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<h3 class="section">27.16 <span class="sc">gdb/mi</span> Data Manipulation</h3>

<p><a name="index-data-manipulation_002c-in-_0040sc_007bgdb_002fmi_007d-3046"></a><a name="index-g_t_0040sc_007bgdb_002fmi_007d_002c-data-manipulation-3047"></a>This section describes the <span class="sc">gdb/mi</span> commands that manipulate data:
examine memory and registers, evaluate expressions, etc.

   <p>For details about what an addressable memory unit is,
see <a href="addressable-memory-unit.html#addressable-memory-unit">addressable memory unit</a>.

<!-- REMOVED FROM THE INTERFACE. -->
<!-- @subheading -data-assign -->
<!-- Change the value of a program variable. Plenty of side effects. -->
<!-- @subsubheading GDB Command -->
<!-- set variable -->
<!-- @subsubheading Example -->
<!-- N.A. -->
<h4 class="subheading">The <code>-data-disassemble</code> Command</h4>

<p><a name="index-g_t_002ddata_002ddisassemble-3048"></a>

<h5 class="subsubheading">Synopsis</h5>

<pre class="smallexample">      -data-disassemble
         [ -s <var>start-addr</var> -e <var>end-addr</var> ]
       | [ -a <var>addr</var> ]
       | [ -f <var>filename</var> -l <var>linenum</var> [ -n <var>lines</var> ] ]
       -- <var>mode</var>
</pre>
<p class="noindent">Where:

     <dl>
<dt>&lsquo;<samp><var>start-addr</var></samp>&rsquo;<dd>is the beginning address (or <code>$pc</code>)
<br><dt>&lsquo;<samp><var>end-addr</var></samp>&rsquo;<dd>is the end address
<br><dt>&lsquo;<samp><var>addr</var></samp>&rsquo;<dd>is an address anywhere within (or the name of) the function to
disassemble.  If an address is specified, the whole function
surrounding that address will be disassembled.  If a name is
specified, the whole function with that name will be disassembled. 
<br><dt>&lsquo;<samp><var>filename</var></samp>&rsquo;<dd>is the name of the file to disassemble
<br><dt>&lsquo;<samp><var>linenum</var></samp>&rsquo;<dd>is the line number to disassemble around
<br><dt>&lsquo;<samp><var>lines</var></samp>&rsquo;<dd>is the number of disassembly lines to be produced.  If it is -1,
the whole function will be disassembled, in case no <var>end-addr</var> is
specified.  If <var>end-addr</var> is specified as a non-zero value, and
<var>lines</var> is lower than the number of disassembly lines between
<var>start-addr</var> and <var>end-addr</var>, only <var>lines</var> lines are
displayed; if <var>lines</var> is higher than the number of lines between
<var>start-addr</var> and <var>end-addr</var>, only the lines up to <var>end-addr</var>
are displayed. 
<br><dt>&lsquo;<samp><var>mode</var></samp>&rsquo;<dd>is one of:
          <ul>
<li>0 disassembly only
<li>1 mixed source and disassembly (deprecated)
<li>2 disassembly with raw opcodes
<li>3 mixed source and disassembly with raw opcodes (deprecated)
<li>4 mixed source and disassembly
<li>5 mixed source and disassembly with raw opcodes
</ul>

     <p>Modes 1 and 3 are deprecated.  The output is &ldquo;source centric&rdquo;
which hasn't proved useful in practice. 
See <a href="Machine-Code.html#Machine-Code">Machine Code</a>, for a discussion of the difference between
<code>/m</code> and <code>/s</code> output of the <code>disassemble</code> command. 
</dl>

<h5 class="subsubheading">Result</h5>

<p>The result of the <code>-data-disassemble</code> command will be a list named
&lsquo;<samp><span class="samp">asm_insns</span></samp>&rsquo;, the contents of this list depend on the <var>mode</var>
used with the <code>-data-disassemble</code> command.

