aarch64-linux-gnu-5.1/share/doc/gdb/Symbols-In-Python.html

<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<!-- Copyright (C) 1988-2015 Free Software Foundation, Inc.

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 the
Invariant Sections being "Free Software" and "Free Software Needs
Free Documentation", with the Front-Cover Texts being "A GNU Manual,"
and with the Back-Cover Texts as in (a) below.

(a) The FSF's Back-Cover Text is: "You are free to copy and modify
this GNU Manual.  Buying copies from GNU Press supports the FSF in
developing GNU and promoting software freedom." -->
<!-- Created by GNU Texinfo 5.2, http://www.gnu.org/software/texinfo/ -->
<head>
<title>Debugging with GDB: Symbols In Python</title>

<meta name="description" content="Debugging with GDB: Symbols In Python">
<meta name="keywords" content="Debugging with GDB: Symbols In Python">
<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="Concept-Index.html#Concept-Index" rel="index" title="Concept Index">
<link href="index.html#SEC_Contents" rel="contents" title="Table of Contents">
<link href="Python-API.html#Python-API" rel="up" title="Python API">
<link href="Symbol-Tables-In-Python.html#Symbol-Tables-In-Python" rel="next" title="Symbol Tables In Python">
<link href="Blocks-In-Python.html#Blocks-In-Python" rel="prev" title="Blocks In Python">
<style type="text/css">
<!--
a.summary-letter {text-decoration: none}
blockquote.smallquotation {font-size: smaller}
div.display {margin-left: 3.2em}
div.example {margin-left: 3.2em}
div.indentedblock {margin-left: 3.2em}
div.lisp {margin-left: 3.2em}
div.smalldisplay {margin-left: 3.2em}
div.smallexample {margin-left: 3.2em}
div.smallindentedblock {margin-left: 3.2em; font-size: smaller}
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.nocodebreak {white-space:nowrap}
span.nolinebreak {white-space:nowrap}
span.roman {font-family:serif; font-weight:normal}
span.sansserif {font-family:sans-serif; font-weight:normal}
ul.no-bullet {list-style: none}
-->
</style>


</head>

<body lang="en" bgcolor="#FFFFFF" text="#000000" link="#0000FF" vlink="#800080" alink="#FF0000">
<a name="Symbols-In-Python"></a>
<div class="header">
<p>
Next: <a href="Symbol-Tables-In-Python.html#Symbol-Tables-In-Python" accesskey="n" rel="next">Symbol Tables In Python</a>, Previous: <a href="Blocks-In-Python.html#Blocks-In-Python" accesskey="p" rel="prev">Blocks In Python</a>, Up: <a href="Python-API.html#Python-API" accesskey="u" rel="up">Python API</a> &nbsp; [<a href="index.html#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="Concept-Index.html#Concept-Index" title="Index" rel="index">Index</a>]</p>
</div>
<hr>
<a name="Python-representation-of-Symbols_002e"></a>
<h4 class="subsubsection">23.2.2.26 Python representation of Symbols.</h4>

