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| author | alk3pInjection <webmaster@raspii.tech> | 2024-02-04 16:16:35 +0800 |
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| committer | alk3pInjection <webmaster@raspii.tech> | 2024-02-04 16:16:35 +0800 |
| commit | abdaadbcae30fe0c9a66c7516798279fdfd97750 (patch) | |
| tree | 00a54a6e25601e43876d03c1a4a12a749d4a914c /share/doc/gdb/Data.html | |
https://developer.arm.com/downloads/-/arm-gnu-toolchain-downloads
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diff --git a/share/doc/gdb/Data.html b/share/doc/gdb/Data.html new file mode 100644 index 0000000..af34cc2 --- /dev/null +++ b/share/doc/gdb/Data.html @@ -0,0 +1,439 @@ +<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd"> +<html> +<!-- Copyright (C) 1988-2023 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 5.1, http://www.gnu.org/software/texinfo/ --> +<head> +<title>Debugging with GDB: Data</title> + +<meta name="description" content="Debugging with GDB: Data"> +<meta name="keywords" content="Debugging with GDB: Data"> +<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="index.html#Top" rel="up" title="Top"> +<link href="Expressions.html#Expressions" rel="next" title="Expressions"> +<link href="Disable-Reading-Source.html#Disable-Reading-Source" rel="previous" title="Disable Reading Source"> +<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="Data"></a> +<div class="header"> +<p> +Next: <a href="Optimized-Code.html#Optimized-Code" accesskey="n" rel="next">Optimized Code</a>, Previous: <a href="Source.html#Source" accesskey="p" rel="previous">Source</a>, Up: <a href="index.html#Top" accesskey="u" rel="up">Top</a> [<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="Examining-Data"></a> +<h2 class="chapter">10 Examining Data</h2> + +<a name="index-printing-data"></a> +<a name="index-examining-data"></a> +<a name="index-print"></a> +<a name="index-inspect"></a> +<p>The usual way to examine data in your program is with the <code>print</code> +command (abbreviated <code>p</code>), or its synonym <code>inspect</code>. It +evaluates and prints the value of an expression of the language your +program is written in (see <a href="Languages.html#Languages">Using <small>GDB</small> with +Different Languages</a>). It may also print the expression using a +Python-based pretty-printer (see <a href="Pretty-Printing.html#Pretty-Printing">Pretty Printing</a>). +</p> +<dl compact="compact"> +<dt><code>print [[<var>options</var>] --] <var>expr</var></code></dt> +<dt><code>print [[<var>options</var>] --] /<var>f</var> <var>expr</var></code></dt> +<dd><p><var>expr</var> is an expression (in the source language). By default the +value of <var>expr</var> is printed in a format appropriate to its data type; +you can choose a different format by specifying ‘<samp>/<var>f</var></samp>’, where +<var>f</var> is a letter specifying the format; see <a href="Output-Formats.html#Output-Formats">Output +Formats</a>. +</p> +<a name="print-options"></a><p>The <code>print</code> command supports a number of options that allow +overriding relevant global print settings as set by <code>set print</code> +subcommands: +</p> +<dl compact="compact"> +<dt><code>-address [<code>on</code>|<code>off</code>]</code></dt> +<dd><p>Set printing of addresses. +Related setting: <a href="Print-Settings.html#set-print-address">set print address</a>. +</p> +</dd> +<dt><code>-array [<code>on</code>|<code>off</code>]</code></dt> +<dd><p>Pretty formatting of arrays. +Related setting: <a href="Print-Settings.html#set-print-array">set print array</a>. +</p> +</dd> +<dt><code>-array-indexes [<code>on</code>|<code>off</code>]</code></dt> +<dd><p>Set printing of array indexes. +Related setting: <a href="Print-Settings.html#set-print-array_002dindexes">set print array-indexes</a>. +</p> +</dd> +<dt><code>-elements <var>number-of-elements</var>|<code>unlimited</code></code></dt> +<dd><p>Set limit on string chars or array elements to print. The value +<code>unlimited</code> causes there to be no limit. Related