   <p>For modes 0 and 2 the &lsquo;<samp><span class="samp">asm_insns</span></samp>&rsquo; list contains tuples with the
following fields:

     <dl>
<dt><code>address</code><dd>The address at which this instruction was disassembled.

     <br><dt><code>func-name</code><dd>The name of the function this instruction is within.

     <br><dt><code>offset</code><dd>The decimal offset in bytes from the start of &lsquo;<samp><span class="samp">func-name</span></samp>&rsquo;.

     <br><dt><code>inst</code><dd>The text disassembly for this &lsquo;<samp><span class="samp">address</span></samp>&rsquo;.

     <br><dt><code>opcodes</code><dd>This field is only present for modes 2, 3 and 5.  This contains the raw opcode
bytes for the &lsquo;<samp><span class="samp">inst</span></samp>&rsquo; field.

   </dl>

   <p>For modes 1, 3, 4 and 5 the &lsquo;<samp><span class="samp">asm_insns</span></samp>&rsquo; list contains tuples named
&lsquo;<samp><span class="samp">src_and_asm_line</span></samp>&rsquo;, each of which has the following fields:

     <dl>
<dt><code>line</code><dd>The line number within &lsquo;<samp><span class="samp">file</span></samp>&rsquo;.

     <br><dt><code>file</code><dd>The file name from the compilation unit.  This might be an absolute
file name or a relative file name depending on the compile command
used.

     <br><dt><code>fullname</code><dd>Absolute file name of &lsquo;<samp><span class="samp">file</span></samp>&rsquo;.  It is converted to a canonical form
using the source file search path
(see <a href="Source-Path.html#Source-Path">Specifying Source Directories</a>)
and after resolving all the symbolic links.

     <p>If the source file is not found this field will contain the path as
present in the debug information.

     <br><dt><code>line_asm_insn</code><dd>This is a list of tuples containing the disassembly for &lsquo;<samp><span class="samp">line</span></samp>&rsquo; in
&lsquo;<samp><span class="samp">file</span></samp>&rsquo;.  The fields of each tuple are the same as for
<code>-data-disassemble</code> in <var>mode</var> 0 and 2, so &lsquo;<samp><span class="samp">address</span></samp>&rsquo;,
&lsquo;<samp><span class="samp">func-name</span></samp>&rsquo;, &lsquo;<samp><span class="samp">offset</span></samp>&rsquo;, &lsquo;<samp><span class="samp">inst</span></samp>&rsquo;, and optionally
&lsquo;<samp><span class="samp">opcodes</span></samp>&rsquo;.

   </dl>

   <p>Note that whatever included in the &lsquo;<samp><span class="samp">inst</span></samp>&rsquo; field, is not
manipulated directly by <span class="sc">gdb/mi</span>, i.e., it is not possible to
adjust its format.

<h5 class="subsubheading"><span class="sc">gdb</span> Command</h5>

<p>The corresponding <span class="sc">gdb</span> command is &lsquo;<samp><span class="samp">disassemble</span></samp>&rsquo;.

<h5 class="subsubheading">Example</h5>

<p>Disassemble from the current value of <code>$pc</code> to <code>$pc + 20</code>:

<pre class="smallexample">     (gdb)
     -data-disassemble -s $pc -e "$pc + 20" -- 0
     ^done,
     asm_insns=[
     {address="0x000107c0",func-name="main",offset="4",
     inst="mov  2, %o0"},
     {address="0x000107c4",func-name="main",offset="8",
     inst="sethi  %hi(0x11800), %o2"},
     {address="0x000107c8",func-name="main",offset="12",
     inst="or  %o2, 0x140, %o1\t! 0x11940 &lt;_lib_version+8&gt;"},
     {address="0x000107cc",func-name="main",offset="16",
     inst="sethi  %hi(0x11800), %o2"},
     {address="0x000107d0",func-name="main",offset="20",
     inst="or  %o2, 0x168, %o4\t! 0x11968 &lt;_lib_version+48&gt;"}]
     (gdb)
</pre>
   <p>Disassemble the whole <code>main</code> function.  Line 32 is part of
<code>main</code>.

