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<title>Value Annotations - GDB's Obsolete Annotations</title>
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<a name="Value-Annotations"></a>
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Next: <a rel="next" accesskey="n" href="Frame-Annotations.html#Frame-Annotations">Frame Annotations</a>,
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Previous: <a rel="previous" accesskey="p" href="Server-Prefix.html#Server-Prefix">Server Prefix</a>,
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Up: <a rel="up" accesskey="u" href="index.html#Top">Top</a>
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<h2 class="chapter">5 Values</h2>
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<p><em>Value Annotations have been removed. </em><span class="sc">gdb/mi</span><em> instead provides
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Variable Objects.</em>
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<p><a name="index-annotations-for-values-3"></a>When a value is printed in various contexts, <span class="sc">gdb</span> uses
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annotations to delimit the value from the surrounding text.
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<p><a name="index-value_002dhistory_002dbegin-4"></a><a name="index-value_002dhistory_002dvalue-5"></a><a name="index-value_002dhistory_002dend-6"></a>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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<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>
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<p class="noindent">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><span class="samp">$5 = </span></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><span class="samp">*</span></samp>’ for
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a value which can be dereferenced and ‘<samp><span class="samp">-</span></samp>’ for a value which cannot.
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<p><a name="index-value_002dbegin-7"></a><a name="index-value_002dend-8"></a>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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<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>
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<p><a name="index-arg_002dbegin-9"></a><a name="index-arg_002dname_002dend-10"></a><a name="index-arg_002dvalue-11"></a><a name="index-arg_002dend-12"></a>When <span class="sc">gdb</span> 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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<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>
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<p class="noindent">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><span class="samp">=</span></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><a name="index-field_002dbegin-13"></a><a name="index-field_002dname_002dend-14"></a><a name="index-field_002dvalue-15"></a><a name="index-field_002dend-16"></a>When printing a structure, <span class="sc">gdb</span> annotates it as follows:
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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>
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<p class="noindent">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><span class="samp">=</span></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>When printing an array, <span class="sc">gdb</span> annotates it as follows:
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<pre class="smallexample"> ^Z^Zarray-section-begin <var>array-index</var> <var>value-flags</var>
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</pre>
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<p class="noindent">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><a name="index-elt-17"></a>
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<pre class="smallexample"> ‘<samp><span class="samp">,</span></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>
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<p>or a repeated element
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<p><a name="index-elt_002drep-18"></a><a name="index-elt_002drep_002dend-19"></a>
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<pre class="smallexample"> ‘<samp><span class="samp">,</span></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>
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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><a name="index-array_002dsection_002dend-20"></a>Once all the array elements have been output, the array annotation is
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ended with
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<pre class="smallexample"> ^Z^Zarray-section-end
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</pre>
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