<a name="index-symbols-in-python"></a>
<a name="index-gdb_002eSymbol"></a>

<p><small>GDB</small> represents every variable, function and type as an
entry in a symbol table.  See <a href="Symbols.html#Symbols">Examining the Symbol Table</a>.
Similarly, Python represents these symbols in <small>GDB</small> with the
<code>gdb.Symbol</code> object.
</p>
<p>The following symbol-related functions are available in the <code>gdb</code>
module:
</p>
<a name="index-gdb_002elookup_005fsymbol"></a>
<dl>
<dt><a name="index-gdb_002elookup_005fsymbol-1"></a>Function: <strong>gdb.lookup_symbol</strong> <em>(name <span class="roman">[</span>, block <span class="roman">[</span>, domain<span class="roman">]]</span>)</em></dt>
<dd><p>This function searches for a symbol by name.  The search scope can be
restricted to the parameters defined in the optional domain and block
arguments.
</p>
<p><var>name</var> is the name of the symbol.  It must be a string.  The
optional <var>block</var> argument restricts the search to symbols visible
in that <var>block</var>.  The <var>block</var> argument must be a
<code>gdb.Block</code> object.  If omitted, the block for the current frame
is used.  The optional <var>domain</var> argument restricts
the search to the domain type.  The <var>domain</var> argument must be a
domain constant defined in the <code>gdb</code> module and described later
in this chapter.
</p>
<p>The result is a tuple of two elements.
The first element is a <code>gdb.Symbol</code> object or <code>None</code> if the symbol
is not found.
If the symbol is found, the second element is <code>True</code> if the symbol
is a field of a method&rsquo;s object (e.g., <code>this</code> in C<tt>++</tt>),
otherwise it is <code>False</code>.
If the symbol is not found, the second element is <code>False</code>.
</p></dd></dl>

<a name="index-gdb_002elookup_005fglobal_005fsymbol"></a>
<dl>
<dt><a name="index-gdb_002elookup_005fglobal_005fsymbol-1"></a>Function: <strong>gdb.lookup_global_symbol</strong> <em>(name <span class="roman">[</span>, domain<span class="roman">]</span>)</em></dt>
<dd><p>This function searches for a global symbol by name.
The search scope can be restricted to by the domain argument.
</p>
<p><var>name</var> is the name of the symbol.  It must be a string.
The optional <var>domain</var> argument restricts the search to the domain type.
The <var>domain</var> argument must be a domain constant defined in the <code>gdb</code>
module and described later in this chapter.
</p>
<p>The result is a <code>gdb.Symbol</code> object or <code>None</code> if the symbol
is not found.
</p></dd></dl>

<p>A <code>gdb.Symbol</code> object has the following attributes:
</p>
<dl>
<dt><a name="index-Symbol_002etype"></a>Variable: <strong>Symbol.type</strong></dt>
<dd><p>The type of the symbol or <code>None</code> if no type is recorded.
This attribute is represented as a <code>gdb.Type</code> object.
See <a href="Types-In-Python.html#Types-In-Python">Types In Python</a>.  This attribute is not writable.
</p></dd></dl>

<dl>
<dt><a name="index-Symbol_002esymtab"></a>Variable: <strong>Symbol.symtab</strong></dt>
<dd><p>The symbol table in which the symbol appears.  This attribute is
represented as a <code>gdb.Symtab</code> object.  See <a href="Symbol-Tables-In-Python.html#Symbol-Tables-In-Python">Symbol Tables In Python</a>.  This attribute is not writable.
</p></dd></dl>

<dl>
<dt><a name="index-Symbol_002eline"></a>Variable: <strong>Symbol.line</strong></dt>
<dd><p>The line number in the source code at which the symbol was defined.
This is an integer.
</p></dd></dl>

<dl>
<dt><a name="index-Symbol_002ename"></a>Variable: <strong>Symbol.name</strong></dt>
<dd><p>The name of the symbol as a string.  This attribute is not writable.
</p></dd></dl>

<dl>
<dt><a name="index-Symbol_002elinkage_005fname"></a>Variable: <strong>Symbol.linkage_name</strong></dt>
<dd><p>The name of the symbol, as used by the linker (i.e., may be mangled).
This attribute is not writable.
</p></dd></dl>

<dl>
<dt><a name="index-Symbol_002eprint_005fname"></a>Variable: <strong>Symbol.print_name</strong></dt>
<dd><p>The name of the symbol in a form suitable for output.  This is either
<code>name</code> or <code>linkage_name</code>, depending on whether the user
asked <small>GDB</small> to display demangled or mangled names.
</p></dd></dl>

