You cannot select more than 25 topics
Topics must start with a letter or number, can include dashes ('-') and can be up to 35 characters long.
179 lines
7.4 KiB
HTML
179 lines
7.4 KiB
HTML
4 years ago
|
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
|
||
|
|
<html>
|
||
|
|
<!-- Copyright (C) 1992-2019 Free Software Foundation, Inc.
|
||
|
|
Contributed by Cygnus Support. Written by Julia Menapace, Jim Kingdon,
|
||
|
|
and David MacKenzie.
|
||
|
|
|
||
|
|
Permission is granted to copy, distribute and/or modify this document
|
||
|
|
under the terms of the GNU Free Documentation License, Version 1.3 or
|
||
|
|
any later version published by the Free Software Foundation; with no
|
||
|
|
Invariant Sections, with no Front-Cover Texts, and with no Back-Cover
|
||
|
|
Texts. A copy of the license is included in the section entitled "GNU
|
||
|
|
Free Documentation License". -->
|
||
|
|
<!-- Created by GNU Texinfo 6.4, http://www.gnu.org/software/texinfo/ -->
|
||
|
|
<head>
|
||
|
|
<title>Inheritance (STABS)</title>
|
||
|
|
|
||
|
|
<meta name="description" content="Inheritance (STABS)">
|
||
|
|
<meta name="keywords" content="Inheritance (STABS)">
|
||
|
|
<meta name="resource-type" content="document">
|
||
|
|
<meta name="distribution" content="global">
|
||
|
|
<meta name="Generator" content="makeinfo">
|
||
|
|
<meta http-equiv="Content-Type" content="text/html; charset=utf-8">
|
||
|
|
<link href="index.html#Top" rel="start" title="Top">
|
||
|
|
<link href="Symbol-Types-Index.html#Symbol-Types-Index" rel="index" title="Symbol Types Index">
|
||
|
|
<link href="index.html#SEC_Contents" rel="contents" title="Table of Contents">
|
||
|
|
<link href="Cplusplus.html#Cplusplus" rel="up" title="Cplusplus">
|
||
|
|
<link href="Virtual-Base-Classes.html#Virtual-Base-Classes" rel="next" title="Virtual Base Classes">
|
||
|
|
<link href="Virtual-Methods.html#Virtual-Methods" rel="prev" title="Virtual Methods">
|
||
|
|
<style type="text/css">
|
||
|
|
<!--
|
||
|
|
a.summary-letter {text-decoration: none}
|
||
|
|
blockquote.indentedblock {margin-right: 0em}
|
||
|
|
blockquote.smallindentedblock {margin-right: 0em; font-size: smaller}
|
||
|
|
blockquote.smallquotation {font-size: smaller}
|
||
|
|
div.display {margin-left: 3.2em}
|
||
|
|
div.example {margin-left: 3.2em}
|
||
|
|
div.lisp {margin-left: 3.2em}
|
||
|
|
div.smalldisplay {margin-left: 3.2em}
|
||
|
|
div.smallexample {margin-left: 3.2em}
|
||
|
|
div.smalllisp {margin-left: 3.2em}
|
||
|
|
kbd {font-style: oblique}
|
||
|
|
pre.display {font-family: inherit}
|
||
|
|
pre.format {font-family: inherit}
|
||
|
|
pre.menu-comment {font-family: serif}
|
||
|
|
pre.menu-preformatted {font-family: serif}
|
||
|
|
pre.smalldisplay {font-family: inherit; font-size: smaller}
|
||
|
|
pre.smallexample {font-size: smaller}
|
||
|
|
pre.smallformat {font-family: inherit; font-size: smaller}
|
||
|
|
pre.smalllisp {font-size: smaller}
|
||
|
|
