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238 lines
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HTML
238 lines
6.2 KiB
HTML
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN"
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"http://www.w3.org/TR/html4/strict.dtd">
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<html>
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<head>
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<meta http-equiv="Content-Type" content="text/html; charset=utf-8">
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<title>Debugging Information Extension for Objective C Properties</title>
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<link rel="stylesheet" href="llvm.css" type="text/css">
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</head>
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<body>
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<h1>
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Debugging Information Extension for Objective C Properties
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</h1>
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<ol>
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<li><a href="#introduction">Introduction</a></li>
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<li><a href="#proposal">Proposal</a></li>
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<li><a href="#newattributes">New DWARF Attributes</a></li>
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<li><a href="#newconstants">New DWARF Constants</a></li>
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</ol>
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<div class="doc_author">
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<p>Written by Jim Ingham and Devang Patel </p>
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</div>
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<!-- *********************************************************************** -->
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<h2>
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<a name="introduction">Introduction</a>
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</h2>
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<!-- *********************************************************************** -->
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<div>
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<p>Objective C provides a simpler way to declare and define accessor methods
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using declared properties. The language provides features to declare a
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property and to let compiler synthesize accessor methods.
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</p>
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<p>The debugger lets developer inspect Objective C interfaces and their
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instance variables and class variables. However, the debugger does not know
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anything about the properties defined in Objective C interfaces. The debugger
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consumes information generated by compiler in DWARF format. The format does
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not support encoding of Objective C properties. This proposal describes DWARF
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extensions to encode Objective C properties, which the debugger can use to let
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developers inspect Objective C properties.
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</p>
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</div>
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<!-- *********************************************************************** -->
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<h2>
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<a name="proposal">Proposal</a>
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</h2>
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<!-- *********************************************************************** -->
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<div>
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<p>Objective C properties are always backed by an instance variable. The
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instance variables backing properties are identified using
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DW_AT_APPLE_property_name attribute. The instance variables with this
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attribute may not have data location attributes. The location of instance
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variables is determined by debugger only after consulting Objective C runtime.
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</p>
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<div class="doc_code">
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<pre>
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@interface I1 {
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int n2;
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}
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@property p1;
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@property p2;
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@end
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@implementation I1
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@synthesize p1;
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@synthesize p2 = n2;
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@end
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TAG_structure_type [7] *
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AT_APPLE_runtime_class( 0x10 )
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AT_name( "I1" )
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AT_decl_file( "Objc_Property.m" )
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AT_decl_line( 3 )
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TAG_member [8]
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AT_name( "p1" )
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AT_APPLE_property_name(“p1”)
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AT_type( {0x00000147} ( int ) )
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TAG_member [8]
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AT_name( "n2" )
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AT_APPLE_property_name(“p2”)
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AT_type( {0x00000147} ( int ) )
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</pre>
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</div>
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<p> Developers can decorate a property with attributes which are encoded using
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DW_AT_APPLE_property_attribute.
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</p>
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<div class="doc_code">
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<pre>
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@property (readonly, nonatomic) int pr;
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TAG_member [8]
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AT_name(“pr”)
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AT_APPLE_property_name(“pr”)
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AT_type ( {0x00000147} (int) )
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AT_APPLE_property_attribute (DW_APPLE_PROPERTY_readonly, DW_APPLE_PROPERTY_nonatomic)
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</pre>
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</div>
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<p> The setter and getter method names are attached to the property using
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DW_AT_APPLE_property_setter and DW_AT_APPLE_property_getter attributes.
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</p>
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<div class="doc_code">
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<pre>
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@interface I1
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@property (setter=myOwnP3Setter:) int p3;
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-(void)myOwnP3Setter:(int)a;
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@end
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@implementation I1
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@synthesize p3;
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-(void)myOwnP3Setter:(int)a{ }
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@end
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0x000003bd: TAG_structure_type [7] *
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AT_APPLE_runtime_class( 0x10 )
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AT_name( "I1" )
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AT_decl_file( "Objc_Property.m" )
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AT_decl_line( 3 )
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0x000003f3: TAG_member [8]
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AT_name( "p3" )
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AT_APPLE_property_name(“p3”)
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AT_APPLE_property_setter(“myOwnP3Setter:”)
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AT_type( {0x00000147} ( int ) )
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</pre>
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</div>
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</div>
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<!-- *********************************************************************** -->
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<h2>
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<a name="newattributes">New DWARF Attributes</a>
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</h2>
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<!-- *********************************************************************** -->
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<div>
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<table border="1" cellspacing="0">
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<tr>
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<th width=200 >Attribute</th>
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<th width=200 >Value</th>
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<th width=200 >Classes</th>
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</tr>
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<tr>
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<td width=200 >DW_AT_APPLE_property_name</td>
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<td width=200 >0x3fe8</td>
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<td width=200 >String</td>
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</tr>
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<tr>
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<td width=200 >DW_AT_APPLE_property_getter</td>
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<td width=200 >0x3fe9</td>
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<td width=200 >String</td>
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</tr>
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<tr>
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<td width=200 >DW_AT_APPLE_property_setter</td>
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<td width=200 >0x3fea</td>
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<td width=200 >String</td>
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</tr>
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<tr>
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<td width=200 >DW_AT_APPLE_property_attribute</td>
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<td width=200 >0x3feb</td>
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<td width=200 >Constant</td>
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</tr>
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</table>
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</div>
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<!-- *********************************************************************** -->
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<h2>
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<a name="newconstants">New DWARF Constants</a>
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</h2>
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<!-- *********************************************************************** -->
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<div>
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<table border="1" cellspacing="0">
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<tr>
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<th width=200 >Name</th>
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<th width=200 >Value</th>
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</tr>
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<tr>
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<td width=200 >DW_AT_APPLE_PROPERTY_readonly</td>
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<td width=200 >0x1</td>
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</tr>
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<tr>
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<td width=200 >DW_AT_APPLE_PROPERTY_readwrite</td>
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<td width=200 >0x2</td>
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</tr>
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<tr>
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<td width=200 >DW_AT_APPLE_PROPERTY_assign</td>
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<td width=200 >0x4</td>
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</tr>
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<tr>
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<td width=200 >DW_AT_APPLE_PROPERTY_retain</td>
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<td width=200 >0x8</td>
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</tr>
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<tr>
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<td width=200 >DW_AT_APPLE_PROPERTY_copy</td>
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<td width=200 >0x10</td>
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</tr>
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<tr>
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<td width=200 >DW_AT_APPLE_PROPERTY_nonatomic</td>
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<td width=200 >0x20</td>
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</tr>
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</table>
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</div>
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<!-- *********************************************************************** -->
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<hr>
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<address>
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<a href="http://llvm.org/">LLVM Compiler Infrastructure</a><br>
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Last modified: $Date: 2011-11-14 $
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</address>
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</body>
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</html>
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