<dl>
<dt><a name="index-Symbol_002eaddr_005fclass"></a>Variable: <strong>Symbol.addr_class</strong></dt>
<dd><p>The address class of the symbol.  This classifies how to find the value
of a symbol.  Each address class is a constant defined in the
<code>gdb</code> module and described later in this chapter.
</p></dd></dl>

<dl>
<dt><a name="index-Symbol_002eneeds_005fframe"></a>Variable: <strong>Symbol.needs_frame</strong></dt>
<dd><p>This is <code>True</code> if evaluating this symbol&rsquo;s value requires a frame
(see <a href="Frames-In-Python.html#Frames-In-Python">Frames In Python</a>) and <code>False</code> otherwise.  Typically,
local variables will require a frame, but other symbols will not.
</p></dd></dl>

<dl>
<dt><a name="index-Symbol_002eis_005fargument"></a>Variable: <strong>Symbol.is_argument</strong></dt>
<dd><p><code>True</code> if the symbol is an argument of a function.
</p></dd></dl>

<dl>
<dt><a name="index-Symbol_002eis_005fconstant"></a>Variable: <strong>Symbol.is_constant</strong></dt>
<dd><p><code>True</code> if the symbol is a constant.
</p></dd></dl>

<dl>
<dt><a name="index-Symbol_002eis_005ffunction"></a>Variable: <strong>Symbol.is_function</strong></dt>
<dd><p><code>True</code> if the symbol is a function or a method.
</p></dd></dl>

<dl>
<dt><a name="index-Symbol_002eis_005fvariable"></a>Variable: <strong>Symbol.is_variable</strong></dt>
<dd><p><code>True</code> if the symbol is a variable.
</p></dd></dl>

<p>A <code>gdb.Symbol</code> object has the following methods:
</p>
<dl>
<dt><a name="index-Symbol_002eis_005fvalid"></a>Function: <strong>Symbol.is_valid</strong> <em>()</em></dt>
<dd><p>Returns <code>True</code> if the <code>gdb.Symbol</code> object is valid,
<code>False</code> if not.  A <code>gdb.Symbol</code> object can become invalid if
the symbol it refers to does not exist in <small>GDB</small> any longer.
All other <code>gdb.Symbol</code> methods will throw an exception if it is
invalid at the time the method is called.
</p></dd></dl>

<dl>
<dt><a name="index-Symbol_002evalue"></a>Function: <strong>Symbol.value</strong> <em>(<span class="roman">[</span>frame<span class="roman">]</span>)</em></dt>
<dd><p>Compute the value of the symbol, as a <code>gdb.Value</code>.  For
functions, this computes the address of the function, cast to the
appropriate type.  If the symbol requires a frame in order to compute
its value, then <var>frame</var> must be given.  If <var>frame</var> is not
given, or if <var>frame</var> is invalid, then this method will throw an
exception.
</p></dd></dl>

