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<title>GDB’s Obsolete Annotations: Value Annotations</title>
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<a name="Value-Annotations"></a>
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<div class="header">
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<p>
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Next: <a href="Frame-Annotations.html#Frame-Annotations" accesskey="n" rel="next">Frame Annotations</a>, Previous: <a href="Server-Prefix.html#Server-Prefix" accesskey="p" rel="previous">Server Prefix</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>]</p>
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<hr>
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<a name="Values"></a>
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<h2 class="chapter">5 Values</h2>
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<p><em>Value Annotations have been removed. <small>GDB/MI</small> instead provides
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Variable Objects.</em>
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</p>
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<a name="index-annotations-for-values"></a>
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<p>When a value is printed in various contexts, <small>GDB</small> uses
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annotations to delimit the value from the surrounding text.
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</p>
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<a name="index-value_002dhistory_002dbegin"></a>
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<a name="index-value_002dhistory_002dvalue"></a>
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<a name="index-value_002dhistory_002dend"></a>
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<p>If a value is printed using <code>print</code> and added to the value history,
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the annotation looks like
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</p>
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<div class="smallexample">
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<pre class="smallexample">^Z^Zvalue-history-begin <var>history-number</var> <var>value-flags</var>
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<var>history-string</var>
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^Z^Zvalue-history-value
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<var>the-value</var>
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^Z^Zvalue-history-end
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</pre></div>
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<p>where <var>history-number</var> is the number it is getting in the value
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history, <var>history-string</var> is a string, such as ‘<samp>$5 = </samp>’, which
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introduces the value to the user, <var>the-value</var> is the output
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corresponding to the value itself, and <var>value-flags</var> is ‘<samp>*</samp>’ for
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a value which can be dereferenced and ‘<samp>-</samp>’ for a value which cannot.
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</p>
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<a name="index-value_002dbegin"></a>
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<a name="index-value_002dend"></a>
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<p>If the value is not added to the value history (it is an invalid float
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or it is printed with the <code>output</code> command), the annotation is similar:
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</p>
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<div class="smallexample">
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<pre class="smallexample">^Z^Zvalue-begin <var>value-flags</var>
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<var>the-value</var>
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^Z^Zvalue-end
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</pre></div>
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<a name="index-arg_002dbegin"></a>
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<a name="index-arg_002dname_002dend"></a>
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<a name="index-arg_002dvalue"></a>
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<a name="index-arg_002dend"></a>
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<p>When <small>GDB</small> prints an argument to a function (for example, in the output
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from the <code>backtrace</code> command), it annotates it as follows:
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</p>
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<div class="smallexample">
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<pre class="smallexample">^Z^Zarg-begin
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<var>argument-name</var>
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^Z^Zarg-name-end
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<var>separator-string</var>
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^Z^Zarg-value <var>value-flags</var>
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<var>the-value</var>
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^Z^Zarg-end
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</pre></div>
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<p>where <var>argument-name</var> is the name of the argument,
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<var>separator-string</var> is text which separates the name from the value
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for the user’s benefit (such as ‘<samp>=</samp>’), and <var>value-flags</var> and
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<var>the-value</var> have the same meanings as in a
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<code>value-history-begin</code> annotation.
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</p>
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<a name="index-field_002dbegin"></a>
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<a name="index-field_002dname_002dend"></a>
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<a name="index-field_002dvalue"></a>
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<a name="index-field_002dend"></a>
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<p>When printing a structure, <small>GDB</small> annotates it as follows:
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</p>
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<div class="smallexample">
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<pre class="smallexample">^Z^Zfield-begin <var>value-flags</var>
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<var>field-name</var>
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^Z^Zfield-name-end
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<var>separator-string</var>
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^Z^Zfield-value
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<var>the-value</var>
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^Z^Zfield-end
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</pre></div>
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<p>where <var>field-name</var> is the name of the field, <var>separator-string</var>
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is text which separates the name from the value for the user’s benefit
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(such as ‘<samp>=</samp>’), and <var>value-flags</var> and <var>the-value</var> have the
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same meanings as in a <code>value-history-begin</code> annotation.
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</p>
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<p>When printing an array, <small>GDB</small> annotates it as follows:
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</p>
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<div class="smallexample">
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<pre class="smallexample">^Z^Zarray-section-begin <var>array-index</var> <var>value-flags</var>
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</pre></div>
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<p>where <var>array-index</var> is the index of the first element being
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annotated and <var>value-flags</var> has the same meaning as in a
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<code>value-history-begin</code> annotation. This is followed by any number
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of elements, where is element can be either a single element:
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</p>
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<a name="index-elt"></a>
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<div class="smallexample">
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<pre class="smallexample">‘<samp>,</samp>’ <var>whitespace</var> ; <span class="roman">omitted for the first element</span>
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<var>the-value</var>
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^Z^Zelt
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</pre></div>
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<p>or a repeated element
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</p>
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<a name="index-elt_002drep"></a>
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<a name="index-elt_002drep_002dend"></a>
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<div class="smallexample">
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<pre class="smallexample">‘<samp>,</samp>’ <var>whitespace</var> ; <span class="roman">omitted for the first element</span>
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<var>the-value</var>
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^Z^Zelt-rep <var>number-of-repetitions</var>
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<var>repetition-string</var>
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^Z^Zelt-rep-end
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</pre></div>
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<p>In both cases, <var>the-value</var> is the output for the value of the
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element and <var>whitespace</var> can contain spaces, tabs, and newlines. In
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the repeated case, <var>number-of-repetitions</var> is the number of
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consecutive array elements which contain that value, and
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<var>repetition-string</var> is a string which is designed to convey to the
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user that repetition is being depicted.
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</p>
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<a name="index-array_002dsection_002dend"></a>
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<p>Once all the array elements have been output, the array annotation is
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ended with
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</p>
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<div class="smallexample">
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<pre class="smallexample">^Z^Zarray-section-end
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</pre></div>
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<p>
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Next: <a href="Frame-Annotations.html#Frame-Annotations" accesskey="n" rel="next">Frame Annotations</a>, Previous: <a href="Server-Prefix.html#Server-Prefix" accesskey="p" rel="previous">Server Prefix</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>]</p>
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