setting: +<a href="Print-Settings.html#set-print-elements">set print elements</a>. +</p> +</dd> +<dt><code>-max-depth <var>depth</var>|<code>unlimited</code></code></dt> +<dd><p>Set the threshold after which nested structures are replaced with +ellipsis. Related setting: <a href="Print-Settings.html#set-print-max_002ddepth">set print max-depth</a>. +</p> +</dd> +<dt><code>-nibbles [<code>on</code>|<code>off</code>]</code></dt> +<dd><p>Set whether to print binary values in groups of four bits, known +as “nibbles”. See <a href="Print-Settings.html#set-print-nibbles">set print nibbles</a>. +</p> +</dd> +<dt><code>-memory-tag-violations [<code>on</code>|<code>off</code>]</code></dt> +<dd><p>Set printing of additional information about memory tag violations. +See <a href="Print-Settings.html#set-print-memory_002dtag_002dviolations">set print memory-tag-violations</a>. +</p> +</dd> +<dt><code>-null-stop [<code>on</code>|<code>off</code>]</code></dt> +<dd><p>Set printing of char arrays to stop at first null char. Related +setting: <a href="Print-Settings.html#set-print-null_002dstop">set print null-stop</a>. +</p> +</dd> +<dt><code>-object [<code>on</code>|<code>off</code>]</code></dt> +<dd><p>Set printing C<tt>++</tt> virtual function tables. Related setting: +<a href="Print-Settings.html#set-print-object">set print object</a>. +</p> +</dd> +<dt><code>-pretty [<code>on</code>|<code>off</code>]</code></dt> +<dd><p>Set pretty formatting of structures. Related setting: <a href="Print-Settings.html#set-print-pretty">set print pretty</a>. +</p> +</dd> +<dt><code>-raw-values [<code>on</code>|<code>off</code>]</code></dt> +<dd><p>Set whether to print values in raw form, bypassing any +pretty-printers for that value. Related setting: <a href="Print-Settings.html#set-print-raw_002dvalues">set print raw-values</a>. +</p> +</dd> +<dt><code>-repeats <var>number-of-repeats</var>|<code>unlimited</code></code></dt> +<dd><p>Set threshold for repeated print elements. <code>unlimited</code> causes +all elements to be individually printed. Related setting: <a href="Print-Settings.html#set-print-repeats">set print repeats</a>. +</p> +</dd> +<dt><code>-static-members [<code>on</code>|<code>off</code>]</code></dt> +<dd><p>Set printing C<tt>++</tt> static members. Related setting: <a href="Print-Settings.html#set-print-static_002dmembers">set print static-members</a>. +</p> +</dd> +<dt><code>-symbol [<code>on</code>|<code>off</code>]</code></dt> +<dd><p>Set printing of symbol names when printing pointers. Related setting: +<a href="Print-Settings.html#set-print-symbol">set print symbol</a>. +</p> +</dd> +<dt><code>-union [<code>on</code>|<code>off</code>]</code></dt> +<dd><p>Set printing of unions interior to structures. Related setting: +<a href="Print-Settings.html#set-print-union">set print union</a>. +</p> +</dd> +<dt><code>-vtbl [<code>on</code>|<code>off</code>]</code></dt> +<dd><p>Set printing of C++ virtual function tables. Related setting: +<a href="Print-Settings.html#set-print-vtbl">set print vtbl</a>. +</p></dd> +</dl> + +<p>Because the <code>print</code> command accepts arbitrary expressions which +may look like options (including abbreviations), if you specify any +command option, then you must use a double dash (<code>--</code>) to mark +the end of option processing. +</p> +<p>For example, this prints the value of the <code>-p</code> expression: +</p> +<div class="smallexample"> +<pre class="smallexample">(gdb) print -p +</pre></div> + +<p>While this repeats the last value in the value history (see below) +with the <code>-pretty</code> option in effect: +</p> +<div class="smallexample"> +<pre class="smallexample">(gdb) print -p -- +</pre></div> + +<p>Here is an example including both on option and an expression: +</p> +<div class="smallexample"> +<pre class="smallexample">(gdb) print -pretty -- *myptr +$1 = { + next = 0x0, + flags = { + sweet = 1, + sour = 1 + }, + meat = 0x54 "Pork" +} +</pre></div> + +</dd> +<dt><code>print [<var>options</var>]</code></dt> +<dt><code>print [<var>options</var>] /<var>f</var></code></dt> +<dd><a name="index-reprint-the-last-value"></a> +<p>If you omit <var>expr</var>, <small>GDB</small> displays the last value again (from the +<em>value history</em>; see <a href="Value-History.html#Value-History">Value History</a>). This allows you to +conveniently inspect the same value in an alternative format. +</p></dd> +</dl> + +<p>If the architecture supports memory tagging, the <code>print</code> command will +display pointer/memory tag mismatches if what is being printed is a pointer +or reference type. See <a href="Memory-Tagging.html#Memory-Tagging">Memory Tagging</a>. +</p> +<p>A more low-level way of examining data is with the <code>x</code> command. +It examines data in memory at a specified address and prints it in a +specified format. See <a href="Memory.html#Memory">Examining Memory</a>. +</p> +<p>If you are interested in information about types, or about how the +fields of a struct or a class are declared, use the <code>ptype <var>expr</var></code> +command rather than <code>print</code>. See <a href="Symbols.html#Symbols">Examining the Symbol +Table</a>. +</p> +<a name="index-exploring-hierarchical-data-structures"></a> +<a name="index-explore"></a> +<p>Another way of examining values of expressions and type information is +through the Python extension command <code>explore</code> (available only if +the <small>GDB</small> build is configured with <code>--with-python</code>). It +offers an interactive way to start at the highest level (or, the most +abstract level) of the data type of an expression (or, the data type +itself) and explore all the way down to leaf scalar values/fields +embedded in the higher level data types. +</p> +<dl compact="compact"> +<dt><code>explore <var>arg</var></code></dt> +<dd><p><var>arg</var> is either an expression (in the source language), or a type +visible in the current context of the program being debugged. +</p></dd> +</dl> + +<p>The working of the <code>explore</code> command can be illustrated with an +example. If a data type <code>struct ComplexStruct</code> is defined in your +C program as +</p> +<div class="smallexample"> +<pre class="smallexample">struct SimpleStruct +{ + int i; + double d; +}; + +struct ComplexStruct +{ + struct SimpleStruct *ss_p; + int arr[10]; +}; +</pre></div> + +<p>followed by variable declarations as +</p> +<div class="smallexample"> +<pre class="smallexample">struct SimpleStruct ss = { 10, 1.11 }; +struct ComplexStruct cs = { &ss, { 0, 1, 2, 3, 4, 5, 6, 7, 8, 9 } }; +</pre></div> + +<p>then, the value of the variable <code>cs</code> can be explored using the +<code>explore</code> command as follows. +</p> +<div class="smallexample"> +<pre class="smallexample">(gdb) explore cs +The value of `cs' is a struct/class of type `struct ComplexStruct' with +the following fields: + + ss_p = <Enter 0 to explore this field of type `struct SimpleStruct *'> + arr = <Enter 1 to explore this field of type `int [10]'> + +Enter the field number of choice: +</pre></div> + +<p>Since the fields of <code>cs</code> are not scalar values, you are being +prompted to chose the field you want to explore. Let’s say you choose +the field <code>ss_p</code> by entering <code>0</code>. Then, since this field is a +pointer, you will be asked if it is pointing to a single value. From +the declaration of <code>cs</code> above, it is indeed pointing to a single +value, hence you enter <code>y</code>. If you enter <code>n</code>, then you will +be asked if it were pointing to an array of values, in which case this +field will be explored as if it were an array. +</p> +<div class="smallexample"> +<pre class="smallexample">`cs.ss_p' is a pointer to a value of type `struct SimpleStruct' +Continue exploring it as a pointer to a single value [y/n]: y +The value of `*(cs.ss_p)' is a struct/class of type `struct +SimpleStruct' with the following fields: + + i = 10 .. (Value of type `int') + d = 1.1100000000000001 .. (Value of type `double') + +Press enter to return to parent value: +</pre></div> + +<p>If the