<pre class="smallexample">     -data-disassemble -f basics.c -l 32 -- 0
     ^done,asm_insns=[
     {address="0x000107bc",func-name="main",offset="0",
     inst="save  %sp, -112, %sp"},
     {address="0x000107c0",func-name="main",offset="4",
     inst="mov   2, %o0"},
     {address="0x000107c4",func-name="main",offset="8",
     inst="sethi %hi(0x11800), %o2"},
     [...]
     {address="0x0001081c",func-name="main",offset="96",inst="ret "},
     {address="0x00010820",func-name="main",offset="100",inst="restore "}]
     (gdb)
</pre>
   <p>Disassemble 3 instructions from the start of <code>main</code>:

<pre class="smallexample">     (gdb)
     -data-disassemble -f basics.c -l 32 -n 3 -- 0
     ^done,asm_insns=[
     {address="0x000107bc",func-name="main",offset="0",
     inst="save  %sp, -112, %sp"},
     {address="0x000107c0",func-name="main",offset="4",
     inst="mov  2, %o0"},
     {address="0x000107c4",func-name="main",offset="8",
     inst="sethi  %hi(0x11800), %o2"}]
     (gdb)
</pre>
   <p>Disassemble 3 instructions from the start of <code>main</code> in mixed mode:

<pre class="smallexample">     (gdb)
     -data-disassemble -f basics.c -l 32 -n 3 -- 1
     ^done,asm_insns=[
     src_and_asm_line={line="31",
     file="../../../src/gdb/testsuite/gdb.mi/basics.c",
     fullname="/absolute/path/to/src/gdb/testsuite/gdb.mi/basics.c",
     line_asm_insn=[{address="0x000107bc",
     func-name="main",offset="0",inst="save  %sp, -112, %sp"}]},
     src_and_asm_line={line="32",
     file="../../../src/gdb/testsuite/gdb.mi/basics.c",
     fullname="/absolute/path/to/src/gdb/testsuite/gdb.mi/basics.c",
     line_asm_insn=[{address="0x000107c0",
     func-name="main",offset="4",inst="mov  2, %o0"},
     {address="0x000107c4",func-name="main",offset="8",
     inst="sethi  %hi(0x11800), %o2"}]}]
     (gdb)
</pre>
   <h4 class="subheading">The <code>-data-evaluate-expression</code> Command</h4>

<p><a name="index-g_t_002ddata_002devaluate_002dexpression-3049"></a>

<h5 class="subsubheading">Synopsis</h5>

<pre class="smallexample">      -data-evaluate-expression <var>expr</var>
</pre>
   <p>Evaluate <var>expr</var> as an expression.  The expression could contain an
inferior function call.  The function call will execute synchronously. 
If the expression contains spaces, it must be enclosed in double quotes.

<h5 class="subsubheading"><span class="sc">gdb</span> Command</h5>

<p>The corresponding <span class="sc">gdb</span> commands are &lsquo;<samp><span class="samp">print</span></samp>&rsquo;, &lsquo;<samp><span class="samp">output</span></samp>&rsquo;, and
&lsquo;<samp><span class="samp">call</span></samp>&rsquo;.  In <code>gdbtk</code> only, there's a corresponding
&lsquo;<samp><span class="samp">gdb_eval</span></samp>&rsquo; command.

<h5 class="subsubheading">Example</h5>

<p>In the following example, the numbers that precede the commands are the
<dfn>tokens</dfn> described in <a href="GDB_002fMI-Command-Syntax.html#GDB_002fMI-Command-Syntax"><span class="sc">gdb/mi</span> Command Syntax</a>.  Notice how <span class="sc">gdb/mi</span> returns the same tokens in its
output.