<p>The available domain categories in <code>gdb.Symbol</code> are represented
as constants in the <code>gdb</code> module:
</p>
<dl compact="compact">
<dd><a name="index-SYMBOL_005fUNDEF_005fDOMAIN"></a>
</dd>
<dt><code>gdb.SYMBOL_UNDEF_DOMAIN</code>
<a name="index-gdb_002eSYMBOL_005fUNDEF_005fDOMAIN"></a>
</dt>
<dd><p>This is used when a domain has not been discovered or none of the
following domains apply.  This usually indicates an error either
in the symbol information or in <small>GDB</small>&rsquo;s handling of symbols.
</p>
<a name="index-SYMBOL_005fVAR_005fDOMAIN"></a>
</dd>
<dt><code>gdb.SYMBOL_VAR_DOMAIN</code>
<a name="index-gdb_002eSYMBOL_005fVAR_005fDOMAIN"></a>
</dt>
<dd><p>This domain contains variables, function names, typedef names and enum
type values.
</p>
<a name="index-SYMBOL_005fSTRUCT_005fDOMAIN"></a>
</dd>
<dt><code>gdb.SYMBOL_STRUCT_DOMAIN</code>
<a name="index-gdb_002eSYMBOL_005fSTRUCT_005fDOMAIN"></a>
</dt>
<dd><p>This domain holds struct, union and enum type names.
</p>
<a name="index-SYMBOL_005fLABEL_005fDOMAIN"></a>
</dd>
<dt><code>gdb.SYMBOL_LABEL_DOMAIN</code>
<a name="index-gdb_002eSYMBOL_005fLABEL_005fDOMAIN"></a>
</dt>
<dd><p>This domain contains names of labels (for gotos).
</p>
<a name="index-SYMBOL_005fVARIABLES_005fDOMAIN"></a>
</dd>
<dt><code>gdb.SYMBOL_VARIABLES_DOMAIN</code>
<a name="index-gdb_002eSYMBOL_005fVARIABLES_005fDOMAIN"></a>
</dt>
<dd><p>This domain holds a subset of the <code>SYMBOLS_VAR_DOMAIN</code>; it
contains everything minus functions and types.
</p>
<a name="index-SYMBOL_005fFUNCTIONS_005fDOMAIN"></a>
</dd>
<dt><code>gdb.SYMBOL_FUNCTION_DOMAIN</code>
<a name="index-gdb_002eSYMBOL_005fFUNCTION_005fDOMAIN"></a>
</dt>
<dd><p>This domain contains all functions.
</p>
<a name="index-SYMBOL_005fTYPES_005fDOMAIN"></a>
</dd>
<dt><code>gdb.SYMBOL_TYPES_DOMAIN</code>
<a name="index-gdb_002eSYMBOL_005fTYPES_005fDOMAIN"></a>
</dt>
<dd><p>This domain contains all types.
</p></dd>
</dl>

