106 lines
4.8 KiB
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106 lines
4.8 KiB
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<html lang="en">
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<head>
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<title>Methods - STABS</title>
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<meta name="description" content="STABS">
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<link title="Top" rel="start" href="index.html#Top">
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<link rel="up" href="Cplusplus.html#Cplusplus" title="Cplusplus">
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<link rel="prev" href="Class-Instance.html#Class-Instance" title="Class Instance">
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<link rel="next" href="Method-Type-Descriptor.html#Method-Type-Descriptor" title="Method Type Descriptor">
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<!--
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Copyright (C) 1992-2019 Free Software Foundation, Inc.
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Contributed by Cygnus Support. Written by Julia Menapace, Jim Kingdon,
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and David MacKenzie.
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Permission is granted to copy, distribute and/or modify this document
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under the terms of the GNU Free Documentation License, Version 1.3 or
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any later version published by the Free Software Foundation; with no
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Invariant Sections, with no Front-Cover Texts, and with no Back-Cover
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<div class="node">
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<a name="Methods"></a>
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<p>
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Next: <a rel="next" accesskey="n" href="Method-Type-Descriptor.html#Method-Type-Descriptor">Method Type Descriptor</a>,
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Previous: <a rel="previous" accesskey="p" href="Class-Instance.html#Class-Instance">Class Instance</a>,
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Up: <a rel="up" accesskey="u" href="Cplusplus.html#Cplusplus">Cplusplus</a>
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<hr>
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</div>
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<h3 class="section">8.6 Method Definition</h3>
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<p>The class definition shown above declares Ameth. The C<tt>++</tt> source below
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defines Ameth:
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<pre class="example"> int
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baseA::Ameth(int in, char other)
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{
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return in;
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};
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</pre>
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<p>This method definition yields three stabs following the code of the
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method. One stab describes the method itself and following two describe
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its parameters. Although there is only one formal argument all methods
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have an implicit argument which is the <code>this</code> pointer. The <code>this</code>
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pointer is a pointer to the object on which the method was called. Note
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that the method name is mangled to encode the class name and argument
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types. Name mangling is described in the <span class="sc">arm</span> (<cite>The Annotated
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C++ Reference Manual</cite>, by Ellis and Stroustrup, <span class="sc">isbn</span>
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0-201-51459-1); <samp><span class="file">gpcompare.texi</span></samp> in Cygnus GCC distributions
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describes the differences between GNU mangling and <span class="sc">arm</span>
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mangling.
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<!-- FIXME: Use @xref, especially if this is generally installed in the -->
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<!-- info tree. -->
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<!-- FIXME: This information should be in a net release, either of GCC or -->
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<!-- GDB. But gpcompare.texi doesn't seem to be in the FSF GCC. -->
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<pre class="example"> .stabs "name:symbol_descriptor(global function)return_type(int)",
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N_FUN, NIL, NIL, code_addr_of_method_start
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.stabs "Ameth__5baseAic:F1",36,0,0,_Ameth__5baseAic
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</pre>
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<p>Here is the stab for the <code>this</code> pointer implicit argument. The
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name of the <code>this</code> pointer is always <code>this</code>. Type 19, the
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<code>this</code> pointer is defined as a pointer to type 20, <code>baseA</code>,
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but a stab defining <code>baseA</code> has not yet been emitted. Since the
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compiler knows it will be emitted shortly, here it just outputs a cross
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reference to the undefined symbol, by prefixing the symbol name with
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‘<samp><span class="samp">xs</span></samp>’.
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<pre class="example"> .stabs "name:sym_desc(register param)type_def(19)=
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type_desc(ptr to)type_ref(baseA)=
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type_desc(cross-reference to)baseA:",N_RSYM,NIL,NIL,register_number
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.stabs "this:P19=*20=xsbaseA:",64,0,0,8
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</pre>
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<p>The stab for the explicit integer argument looks just like a parameter
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to a C function. The last field of the stab is the offset from the
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argument pointer, which in most systems is the same as the frame
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pointer.
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<pre class="example"> .stabs "name:sym_desc(value parameter)type_ref(int)",
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N_PSYM,NIL,NIL,offset_from_arg_ptr
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.stabs "in:p1",160,0,0,72
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</pre>
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<p><< The examples that follow are based on A1.C >>
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</body></html>
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