<pre class="smallexample">     211-data-evaluate-expression A
     211^done,value="1"
     (gdb)
     311-data-evaluate-expression &amp;A
     311^done,value="0xefffeb7c"
     (gdb)
     411-data-evaluate-expression A+3
     411^done,value="4"
     (gdb)
     511-data-evaluate-expression "A + 3"
     511^done,value="4"
     (gdb)
</pre>
   <h4 class="subheading">The <code>-data-list-changed-registers</code> Command</h4>

<p><a name="index-g_t_002ddata_002dlist_002dchanged_002dregisters-3050"></a>

<h5 class="subsubheading">Synopsis</h5>

<pre class="smallexample">      -data-list-changed-registers
</pre>
   <p>Display a list of the registers that have changed.

<h5 class="subsubheading"><span class="sc">gdb</span> Command</h5>

<p><span class="sc">gdb</span> doesn't have a direct analog for this command; <code>gdbtk</code>
has the corresponding command &lsquo;<samp><span class="samp">gdb_changed_register_list</span></samp>&rsquo;.

<h5 class="subsubheading">Example</h5>

<p>On a PPC MBX board:

<pre class="smallexample">     (gdb)
     -exec-continue
     ^running
     
     (gdb)
     *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",frame={
     func="main",args=[],file="try.c",fullname="/home/foo/bar/try.c",
     line="5",arch="powerpc"}
     (gdb)
     -data-list-changed-registers
     ^done,changed-registers=["0","1","2","4","5","6","7","8","9",
     "10","11","13","14","15","16","17","18","19","20","21","22","23",
     "24","25","26","27","28","30","31","64","65","66","67","69"]
     (gdb)
</pre>
   <h4 class="subheading">The <code>-data-list-register-names</code> Command</h4>

<p><a name="index-g_t_002ddata_002dlist_002dregister_002dnames-3051"></a>

<h5 class="subsubheading">Synopsis</h5>

<pre class="smallexample">      -data-list-register-names [ ( <var>regno</var> )+ ]
</pre>
   <p>Show a list of register names for the current target.  If no arguments
are given, it shows a list of the names of all the registers.  If
integer numbers are given as arguments, it will print a list of the
names of the registers corresponding to the arguments.  To ensure
consistency between a register name and its number, the output list may
include empty register names.

<h5 class="subsubheading"><span class="sc">gdb</span> Command</h5>

<p><span class="sc">gdb</span> does not have a command which corresponds to
&lsquo;<samp><span class="samp">-data-list-register-names</span></samp>&rsquo;.  In <code>gdbtk</code> there is a
corresponding command &lsquo;<samp><span class="samp">gdb_regnames</span></samp>&rsquo;.

<h5 class="subsubheading">Example</h5>

<p>For the PPC MBX board:
<pre class="smallexample">     (gdb)
     -data-list-register-names
     ^done,register-names=["r0","r1","r2","r3","r4","r5","r6","r7",
     "r8","r9","r10","r11","r12","r13","r14","r15","r16","r17","r18",
     "r19","r20","r21","r22","r23","r24","r25","r26","r27","r28","r29",
     "r30","r31","f0","f1","f2","f3","f4","f5","f6","f7","f8","f9",
     "f10","f11","f12","f13","f14","f15","f16","f17","f18","f19","f20",
     "f21","f22","f23","f24","f25","f26","f27","f28","f29","f30","f31",
     "", "pc","ps","cr","lr","ctr","xer"]
     (gdb)
     -data-list-register-names 1 2 3
     ^done,register-names=["r1","r2","r3"]
     (gdb)
</pre>
   <h4 class="subheading">The <code>-data-list-register-values</code> Command</h4>

<p><a name="index-g_t_002ddata_002dlist_002dregister_002dvalues-3052"></a>

<h5 class="subsubheading">Synopsis</h5>

<pre class="smallexample">      -data-list-register-values
         [ <code>--skip-unavailable</code> ] <var>fmt</var> [ ( <var>regno</var> )*]
</pre>
   <p>Display the registers' contents.  The format according to which the
registers' contents are to be returned is given by <var>fmt</var>, followed
by an optional list of numbers specifying the registers to display.  A
missing list of numbers indicates that the contents of all the
registers must be returned.  The <code>--skip-unavailable</code> option
indicates that only the available registers are to be returned.