span.nolinebreak {white-space: nowrap}
|
||
|
|
span.roman {font-family: initial; font-weight: normal}
|
||
|
|
span.sansserif {font-family: sans-serif; font-weight: normal}
|
||
|
|
ul.no-bullet {list-style: none}
|
||
|
|
-->
|
||
|
|
</style>
|
||
|
|
|
||
|
|
|
||
|
|
</head>
|
||
|
|
|
||
|
|
<body lang="en">
|
||
|
|
<a name="Inheritance"></a>
|
||
|
|
<div class="header">
|
||
|
|
<p>
|
||
|
|
Next: <a href="Virtual-Base-Classes.html#Virtual-Base-Classes" accesskey="n" rel="next">Virtual Base Classes</a>, Previous: <a href="Virtual-Methods.html#Virtual-Methods" accesskey="p" rel="prev">Virtual Methods</a>, Up: <a href="Cplusplus.html#Cplusplus" accesskey="u" rel="up">Cplusplus</a> [<a href="index.html#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="Symbol-Types-Index.html#Symbol-Types-Index" title="Index" rel="index">Index</a>]</p>
|
||
|
|
</div>
|
||
|
|
<hr>
|
||
|
|
<a name="Inheritance-1"></a>
|
||
|
|
<h3 class="section">8.12 Inheritance</h3>
|
||
|
|
|
||
|
|
<p>Stabs describing C<tt>++</tt> derived classes include additional sections that
|
||
|
|
describe the inheritance hierarchy of the class. A derived class stab
|
||
|
|
also encodes the number of base classes. For each base class it tells
|
||
|
|
if the base class is virtual or not, and if the inheritance is private
|
||
|
|
or public. It also gives the offset into the object of the portion of
|
||
|
|
the object corresponding to each base class.
|
||
|
|
</p>
|
||
|
|
<p>This additional information is embedded in the class stab following the
|
||
|
|
number of bytes in the struct. First the number of base classes
|
||
|
|
appears bracketed by an exclamation point and a comma.
|
||
|
|
</p>
|
||
|
|
<p>Then for each base type there repeats a series: a virtual character, a
|
||
|
|
visibility character, a number, a comma, another number, and a
|
||
|
|
semi-colon.
|
||
|
|
</p>
|
||
|
|
<p>The virtual character is ‘<samp>1</samp>’ if the base class is virtual and
|
||
|
|
‘<samp>0</samp>’ if not. The visibility character is ‘<samp>2</samp>’ if the derivation
|
||
|
|
is public, ‘<samp>1</samp>’ if it is protected, and ‘<samp>0</samp>’ if it is private.
|
||
|
|
Debuggers should ignore virtual or visibility characters they do not
|
||
|
|
recognize, and assume a reasonable default (such as public and
|
||
|
|
non-virtual) (GDB 4.11 does not, but this should be fixed in the next
|
||
|
|
GDB release).
|
||
|
|
</p>
|
||
|
|
<p>The number following the virtual and visibility characters is the offset
|
||
|
|
from the start of the object to the part of the object pertaining to the
|
||
|
|
base class.
|
||
|
|
</p>
|
||
|
|
<p>After the comma, the second number is a type_descriptor for the base
|
||
|
|
type. Finally a semi-colon ends the series, which repeats for each
|
||
|
|
base class.
|
||
|
|
</p>
|
||
|
|
<p>The source below defines three base classes <code>A</code>, <code>B</code>, and
|
||
|
|
<code>C</code> and the derived class <code>D</code>.
