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| <h3 class="section">8.6 Method Definition</h3> |
| |
| <p>The class definition shown above declares Ameth. The C<tt>++</tt> source below |
| defines Ameth: |
| |
| <pre class="example"> int |
| baseA::Ameth(int in, char other) |
| { |
| return in; |
| }; |
| </pre> |
| <p>This method definition yields three stabs following the code of the |
| method. One stab describes the method itself and following two describe |
| its parameters. Although there is only one formal argument all methods |
| have an implicit argument which is the <code>this</code> pointer. The <code>this</code> |
| pointer is a pointer to the object on which the method was called. Note |
| that the method name is mangled to encode the class name and argument |
| types. Name mangling is described in the <span class="sc">arm</span> (<cite>The Annotated |
| C++ Reference Manual</cite>, by Ellis and Stroustrup, <span class="sc">isbn</span> |
| 0-201-51459-1); <samp><span class="file">gpcompare.texi</span></samp> in Cygnus GCC distributions |
| describes the differences between GNU mangling and <span class="sc">arm</span> |
| mangling. |
| <!-- FIXME: Use @xref, especially if this is generally installed in the --> |
| <!-- info tree. --> |
| <!-- FIXME: This information should be in a net release, either of GCC or --> |
| <!-- GDB. But gpcompare.texi doesn't seem to be in the FSF GCC. --> |
| |
| <pre class="example"> .stabs "name:symbol_descriptor(global function)return_type(int)", |
| N_FUN, NIL, NIL, code_addr_of_method_start |
| |
| .stabs "Ameth__5baseAic:F1",36,0,0,_Ameth__5baseAic |
| </pre> |
| <p>Here is the stab for the <code>this</code> pointer implicit argument. The |
| name of the <code>this</code> pointer is always <code>this</code>. Type 19, the |
| <code>this</code> pointer is defined as a pointer to type 20, <code>baseA</code>, |
| but a stab defining <code>baseA</code> has not yet been emitted. Since the |
| compiler knows it will be emitted shortly, here it just outputs a cross |
| reference to the undefined symbol, by prefixing the symbol name with |
| ‘<samp><span class="samp">xs</span></samp>’. |
| |
| <pre class="example"> .stabs "name:sym_desc(register param)type_def(19)= |
| type_desc(ptr to)type_ref(baseA)= |
| type_desc(cross-reference to)baseA:",N_RSYM,NIL,NIL,register_number |
| |
| .stabs "this:P19=*20=xsbaseA:",64,0,0,8 |
| </pre> |
| <p>The stab for the explicit integer argument looks just like a parameter |
| to a C function. The last field of the stab is the offset from the |
| argument pointer, which in most systems is the same as the frame |
| pointer. |
| |
| <pre class="example"> .stabs "name:sym_desc(value parameter)type_ref(int)", |
| N_PSYM,NIL,NIL,offset_from_arg_ptr |
| |
| .stabs "in:p1",160,0,0,72 |
| </pre> |
| <p><< The examples that follow are based on A1.C >> |
| |
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