   <p>Allowed formats for <var>fmt</var> are:

     <dl>
<dt><code>x</code><dd>Hexadecimal
<br><dt><code>o</code><dd>Octal
<br><dt><code>t</code><dd>Binary
<br><dt><code>d</code><dd>Decimal
<br><dt><code>r</code><dd>Raw
<br><dt><code>N</code><dd>Natural
</dl>

<h5 class="subsubheading"><span class="sc">gdb</span> Command</h5>

<p>The corresponding <span class="sc">gdb</span> commands are &lsquo;<samp><span class="samp">info reg</span></samp>&rsquo;, &lsquo;<samp><span class="samp">info
all-reg</span></samp>&rsquo;, and (in <code>gdbtk</code>) &lsquo;<samp><span class="samp">gdb_fetch_registers</span></samp>&rsquo;.

<h5 class="subsubheading">Example</h5>

<p>For a PPC MBX board (note: line breaks are for readability only, they
don't appear in the actual output):

<pre class="smallexample">     (gdb)
     -data-list-register-values r 64 65
     ^done,register-values=[{number="64",value="0xfe00a300"},
     {number="65",value="0x00029002"}]
     (gdb)
     -data-list-register-values x
     ^done,register-values=[{number="0",value="0xfe0043c8"},
     {number="1",value="0x3fff88"},{number="2",value="0xfffffffe"},
     {number="3",value="0x0"},{number="4",value="0xa"},
     {number="5",value="0x3fff68"},{number="6",value="0x3fff58"},
     {number="7",value="0xfe011e98"},{number="8",value="0x2"},
     {number="9",value="0xfa202820"},{number="10",value="0xfa202808"},
     {number="11",value="0x1"},{number="12",value="0x0"},
     {number="13",value="0x4544"},{number="14",value="0xffdfffff"},
     {number="15",value="0xffffffff"},{number="16",value="0xfffffeff"},
     {number="17",value="0xefffffed"},{number="18",value="0xfffffffe"},
     {number="19",value="0xffffffff"},{number="20",value="0xffffffff"},
     {number="21",value="0xffffffff"},{number="22",value="0xfffffff7"},
     {number="23",value="0xffffffff"},{number="24",value="0xffffffff"},
     {number="25",value="0xffffffff"},{number="26",value="0xfffffffb"},
     {number="27",value="0xffffffff"},{number="28",value="0xf7bfffff"},
     {number="29",value="0x0"},{number="30",value="0xfe010000"},
     {number="31",value="0x0"},{number="32",value="0x0"},
     {number="33",value="0x0"},{number="34",value="0x0"},
     {number="35",value="0x0"},{number="36",value="0x0"},
     {number="37",value="0x0"},{number="38",value="0x0"},
     {number="39",value="0x0"},{number="40",value="0x0"},
     {number="41",value="0x0"},{number="42",value="0x0"},
     {number="43",value="0x0"},{number="44",value="0x0"},
     {number="45",value="0x0"},{number="46",value="0x0"},
     {number="47",value="0x0"},{number="48",value="0x0"},
     {number="49",value="0x0"},{number="50",value="0x0"},
     {number="51",value="0x0"},{number="52",value="0x0"},
     {number="53",value="0x0"},{number="54",value="0x0"},
     {number="55",value="0x0"},{number="56",value="0x0"},
     {number="57",value="0x0"},{number="58",value="0x0"},
     {number="59",value="0x0"},{number="60",value="0x0"},
     {number="61",value="0x0"},{number="62",value="0x0"},
     {number="63",value="0x0"},{number="64",value="0xfe00a300"},
     {number="65",value="0x29002"},{number="66",value="0x202f04b5"},
     {number="67",value="0xfe0043b0"},{number="68",value="0xfe00b3e4"},
     {number="69",value="0x20002b03"}]
     (gdb)
</pre>
   <h4 class="subheading">The <code>-data-read-memory</code> Command</h4>

<p><a name="index-g_t_002ddata_002dread_002dmemory-3053"></a>
This command is deprecated, use <code>-data-read-memory-bytes</code> instead.