|
||
|
|
</p>
|
||
|
|
|
||
|
|
<div class="example">
|
||
|
|
<pre class="example">class A {
|
||
|
|
public:
|
||
|
|
int Adat;
|
||
|
|
virtual int A_virt (int arg) { return arg; };
|
||
|
|
};
|
||
|
|
|
||
|
|
class B {
|
||
|
|
public:
|
||
|
|
int B_dat;
|
||
|
|
virtual int B_virt (int arg) {return arg; };
|
||
|
|
};
|
||
|
|
|
||
|
|
class C {
|
||
|
|
public:
|
||
|
|
int Cdat;
|
||
|
|
virtual int C_virt (int arg) {return arg; };
|
||
|
|
};
|
||
|
|
|
||
|
|
class D : A, virtual B, public C {
|
||
|
|
public:
|
||
|
|
int Ddat;
|
||
|
|
virtual int A_virt (int arg ) { return arg+1; };
|
||
|
|
virtual int B_virt (int arg) { return arg+2; };
|
||
|
|
virtual int C_virt (int arg) { return arg+3; };
|
||
|
|
virtual int D_virt (int arg) { return arg; };
|
||
|
|
};
|
||
|
|
</pre></div>
|
||
|
|
|
||
|
|
<p>Class stabs similar to the ones described earlier are generated for
|
||
|
|
each base class.
|
||
|
|
</p>
|
||
|
|
<div class="smallexample">
|
||
|
|
<pre class="smallexample">.stabs "A:T20=s8Adat:1,0,32;$vf20:21=*22=ar1;0;1;17,32;
|
||
|
|
A_virt::23=##1;:i;2A*-2147483647;20;;;~%20;",128,0,0,0
|
||
|
|
|
||
|
|
.stabs "B:Tt25=s8Bdat:1,0,32;$vf25:21,32;B_virt::26=##1;
|
||
|
|
:i;2A*-2147483647;25;;;~%25;",128,0,0,0
|
||
|
|
|
||
|
|
.stabs "C:Tt28=s8Cdat:1,0,32;$vf28:21,32;C_virt::29=##1;
|
||
|
|
:i;2A*-2147483647;28;;;~%28;",128,0,0,0
|
||
|
|
</pre></div>
|
||
|
|
|
||
|
|
<p>In the stab describing derived class <code>D</code> below, the information about
|
||
|
|
the derivation of this class is encoded as follows.
|
||
|
|
</p>
|
||
|
|
<div class="display">
|
||
|
|
<pre class="display">.stabs "derived_class_name:symbol_descriptors(struct tag&type)=
|
||
|
|
type_descriptor(struct)struct_bytes(32)!num_bases(3),
|
||
|
|
base_virtual(no)inheritance_public(no)base_offset(0),
|
||
|
|
base_class_type_ref(A);
|
||
|
|
base_virtual(yes)inheritance_public(no)base_offset(NIL),
|
||
|
|
base_class_type_ref(B);
|
||
|
|
base_virtual(no)inheritance_public(yes)base_offset(64),
|
||
|
|
base_class_type_ref(C); …
|
||
|
|
</pre></div>
|
||
|
|
|
||
|
|
<div class="smallexample">
|
||
|
|
<pre class="smallexample">.stabs "D:Tt31=s32!3,000,20;100,25;0264,28;$vb25:24,128;Ddat:
|
||
|
|
1,160,32;A_virt::32=##1;:i;2A*-2147483647;20;;B_virt:
|
||
|
|
:32:i;2A*-2147483647;25;;C_virt::32:i;2A*-2147483647;
|
||
|
|
28;;D_virt::32:i;2A*-2147483646;31;;;~%20;",128,0,0,0
|
||
|
|
</pre></div>
|
||
|
|
|
||
|
|
<hr>
|
||
|
|
<div class="header">
|
||
|
|
<p>
|
||
|
|
Next: <a href="Virtual-Base-Classes.html#Virtual-Base-Classes" accesskey="n" rel="next">Virtual Base Classes</a>, Previous: <a href="Virtual-Methods.html#Virtual-Methods" accesskey="p" rel="prev">Virtual Methods</a>, Up: <a href="Cplusplus.html#Cplusplus" accesskey="u" rel="up">Cplusplus</a> [<a href="index.html#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="Symbol-Types-Index.html#Symbol-Types-Index" title="Index" rel="index">Index</a>]</p>
|
||
|
|
</div>
|
||
|
|
|
||
|
|
|
||
|
|
|
||
|
|
</body>
|
||
|
|
</html>
|