diff options
Diffstat (limited to 'docs/SourceLevelDebugging.html')
| -rw-r--r-- | docs/SourceLevelDebugging.html | 185 |
1 files changed, 137 insertions, 48 deletions
diff --git a/docs/SourceLevelDebugging.html b/docs/SourceLevelDebugging.html index f2741a2..e7eac08 100644 --- a/docs/SourceLevelDebugging.html +++ b/docs/SourceLevelDebugging.html @@ -446,7 +446,7 @@ global variables are collected by named metadata <tt>!llvm.dbg.gv</tt>.</p> i32, ;; Index into a virtual function metadata, ;; indicates which base type contains the vtable pointer for the ;; derived class - i1, ;; isArtificial + i32, ;; Flags - Artifical, Private, Protected, Explicit, Prototyped. i1, ;; isOptimized Function *,;; Pointer to LLVM function metadata, ;; Lists function template parameters @@ -459,8 +459,6 @@ global variables are collected by named metadata <tt>!llvm.dbg.gv</tt>.</p> <p>These descriptors provide debug information about functions, methods and subprograms. They provide details such as name, return types and the source location where the subprogram is defined. - All subprogram descriptors are collected by a named metadata - <tt>!llvm.dbg.sp</tt>. </p> </div> @@ -574,8 +572,9 @@ DW_ATE_unsigned_char = 8 i64, ;; Size in bits i64, ;; Alignment in bits i64, ;; Offset in bits + i32, ;; Flags to encode attributes, e.g. private metadata, ;; Reference to type derived from - metadata, ;; (optional) Name of the Objective C property assoicated with + metadata, ;; (optional) Name of the Objective C property associated with ;; Objective-C an ivar metadata, ;; (optional) Name of the Objective C property getter selector. metadata, ;; (optional) Name of the Objective C property setter selector. @@ -610,9 +609,9 @@ DW_TAG_restrict_type = 55 <p><tt>DW_TAG_typedef</tt> is used to provide a name for the derived type.</p> -<p><tt>DW_TAG_pointer_type</tt>,<tt>DW_TAG_reference_type</tt>, - <tt>DW_TAG_const_type</tt>, <tt>DW_TAG_volatile_type</tt> - and <tt>DW_TAG_restrict_type</tt> are used to qualify +<p><tt>DW_TAG_pointer_type</tt>, <tt>DW_TAG_reference_type</tt>, + <tt>DW_TAG_const_type</tt>, <tt>DW_TAG_volatile_type</tt> and + <tt>DW_TAG_restrict_type</tt> are used to qualify the <a href="#format_derived_type">derived type</a>. </p> <p><a href="#format_derived_type">Derived type</a> location can be determined @@ -833,9 +832,9 @@ DW_TAG_return_variable = 258 void %<a href="#format_common_declare">llvm.dbg.declare</a>(metadata, metadata) </pre> -<p>This intrinsic provides information about a local element (ex. variable.) The - first argument is metadata holding alloca for the variable. The - second argument is metadata containing description of the variable. </p> +<p>This intrinsic provides information about a local element (e.g., variable). The + first argument is metadata holding the alloca for the variable. The + second argument is metadata containing a description of the variable.</p> </div> <!-- ======================================================================= --> @@ -851,8 +850,8 @@ DW_TAG_return_variable = 258 <p>This intrinsic provides information when a user source variable is set to a new value. The first argument is the new value (wrapped as metadata). The second argument is the offset in the user source variable where the new value - is written. The third argument is metadata containing description of the - user source variable. </p> + is written. The third argument is metadata containing a description of the + user source variable.</p> </div> </div> @@ -1860,11 +1859,32 @@ developers inspect Objective C properties. <!-- *********************************************************************** --> <div> -<p>Objective C properties are always backed by an instance variable. The -instance variables backing properties are identified using -DW_AT_APPLE_property_name attribute. The instance variables with this -attribute may not have data location attributes. The location of instance -variables is determined by debugger only after consulting Objective C runtime. +<p>Objective C properties exist separately from class members. A property +can be defined only by "setter" and "getter" selectors, and +be calculated anew on each access. Or a property can just be a direct access +to some declared ivar. Finally it can have an ivar "automatically +synthesized" for it by the compiler, in which case the property can be +referred to in user code directly using the standard C dereference syntax as +well as through the property "dot" syntax, but there is no entry in +the @interface declaration corresponding to this ivar. +</p> +<p> +To facilitate debugging, these properties we will add a new DWARF TAG into the +DW_TAG_structure_type definition for the class to hold the description of a +given property, and a set of DWARF attributes that provide said description. +The property tag will also contain the name and declared type of the property. +</p> +<p> +If there is a related ivar, there will also be a DWARF property attribute placed +in the DW_TAG_member DIE for that ivar referring back to the property