<h5 class="subsubheading">Synopsis</h5>

<pre class="smallexample">      -data-read-memory [ -o <var>byte-offset</var> ]
        <var>address</var> <var>word-format</var> <var>word-size</var>
        <var>nr-rows</var> <var>nr-cols</var> [ <var>aschar</var> ]
</pre>
<p class="noindent">where:

     <dl>
<dt>&lsquo;<samp><var>address</var></samp>&rsquo;<dd>An expression specifying the address of the first memory word to be
read.  Complex expressions containing embedded white space should be
quoted using the C convention.

     <br><dt>&lsquo;<samp><var>word-format</var></samp>&rsquo;<dd>The format to be used to print the memory words.  The notation is the
same as for <span class="sc">gdb</span>'s <code>print</code> command (see <a href="Output-Formats.html#Output-Formats">Output Formats</a>).

     <br><dt>&lsquo;<samp><var>word-size</var></samp>&rsquo;<dd>The size of each memory word in bytes.

     <br><dt>&lsquo;<samp><var>nr-rows</var></samp>&rsquo;<dd>The number of rows in the output table.

     <br><dt>&lsquo;<samp><var>nr-cols</var></samp>&rsquo;<dd>The number of columns in the output table.

     <br><dt>&lsquo;<samp><var>aschar</var></samp>&rsquo;<dd>If present, indicates that each row should include an <span class="sc">ascii</span> dump.  The
value of <var>aschar</var> is used as a padding character when a byte is not a
member of the printable <span class="sc">ascii</span> character set (printable <span class="sc">ascii</span>
characters are those whose code is between 32 and 126, inclusively).

     <br><dt>&lsquo;<samp><var>byte-offset</var></samp>&rsquo;<dd>An offset to add to the <var>address</var> before fetching memory. 
</dl>

   <p>This command displays memory contents as a table of <var>nr-rows</var> by
<var>nr-cols</var> words, each word being <var>word-size</var> bytes.  In total,
<var>nr-rows</var><code> * </code><var>nr-cols</var><code> * </code><var>word-size</var> bytes are read
(returned as &lsquo;<samp><span class="samp">total-bytes</span></samp>&rsquo;).  Should less than the requested number
of bytes be returned by the target, the missing words are identified
using &lsquo;<samp><span class="samp">N/A</span></samp>&rsquo;.  The number of bytes read from the target is returned
in &lsquo;<samp><span class="samp">nr-bytes</span></samp>&rsquo; and the starting address used to read memory in
&lsquo;<samp><span class="samp">addr</span></samp>&rsquo;.

   <p>The address of the next/previous row or page is available in
&lsquo;<samp><span class="samp">next-row</span></samp>&rsquo; and &lsquo;<samp><span class="samp">prev-row</span></samp>&rsquo;, &lsquo;<samp><span class="samp">next-page</span></samp>&rsquo; and
&lsquo;<samp><span class="samp">prev-page</span></samp>&rsquo;.

<h5 class="subsubheading"><span class="sc">gdb</span> Command</h5>

<p>The corresponding <span class="sc">gdb</span> command is &lsquo;<samp><span class="samp">x</span></samp>&rsquo;.  <code>gdbtk</code> has
&lsquo;<samp><span class="samp">gdb_get_mem</span></samp>&rsquo; memory read command.

