (void) .cxx_destruct</code> methods.
	</p>
	</dd>
	<dt><code>-fobjc-direct-dispatch</code></dt>
	<dd><a name="index-fobjc_002ddirect_002ddispatch"></a>
	<p>Allow fast jumps to the message dispatcher. On Darwin this is
	accomplished via the comm page.
	</p>
	</dd>
	<dt><code>-fobjc-exceptions</code></dt>
	<dd><a name="index-fobjc_002dexceptions"></a>
	<p>Enable syntactic support for structured exception handling in
	Objective-C, similar to what is offered by C++ and Java. This option
	is required to use the Objective-C keywords <code>@try</code>,
	<code>@throw</code>, <code>@catch</code>, <code>@finally</code> and
	<code>@synchronized</code>. This option is available with both the GNU
	runtime and the NeXT runtime (but not available in conjunction with
	the NeXT runtime on Mac OS X 10.2 and earlier).
	</p>
	</dd>
	<dt><code>-fobjc-gc</code></dt>
	<dd><a name="index-fobjc_002dgc"></a>
	<p>Enable garbage collection (GC) in Objective-C and Objective-C++
	programs. This option is only available with the NeXT runtime; the
	GNU runtime has a different garbage collection implementation that
	does not require special compiler flags.
	</p>
	</dd>
	<dt><code>-fobjc-nilcheck</code></dt>
	<dd><a name="index-fobjc_002dnilcheck"></a>
	<p>For the NeXT runtime with version 2 of the ABI, check for a nil
	receiver in method invocations before doing the actual method call.
	This is the default and can be disabled using
	<samp>-fno-objc-nilcheck</samp>. Class methods and super calls are never
	checked for nil in this way no matter what this flag is set to.
	Currently this flag does nothing when the GNU runtime, or an older
	version of the NeXT runtime ABI, is used.
	</p>
	</dd>
	<dt><code>-fobjc-std=objc1</code></dt>
	<dd><a name="index-fobjc_002dstd"></a>
	<p>Conform to the language syntax of Objective-C 1.0, the language
	recognized by GCC 4.0. This only affects the Objective-C additions to
	the C/C++ language; it does not affect conformance to C/C++ standards,
	which is controlled by the separate C/C++ dialect option flags. When
	this option is used with the Objective-C or Objective-C++ compiler,
	any Objective-C syntax that is not recognized by GCC 4.0 is rejected.
	This is useful if you need to make sure that your Objective-C code can
	be compiled with older versions of GCC.
	</p>
	</dd>
	<dt><code>-freplace-objc-classes</code></dt>
	<dd><a name="index-freplace_002dobjc_002dclasses"></a>
	<p>Emit a special marker instructing <code>ld(1)</code> not to statically link in
	the resulting object file, and allow <code>dyld(1)</code> to load it in at
	run time instead. This is used in conjunction with the Fix-and-Continue
	debugging mode, where the object file in question may be recompiled and
	dynamically reloaded in the course of program execution, without the need
	to restart the program itself. Currently, Fix-and-Continue functionality
	is only available in conjunction with the NeXT runtime on Mac OS X 10.3
	and later.
	</p>
	</dd>
	<dt><code>-fzero-link</code></dt>
	<dd><a name="index-fzero_002dlink"></a>
	<p>When compiling for the NeXT runtime, the compiler ordinarily replaces calls
	to <code>objc_getClass("…")</code> (when the name of the class is known at
	compile time) with static class references that get initialized at load time,
	which improves run-time performance. Specifying the <samp>-fzero-link</samp> flag
	suppresses this behavior and causes calls to <code>objc_getClass("…")</code>
	to be retained. This is useful in Zero-Link debugging mode, since it allows
	for individual class implementations to be modified during program execution.
	The GNU runtime currently always retains calls to <code>objc_get_class("…")</code>
	regardless of command-line options.
	</p>
	</dd>
	<dt><code>-gen-decls</code></dt>
	<dd><a name="index-gen_002ddecls"></a>
	<p>Dump interface declarations for all classes seen in the source file to a
	file named <samp><var>sourcename</var>.decl</samp>.
	</p>
	</dd>
	<dt><code>-Wassign-intercept <span class="roman">(Objective-C and Objective-C++ only)</span></code></dt>
	<dd><a name="index-Wassign_002dintercept"></a>
	<a name="index-Wno_002dassign_002dintercept"></a>
	<p>Warn whenever an Objective-C assignment is being intercepted by the
	garbage collector.
	</p>
	</dd>
	<dt><code>-Wno-protocol <span class="roman">(Objective-C and Objective-C++ only)</span></code></dt>
	<dd><a name="index-Wno_002dprotocol"></a>
	<a name="index-Wprotocol"></a>
	<p>If a class is declared to implement a protocol, a warning is issued for
	every method in the protocol that is not implemented by the class. The
	default behavior is to issue a warning for every method not explicitly
	implemented in the class, even if a method implementation is inherited
	from the superclass. If you use the <samp>-Wno-protocol</samp> option, then
	methods inherited from the superclass are considered to be implemented,
	and no warning is issued for them.
	</p>
	</dd>
	<dt><code>-Wselector <span class="roman">(Objective-C and Objective-C++ only)</span></code></dt>
	<dd><a name="index-Wselector"></a>
	<a name="index-Wno_002dselector"></a>
	<p>Warn if multiple methods of different types for the same selector are
	found during compilation. The check is performed on the list of methods
	in the final stage of compilation. Additionally, a check is performed
	for each selector appearing in a <code>@selector(…)</code>
	expression, and a corresponding method for that selector has been found
	during compilation. Because these checks scan the method table only at
	the end of compilation, these warnings are not produced if the final
	stage of compilation is not reached, for example because an error is
	found during compilation, or because the <samp>-fsyntax-only</samp> option is
	being used.
	</p>
	</dd>
	<dt><code>-Wstrict-selector-match <span class="roman">(Objective-C and Objective-C++ only)</span></code></dt>
	<dd><a name="index-Wstrict_002dselector_002dmatch"></a>
	<a name="index-Wno_002dstrict_002dselector_002dmatch"></a>
	<p>Warn if multiple methods with differing argument and/or return types are
	found for a given selector when attempting to send a message using this
	selector to a receiver of type <code>id</code> or <code>Class</code>. When this flag
	is off (which is the default behavior), the compiler omits such warnings
	if any differences found are confined to types that share the same size
	and alignment.
	</p>
	</dd>
	<dt><code>-Wundeclared-selector <span class="roman">(Objective-C and Objective-C++ only)</span></code></dt>
	<dd><a name="index-Wundeclared_002dselector"></a>
	<a name="index-Wno_002dundeclared_002dselector"></a>
	<p>Warn if a <code>@selector(…)</code> expression referring to an
	undeclared selector is found. A selector is considered undeclared if no
	method with that name has been declared before the
	<code>@selector(…)</code> expression, either explicitly in an
	<code>@interface</code> or <code>@protocol</code> declaration, or implicitly in
	an <code>@implementation</code> section. This option always performs its
	checks as soon as a <code>@selector(…)</code> expression is found,
	while <samp>-Wselector</samp> only performs its checks in the final stage of
	compilation. This also enforces the coding style convention
	that methods and selectors must be declared before being used.
	</p>
	</dd>
	<dt><code>-print-objc-runtime-info</code></dt>
	<dd><a name="index-print_002dobjc_002druntime_002dinfo"></a>
	<p>Generate C header describing the largest structure that is passed by
	value, if any.
	</p>
	</dd>
	</dl>

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