<p>The available address class categories in <code>gdb.Symbol</code> are represented
as constants in the <code>gdb</code> module:
</p>
<dl compact="compact">
<dd><a name="index-SYMBOL_005fLOC_005fUNDEF"></a>
</dd>
<dt><code>gdb.SYMBOL_LOC_UNDEF</code>
<a name="index-gdb_002eSYMBOL_005fLOC_005fUNDEF"></a>
</dt>
<dd><p>If this is returned by address class, it indicates an error either in
the symbol information or in <small>GDB</small>&rsquo;s handling of symbols.
</p>
<a name="index-SYMBOL_005fLOC_005fCONST"></a>
</dd>
<dt><code>gdb.SYMBOL_LOC_CONST</code>
<a name="index-gdb_002eSYMBOL_005fLOC_005fCONST"></a>
</dt>
<dd><p>Value is constant int.
</p>
<a name="index-SYMBOL_005fLOC_005fSTATIC"></a>
</dd>
<dt><code>gdb.SYMBOL_LOC_STATIC</code>
<a name="index-gdb_002eSYMBOL_005fLOC_005fSTATIC"></a>
</dt>
<dd><p>Value is at a fixed address.
</p>
<a name="index-SYMBOL_005fLOC_005fREGISTER"></a>
</dd>
<dt><code>gdb.SYMBOL_LOC_REGISTER</code>
<a name="index-gdb_002eSYMBOL_005fLOC_005fREGISTER"></a>
</dt>
<dd><p>Value is in a register.
</p>
<a name="index-SYMBOL_005fLOC_005fARG"></a>
</dd>
<dt><code>gdb.SYMBOL_LOC_ARG</code>
<a name="index-gdb_002eSYMBOL_005fLOC_005fARG"></a>
</dt>
<dd><p>Value is an argument.  This value is at the offset stored within the
symbol inside the frame&rsquo;s argument list.
</p>
<a name="index-SYMBOL_005fLOC_005fREF_005fARG"></a>
</dd>
<dt><code>gdb.SYMBOL_LOC_REF_ARG</code>
<a name="index-gdb_002eSYMBOL_005fLOC_005fREF_005fARG"></a>
</dt>
<dd><p>Value address is stored in the frame&rsquo;s argument list.  Just like
<code>LOC_ARG</code> except that the value&rsquo;s address is stored at the
offset, not the value itself.
</p>
<a name="index-SYMBOL_005fLOC_005fREGPARM_005fADDR"></a>
</dd>
<dt><code>gdb.SYMBOL_LOC_REGPARM_ADDR</code>
<a name="index-gdb_002eSYMBOL_005fLOC_005fREGPARM_005fADDR"></a>
</dt>
<dd><p>Value is a specified register.  Just like <code>LOC_REGISTER</code> except
the register holds the address of the argument instead of the argument
itself.
</p>
<a name="index-SYMBOL_005fLOC_005fLOCAL"></a>
</dd>
<dt><code>gdb.SYMBOL_LOC_LOCAL</code>
<a name="index-gdb_002eSYMBOL_005fLOC_005fLOCAL"></a>
</dt>
<dd><p>Value is a local variable.
</p>
<a name="index-SYMBOL_005fLOC_005fTYPEDEF"></a>
</dd>
<dt><code>gdb.SYMBOL_LOC_TYPEDEF</code>
<a name="index-gdb_002eSYMBOL_005fLOC_005fTYPEDEF"></a>
</dt>
<dd><p>Value not used.  Symbols in the domain <code>SYMBOL_STRUCT_DOMAIN</code> all
have this class.
</p>
<a name="index-SYMBOL_005fLOC_005fBLOCK"></a>
</dd>
<dt><code>gdb.SYMBOL_LOC_BLOCK</code>
<a name="index-gdb_002eSYMBOL_005fLOC_005fBLOCK"></a>
</dt>
<dd><p>Value is a block.
</p>
<a name="index-SYMBOL_005fLOC_005fCONST_005fBYTES"></a>
</dd>
<dt><code>gdb.SYMBOL_LOC_CONST_BYTES</code>
<a name="index-gdb_002eSYMBOL_005fLOC_005fCONST_005fBYTES"></a>
</dt>
<dd><p>Value is a byte-sequence.
</p>
<a name="index-SYMBOL_005fLOC_005fUNRESOLVED"></a>
</dd>
<dt><code>gdb.SYMBOL_LOC_UNRESOLVED</code>
<a name="index-gdb_002eSYMBOL_005fLOC_005fUNRESOLVED"></a>
</dt>
<dd><p>Value is at a fixed address, but the address of the variable has to be
determined from the minimal symbol table whenever the variable is
referenced.
</p>
<a name="index-SYMBOL_005fLOC_005fOPTIMIZED_005fOUT"></a>
</dd>
<dt><code>gdb.SYMBOL_LOC_OPTIMIZED_OUT</code>
<a name="index-gdb_002eSYMBOL_005fLOC_005fOPTIMIZED_005fOUT"></a>
</dt>
<dd><p>The value does not actually exist in the program.
</p>
<a name="index-SYMBOL_005fLOC_005fCOMPUTED"></a>
</dd>
<dt><code>gdb.SYMBOL_LOC_COMPUTED</code>
<a name="index-gdb_002eSYMBOL_005fLOC_005fCOMPUTED"></a>
</dt>
<dd><p>The value&rsquo;s address is a computed location.
</p></dd>
</dl>

<hr>
<div class="header">
<p>
Next: <a href="Symbol-Tables-In-Python.html#Symbol-Tables-In-Python" accesskey="n" rel="next">Symbol Tables In Python</a>, Previous: <a href="Blocks-In-Python.html#Blocks-In-Python" accesskey="p" rel="prev">Blocks In Python</a>, Up: <a href="Python-API.html#Python-API" accesskey="u" rel="up">Python API</a> &nbsp; [<a href="index.html#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="Concept-Index.html#Concept-Index" title="Index" rel="index">Index</a>]</p>
</div>



</body>
</html>