<h5 class="subsubheading">Example</h5>

<p>Read six bytes of memory starting at <code>bytes+6</code> but then offset by
<code>-6</code> bytes.  Format as three rows of two columns.  One byte per
word.  Display each word in hex.

<pre class="smallexample">     (gdb)
     9-data-read-memory -o -6 -- bytes+6 x 1 3 2
     9^done,addr="0x00001390",nr-bytes="6",total-bytes="6",
     next-row="0x00001396",prev-row="0x0000138e",next-page="0x00001396",
     prev-page="0x0000138a",memory=[
     {addr="0x00001390",data=["0x00","0x01"]},
     {addr="0x00001392",data=["0x02","0x03"]},
     {addr="0x00001394",data=["0x04","0x05"]}]
     (gdb)
</pre>
   <p>Read two bytes of memory starting at address <code>shorts + 64</code> and
display as a single word formatted in decimal.

<pre class="smallexample">     (gdb)
     5-data-read-memory shorts+64 d 2 1 1
     5^done,addr="0x00001510",nr-bytes="2",total-bytes="2",
     next-row="0x00001512",prev-row="0x0000150e",
     next-page="0x00001512",prev-page="0x0000150e",memory=[
     {addr="0x00001510",data=["128"]}]
     (gdb)
</pre>
   <p>Read thirty two bytes of memory starting at <code>bytes+16</code> and format
as eight rows of four columns.  Include a string encoding with &lsquo;<samp><span class="samp">x</span></samp>&rsquo;
used as the non-printable character.

<pre class="smallexample">     (gdb)
     4-data-read-memory bytes+16 x 1 8 4 x
     4^done,addr="0x000013a0",nr-bytes="32",total-bytes="32",
     next-row="0x000013c0",prev-row="0x0000139c",
     next-page="0x000013c0",prev-page="0x00001380",memory=[
     {addr="0x000013a0",data=["0x10","0x11","0x12","0x13"],ascii="xxxx"},
     {addr="0x000013a4",data=["0x14","0x15","0x16","0x17"],ascii="xxxx"},
     {addr="0x000013a8",data=["0x18","0x19","0x1a","0x1b"],ascii="xxxx"},
     {addr="0x000013ac",data=["0x1c","0x1d","0x1e","0x1f"],ascii="xxxx"},
     {addr="0x000013b0",data=["0x20","0x21","0x22","0x23"],ascii=" !\"#"},
     {addr="0x000013b4",data=["0x24","0x25","0x26","0x27"],ascii="$%&amp;'"},
     {addr="0x000013b8",data=["0x28","0x29","0x2a","0x2b"],ascii="()*+"},
     {addr="0x000013bc",data=["0x2c","0x2d","0x2e","0x2f"],ascii=",-./"}]
     (gdb)
</pre>
   <h4 class="subheading">The <code>-data-read-memory-bytes</code> Command</h4>

<p><a name="index-g_t_002ddata_002dread_002dmemory_002dbytes-3054"></a>

<h5 class="subsubheading">Synopsis</h5>

<pre class="smallexample">      -data-read-memory-bytes [ -o <var>offset</var> ]
        <var>address</var> <var>count</var>
</pre>
<p class="noindent">where:

     <dl>
<dt>&lsquo;<samp><var>address</var></samp>&rsquo;<dd>An expression specifying the address of the first addressable memory unit
to be read.  Complex expressions containing embedded white space should be
quoted using the C convention.

     <br><dt>&lsquo;<samp><var>count</var></samp>&rsquo;<dd>The number of addressable memory units to read.  This should be an integer
literal.

     <br><dt>&lsquo;<samp><var>offset</var></samp>&rsquo;<dd>The offset relative to <var>address</var> at which to start reading.  This
should be an integer literal.  This option is provided so that a frontend
is not required to first evaluate address and then perform address
arithmetics itself.