TAG for +that property. And in the case where the compiler synthesizes the ivar directly, +the compiler is expected to generate a DW_TAG_member for that ivar (with the +DW_AT_artificial set to 1), whose name will be the name used to access this +ivar directly in code, and with the property attribute pointing back to the +property it is backing. +</p> +<p> +The following examples will serve as illustration for our discussion: </p> <div class="doc_code"> @@ -1873,34 +1893,66 @@ variables is determined by debugger only after consulting Objective C runtime. int n2; } -@property p1; -@property p2; +@property int p1; +@property int p2; @end @implementation I1 @synthesize p1; @synthesize p2 = n2; @end +</pre> +</div> - -TAG_structure_type [7] * - AT_APPLE_runtime_class( 0x10 ) - AT_name( "I1" ) - AT_decl_file( "Objc_Property.m" ) - AT_decl_line( 3 ) - - TAG_member [8] - AT_name( "p1" ) - AT_APPLE_property_name(“p1”) - AT_type( {0x00000147} ( int ) ) - - TAG_member [8] - AT_name( "n2" ) - AT_APPLE_property_name(“p2”) - AT_type( {0x00000147} ( int ) ) +<p> +This produces the following DWARF (this is a "pseudo dwarfdump" output): +</p> +<div class="doc_code"> +<pre> +0x00000100: TAG_structure_type [7] * + AT_APPLE_runtime_class( 0x10 ) + AT_name( "I1" ) + AT_decl_file( "Objc_Property.m" ) + AT_decl_line( 3 ) + +0x00000110 TAG_APPLE_property + AT_name ( "p1" ) + AT_type ( {0x00000150} ( int ) ) + +0x00000120: TAG_APPLE_property + AT_name ( "p2" ) + AT_type ( {0x00000150} ( int ) ) + +0x00000130: TAG_member [8] + AT_name( "_p1" ) + AT_APPLE_property ( {0x00000110} "p1" ) + AT_type( {0x00000150} ( int ) ) + AT_artificial ( 0x1 ) + +0x00000140: TAG_member [8] + AT_name( "n2" ) + AT_APPLE_property ( {0x00000120} "p2" ) + AT_type( {0x00000150} ( int ) ) + +0x00000150: AT_type( ( int ) ) </pre> </div> +<p> Note, the current convention is that the name of the ivar for an +auto-synthesized property is the name of the property from which it derives with +an underscore prepended, as is shown in the example. +But we actually don't need to know this convention, since we are given the name +of the ivar directly. +</p> + +<p> +Also, it is common practice in ObjC to have different property declarations in +the @interface and @implementation - e.g. to provide a read-only property in +the interface,and a read-write interface in the implementation. In that case, +the compiler should emit whichever property declaration will be in force in the +current translation unit. +</p> + <p> Developers can decorate a property with attributes which are encoded using DW_AT_APPLE_property_attribute. </p> @@ -1908,11 +1960,15 @@ DW_AT_APPLE_property_attribute. <div class="doc_code"> <pre> @property (readonly, nonatomic) int pr; - - -TAG_member [8] - AT_name(“pr”) - AT_APPLE_property_name(“pr”) +</pre> +</div> +<p> +Which produces a property tag: +<p> +<div class="doc_code"> +<pre> +TAG_APPLE_property [8] + AT_name( "pr" ) AT_type ( {0x00000147} (int) ) AT_APPLE_property_attribute (DW_APPLE_PROPERTY_readonly, DW_APPLE_PROPERTY_nonatomic) </pre> @@ -1932,17 +1988,30 @@ DW_AT_APPLE_property_setter and DW_AT_APPLE_property_getter attributes. @synthesize p3; -(void)myOwnP3Setter:(int)a{ } @end +</pre> +</div> +<p> +The DWARF for this would be: +</p> +<div class="doc_code"> +<pre> 0x000003bd: TAG_structure_type [7] * AT_APPLE_runtime_class( 0x10 ) AT_name( "I1" ) AT_decl_file( "Objc_Property.m" ) AT_decl_line( 3 ) -0x000003f3: TAG_member [8] - AT_name( "p3" ) - AT_APPLE_property_name(“p3”) - AT_APPLE_property_setter(“myOwnP3Setter:”) - AT_type( {0x00000147} ( int ) ) + +0x000003cd TAG_APPLE_property + AT_name ( "p3" ) + AT_APPLE_property_setter ( "myOwnP3Setter:" ) + AT_type( {0x00000147} ( int ) ) + +0x000003f3: TAG_member [8] + AT_name( "_p3" ) + AT_type ( {0x00000147} ( int ) ) + AT_APPLE_property ( {0x000003cd} ) + AT_artificial ( 0x1 ) </pre> </div> @@ -1950,6 +2019,26 @@ DW_AT_APPLE_property_setter and DW_AT_APPLE_property_getter attributes. <!-- *********************************************************************** --> <h4> + <a name="objcpropertynewtags">New DWARF Tags</a> +</h4> +<!-- *********************************************************************** --> + +<div> +<table border="1" cellspacing="0"> + <tr> + <th width=200 >TAG</th> + <th width=200 >Value</th> + </tr> + <tr> + <td width=200 >DW_TAG_APPLE_property</td> + <td width=200 >0x4200</td> + </tr> +</table> + +</div> + +<!-- *********************************************************************** --> +<h4> <a name="objcpropertynewattributes">New DWARF Attributes</a> </h4> <!-- *********************************************************************** --> @@ -1962,9 +2051,9 @@ DW_AT_APPLE_property_setter and DW_AT_APPLE_property_getter attributes. <th width=200 >Classes</th> </tr> <tr> - <td width=200 >DW_AT_APPLE_property_name</td> - <td width=200 >0x3fe8</td> - <td width=200 >String</td> + <td width=200 >DW_AT_APPLE_property</td> + <td width=200 >0x3fed</td> + <td width=200 >Reference</td> </tr> <tr> <td width=200 >DW_AT_APPLE_property_getter</td> |