field <code>arr</code> of <code>cs</code> was chosen for exploration by +entering <code>1</code> earlier, then since it is as array, you will be +prompted to enter the index of the element in the array that you want +to explore. +</p> +<div class="smallexample"> +<pre class="smallexample">`cs.arr' is an array of `int'. +Enter the index of the element you want to explore in `cs.arr': 5 + +`(cs.arr)[5]' is a scalar value of type `int'. + +(cs.arr)[5] = 4 + +Press enter to return to parent value: +</pre></div> + +<p>In general, at any stage of exploration, you can go deeper towards the +leaf values by responding to the prompts appropriately, or hit the +return key to return to the enclosing data structure (the <i>higher</i> +level data structure). +</p> +<p>Similar to exploring values, you can use the <code>explore</code> command to +explore types. Instead of specifying a value (which is typically a +variable name or an expression valid in the current context of the +program being debugged), you specify a type name. If you consider the +same example as above, your can explore the type +<code>struct ComplexStruct</code> by passing the argument +<code>struct ComplexStruct</code> to the <code>explore</code> command. +</p> +<div class="smallexample"> +<pre class="smallexample">(gdb) explore struct ComplexStruct +</pre></div> + +<p>By responding to the prompts appropriately in the subsequent interactive +session, you can explore the type <code>struct ComplexStruct</code> in a +manner similar to how the value <code>cs</code> was explored in the above +example. +</p> +<p>The <code>explore</code> command also has two sub-commands, +<code>explore value</code> and <code>explore type</code>. The former sub-command is +a way to explicitly specify that value exploration of the argument is +being invoked, while the latter is a way to explicitly specify that type +exploration of the argument is being invoked. +</p> +<dl compact="compact"> +<dt><code>explore value <var>expr</var></code></dt> +<dd><a name="index-explore-value"></a> +<p>This sub-command of <code>explore</code> explores the value of the +expression <var>expr</var> (if <var>expr</var> is an expression valid in the +current context of the program being debugged). The behavior of this +command is identical to that of the behavior of the <code>explore</code> +command being passed the argument <var>expr</var>. +</p> +</dd> +<dt><code>explore type <var>arg</var></code></dt> +<dd><a name="index-explore-type"></a> +<p>This sub-command of <code>explore</code> explores the type of <var>arg</var> (if +<var>arg</var> is a type visible in the current context of program being +debugged), or the type of the value/expression <var>arg</var> (if <var>arg</var> +is an expression valid in the current context of the program being +debugged). If <var>arg</var> is a type, then the behavior of this command is +identical to that of the <code>explore</code> command being passed the +argument <var>arg</var>. If <var>arg</var> is an expression, then the behavior of +this command will be identical to that of the <code>explore</code> command +being passed the type of <var>arg</var> as the argument. +</p></dd> +</dl> + +<table class="menu" border="0" cellspacing="0"> +<tr><td align="left" valign="top">• <a href="Expressions.html#Expressions" accesskey="1">Expressions</a>:</td><td> </td><td align="left" valign="top">Expressions +</td></tr> +<tr><td align="left" valign="top">• <a href="Ambiguous-Expressions.html#Ambiguous-Expressions" accesskey="2">Ambiguous Expressions</a>:</td><td> </td><td align="left" valign="top">Ambiguous Expressions +</td></tr> +<tr><td align="left" valign="top">• <a href="Variables.html#Variables" accesskey="3">Variables</a>:</td><td> </td><td align="left" valign="top">Program variables +</td></tr> +<tr><td align="left" valign="top">• <a href="Arrays.html#Arrays" accesskey="4">Arrays</a>:</td><td> </td><td align="left" valign="top">Artificial arrays +</td></tr> +<tr><td align="left" valign="top">• <a href="Output-Formats.html#Output-Formats" accesskey="5">Output