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| <title>STABS: Simple Classes</title> |
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| <a name="Simple-Classes"></a> |
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| Next: <a href="Class-Instance.html#Class-Instance" accesskey="n" rel="next">Class Instance</a>, Previous: <a href="Basic-Cplusplus-Types.html#Basic-Cplusplus-Types" accesskey="p" rel="prev">Basic Cplusplus Types</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> |
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| <a name="Simple-Class-Definition"></a> |
| <h3 class="section">8.4 Simple Class Definition</h3> |
| |
| <p>The stabs describing C<tt>++</tt> language features are an extension of the |
| stabs describing C. Stabs representing C<tt>++</tt> class types elaborate |
| extensively on the stab format used to describe structure types in C. |
| Stabs representing class type variables look just like stabs |
| representing C language variables. |
| </p> |
| <p>Consider the following very simple class definition. |
| </p> |
| <div class="example"> |
| <pre class="example">class baseA { |
| public: |
| int Adat; |
| int Ameth(int in, char other); |
| }; |
| </pre></div> |
| |
| <p>The class <code>baseA</code> is represented by two stabs. The first stab describes |
| the class as a structure type. The second stab describes a structure |
| tag of the class type. Both stabs are of stab type <code>N_LSYM</code>. Since the |
| stab is not located between an <code>N_FUN</code> and an <code>N_LBRAC</code> stab this indicates |
| that the class is defined at file scope. If it were, then the <code>N_LSYM</code> |
| would signify a local variable. |
| </p> |
| <p>A stab describing a C<tt>++</tt> class type is similar in format to a stab |
| describing a C struct, with each class member shown as a field in the |
| structure. The part of the struct format describing fields is |
| expanded to include extra information relevant to C<tt>++</tt> class members. |
| In addition, if the class has multiple base classes or virtual |
| functions the struct format outside of the field parts is also |
| augmented. |
| </p> |
| <p>In this simple example the field part of the C<tt>++</tt> class stab |
| representing member data looks just like the field part of a C struct |
| stab. The section on protections describes how its format is |
| sometimes extended for member data. |
| </p> |
| <p>The field part of a C<tt>++</tt> class stab representing a member function |
| differs substantially from the field part of a C struct stab. It |
| still begins with ‘<samp>name:</samp>’ but then goes on to define a new type number |
| for the member function, describe its return type, its argument types, |
| its protection level, any qualifiers applied to the method definition, |
| and whether the method is virtual or not. If the method is virtual |
| then the method description goes on to give the vtable index of the |
| method, and the type number of the first base class defining the |
| method. |
| </p> |
| <p>When the field name is a method name it is followed by two colons rather |
| than one. This is followed by a new type definition for the method. |
| This is a number followed by an equal sign and the type of the method. |
| Normally this will be a type declared using the ‘<samp>#</samp>’ type |
| descriptor; see <a href="Method-Type-Descriptor.html#Method-Type-Descriptor">Method Type Descriptor</a>; static member functions |
| are declared using the ‘<samp>f</samp>’ type descriptor instead; see |
| <a href="Function-Types.html#Function-Types">Function Types</a>. |
| </p> |
| <p>The format of an overloaded operator method name differs from that of |
| other methods. It is ‘<samp>op$::<var>operator-name</var>.</samp>’ where |
| <var>operator-name</var> is the operator name such as ‘<samp>+</samp>’ or ‘<samp>+=</samp>’. |
| The name ends with a period, and any characters except the period can |
| occur in the <var>operator-name</var> string. |
| </p> |
| <p>The next part of the method description represents the arguments to the |
| method, preceded by a colon and ending with a semi-colon. The types of |
| the arguments are expressed in the same way argument types are expressed |
| in C<tt>++</tt> name mangling. In this example an <code>int</code> and a <code>char</code> |
| map to ‘<samp>ic</samp>’. |
| </p> |
| <p>This is followed by a number, a letter, and an asterisk or period, |
| followed by another semicolon. The number indicates the protections |
| that apply to the member function. Here the 2 means public. The |
| letter encodes any qualifier applied to the method definition. In |
| this case, ‘<samp>A</samp>’ means that it is a normal function definition. The dot |
| shows that the method is not virtual. The sections that follow |
| elaborate further on these fields and describe the additional |
| information present for virtual methods. |
| </p> |
| |
| <div class="display"> |
| <pre class="display">.stabs "class_name:sym_desc(type)type_def(20)=type_desc(struct)struct_bytes(4) |
| field_name(Adat):type(int),bit_offset(0),field_bits(32); |
| |
| method_name(Ameth)::type_def(21)=type_desc(method)return_type(int); |
| :arg_types(int char); |
| protection(public)qualifier(normal)virtual(no);;" |
| N_LSYM,NIL,NIL,NIL |
| </pre></div> |
| |
| <div class="smallexample"> |
| <pre class="smallexample">.stabs "baseA:t20=s4Adat:1,0,32;Ameth::21=##1;:ic;2A.;;",128,0,0,0 |
| |
| .stabs "class_name:sym_desc(struct tag)",N_LSYM,NIL,NIL,NIL |
| |
| .stabs "baseA:T20",128,0,0,0 |
| </pre></div> |
| |
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