   </dl>

   <p>This command attempts to read all accessible memory regions in the
specified range.  First, all regions marked as unreadable in the memory
map (if one is defined) will be skipped.  See <a href="Memory-Region-Attributes.html#Memory-Region-Attributes">Memory Region Attributes</a>.  Second, <span class="sc">gdb</span> will attempt to read the remaining
regions.  For each one, if reading full region results in an errors,
<span class="sc">gdb</span> will try to read a subset of the region.

   <p>In general, every single memory unit in the region may be readable or not,
and the only way to read every readable unit is to try a read at
every address, which is not practical.   Therefore, <span class="sc">gdb</span> will
attempt to read all accessible memory units at either beginning or the end
of the region, using a binary division scheme.  This heuristic works
well for reading accross a memory map boundary.  Note that if a region
has a readable range that is neither at the beginning or the end,
<span class="sc">gdb</span> will not read it.

   <p>The result record (see <a href="GDB_002fMI-Result-Records.html#GDB_002fMI-Result-Records">GDB/MI Result Records</a>) that is output of
the command includes a field named &lsquo;<samp><span class="samp">memory</span></samp>&rsquo; whose content is a
list of tuples.  Each tuple represent a successfully read memory block
and has the following fields:

     <dl>
<dt><code>begin</code><dd>The start address of the memory block, as hexadecimal literal.

     <br><dt><code>end</code><dd>The end address of the memory block, as hexadecimal literal.

     <br><dt><code>offset</code><dd>The offset of the memory block, as hexadecimal literal, relative to
the start address passed to <code>-data-read-memory-bytes</code>.

     <br><dt><code>contents</code><dd>The contents of the memory block, in hex.

   </dl>

<h5 class="subsubheading"><span class="sc">gdb</span> Command</h5>

<p>The corresponding <span class="sc">gdb</span> command is &lsquo;<samp><span class="samp">x</span></samp>&rsquo;.

<h5 class="subsubheading">Example</h5>

<pre class="smallexample">     (gdb)
     -data-read-memory-bytes &amp;a 10
     ^done,memory=[{begin="0xbffff154",offset="0x00000000",
                   end="0xbffff15e",
                   contents="01000000020000000300"}]
     (gdb)
</pre>
<h4 class="subheading">The <code>-data-write-memory-bytes</code> Command</h4>

<p><a name="index-g_t_002ddata_002dwrite_002dmemory_002dbytes-3055"></a>

<h5 class="subsubheading">Synopsis</h5>

<pre class="smallexample">      -data-write-memory-bytes <var>address</var> <var>contents</var>
      -data-write-memory-bytes <var>address</var> <var>contents</var> <span class="roman">[</span><var>count</var><span class="roman">]</span>
</pre>
<p class="noindent">where:

     <dl>
<dt>&lsquo;<samp><var>address</var></samp>&rsquo;<dd>An expression specifying the address of the first addressable memory unit
to be written.  Complex expressions containing embedded white space should
be quoted using the C convention.

     <br><dt>&lsquo;<samp><var>contents</var></samp>&rsquo;<dd>The hex-encoded data to write.  It is an error if <var>contents</var> does
not represent an integral number of addressable memory units.

     <br><dt>&lsquo;<samp><var>count</var></samp>&rsquo;<dd>Optional argument indicating the number of addressable memory units to be
written.  If <var>count</var> is greater than <var>contents</var>' length,
<span class="sc">gdb</span> will repeatedly write <var>contents</var> until it fills
<var>count</var> memory units.

   </dl>

<h5 class="subsubheading"><span class="sc">gdb</span> Command</h5>

<p>There's no corresponding <span class="sc">gdb</span> command.

<h5 class="subsubheading">Example</h5>

<pre class="smallexample">     (gdb)
     -data-write-memory-bytes &amp;a "aabbccdd"
     ^done
     (gdb)
</pre>
<pre class="smallexample">     (gdb)
     -data-write-memory-bytes &amp;a "aabbccdd" 16e
     ^done
     (gdb)
</pre>
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