Formats</a>:</td><td> </td><td align="left" valign="top">Output formats +</td></tr> +<tr><td align="left" valign="top">• <a href="Memory.html#Memory" accesskey="6">Memory</a>:</td><td> </td><td align="left" valign="top">Examining memory +</td></tr> +<tr><td align="left" valign="top">• <a href="Memory-Tagging.html#Memory-Tagging" accesskey="7">Memory Tagging</a>:</td><td> </td><td align="left" valign="top">Memory Tagging +</td></tr> +<tr><td align="left" valign="top">• <a href="Auto-Display.html#Auto-Display" accesskey="8">Auto Display</a>:</td><td> </td><td align="left" valign="top">Automatic display +</td></tr> +<tr><td align="left" valign="top">• <a href="Print-Settings.html#Print-Settings" accesskey="9">Print Settings</a>:</td><td> </td><td align="left" valign="top">Print settings +</td></tr> +<tr><td align="left" valign="top">• <a href="Pretty-Printing.html#Pretty-Printing">Pretty Printing</a>:</td><td> </td><td align="left" valign="top">Python pretty printing +</td></tr> +<tr><td align="left" valign="top">• <a href="Value-History.html#Value-History">Value History</a>:</td><td> </td><td align="left" valign="top">Value history +</td></tr> +<tr><td align="left" valign="top">• <a href="Convenience-Vars.html#Convenience-Vars">Convenience Vars</a>:</td><td> </td><td align="left" valign="top">Convenience variables +</td></tr> +<tr><td align="left" valign="top">• <a href="Convenience-Funs.html#Convenience-Funs">Convenience Funs</a>:</td><td> </td><td align="left" valign="top">Convenience functions +</td></tr> +<tr><td align="left" valign="top">• <a href="Registers.html#Registers">Registers</a>:</td><td> </td><td align="left" valign="top">Registers +</td></tr> +<tr><td align="left" valign="top">• <a href="Floating-Point-Hardware.html#Floating-Point-Hardware">Floating Point Hardware</a>:</td><td> </td><td align="left" valign="top">Floating point hardware +</td></tr> +<tr><td align="left" valign="top">• <a href="Vector-Unit.html#Vector-Unit">Vector Unit</a>:</td><td> </td><td align="left" valign="top">Vector Unit +</td></tr> +<tr><td align="left" valign="top">• <a href="OS-Information.html#OS-Information">OS Information</a>:</td><td> </td><td align="left" valign="top">Auxiliary data provided by operating system +</td></tr> +<tr><td align="left" valign="top">• <a href="Memory-Region-Attributes.html#Memory-Region-Attributes">Memory Region Attributes</a>:</td><td> </td><td align="left" valign="top">Memory region attributes +</td></tr> +<tr><td align="left" valign="top">• <a href="Dump_002fRestore-Files.html#Dump_002fRestore-Files">Dump/Restore Files</a>:</td><td> </td><td align="left" valign="top">Copy between memory and a file +</td></tr> +<tr><td align="left" valign="top">• <a href="Core-File-Generation.html#Core-File-Generation">Core File Generation</a>:</td><td> </td><td align="left" valign="top">Cause a program dump its core +</td></tr> +<tr><td align="left" valign="top">• <a href="Character-Sets.html#Character-Sets">Character Sets</a>:</td><td> </td><td align="left" valign="top">Debugging programs that use a different + character set than GDB does +</td></tr> +<tr><td align="left" valign="top">• <a href="Caching-Target-Data.html#Caching-Target-Data">Caching Target Data</a>:</td><td> </td><td align="left" valign="top">Data caching for targets +</td></tr> +<tr><td align="left" valign="top">• <a href="Searching-Memory.html#Searching-Memory">Searching Memory</a>:</td><td> </td><td align="left" valign="top">Searching memory for a sequence of bytes +</td></tr> +<tr><td align="left" valign="top">• <a href="Value-Sizes.html#Value-Sizes">Value Sizes</a>:</td><td> </td><td align="left" valign="top">Managing memory allocated for values +</td></tr> +</table> + +<hr> +<div class="header"> +<p> +Next: <a href="Optimized-Code.html#Optimized-Code" accesskey="n" rel="next">Optimized Code</a>, Previous: <a href="Source.html#Source" accesskey="p" rel="previous">Source</a>, Up: <a href="index.html#Top" accesskey="u" rel="up">Top</a> [<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> |