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| <h2 class="chapter">5 Values</h2> |
| |
| <p><em>Value Annotations have been removed. </em><span class="sc">gdb/mi</span><em> instead provides |
| Variable Objects.</em> |
| |
| <p><a name="index-annotations-for-values-3"></a>When a value is printed in various contexts, <span class="sc">gdb</span> uses |
| annotations to delimit the value from the surrounding text. |
| |
| <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, |
| the annotation looks like |
| |
| <pre class="smallexample"> ^Z^Zvalue-history-begin <var>history-number</var> <var>value-flags</var> |
| <var>history-string</var> |
| ^Z^Zvalue-history-value |
| <var>the-value</var> |
| ^Z^Zvalue-history-end |
| </pre> |
| <p class="noindent">where <var>history-number</var> is the number it is getting in the value |
| history, <var>history-string</var> is a string, such as ‘<samp><span class="samp">$5 = </span></samp>’, which |
| introduces the value to the user, <var>the-value</var> is the output |
| corresponding to the value itself, and <var>value-flags</var> is ‘<samp><span class="samp">*</span></samp>’ for |
| a value which can be dereferenced and ‘<samp><span class="samp">-</span></samp>’ for a value which cannot. |
| |
| <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 |
| or it is printed with the <code>output</code> command), the annotation is similar: |
| |
| <pre class="smallexample"> ^Z^Zvalue-begin <var>value-flags</var> |
| <var>the-value</var> |
| ^Z^Zvalue-end |
| </pre> |
| <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 |
| from the <code>backtrace</code> command), it annotates it as follows: |
| |
| <pre class="smallexample"> ^Z^Zarg-begin |
| <var>argument-name</var> |
| ^Z^Zarg-name-end |
| <var>separator-string</var> |
| ^Z^Zarg-value <var>value-flags</var> |
| <var>the-value</var> |
| ^Z^Zarg-end |
| </pre> |
| <p class="noindent">where <var>argument-name</var> is the name of the argument, |
| <var>separator-string</var> is text which separates the name from the value |
| for the user's benefit (such as ‘<samp><span class="samp">=</span></samp>’), and <var>value-flags</var> and |
| <var>the-value</var> have the same meanings as in a |
| <code>value-history-begin</code> annotation. |
| |
| <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: |
| |
| <pre class="smallexample"> ^Z^Zfield-begin <var>value-flags</var> |
| <var>field-name</var> |
| ^Z^Zfield-name-end |
| <var>separator-string</var> |
| ^Z^Zfield-value |
| <var>the-value</var> |
| ^Z^Zfield-end |
| </pre> |
| <p class="noindent">where <var>field-name</var> is the name of the field, <var>separator-string</var> |
| is text which separates the name from the value for the user's benefit |
| (such as ‘<samp><span class="samp">=</span></samp>’), and <var>value-flags</var> and <var>the-value</var> have the |
| same meanings as in a <code>value-history-begin</code> annotation. |
| |
| <p>When printing an array, <span class="sc">gdb</span> annotates it as follows: |
| |
| <pre class="smallexample"> ^Z^Zarray-section-begin <var>array-index</var> <var>value-flags</var> |
| </pre> |
| <p class="noindent">where <var>array-index</var> is the index of the first element being |
| annotated and <var>value-flags</var> has the same meaning as in a |
| <code>value-history-begin</code> annotation. This is followed by any number |
| of elements, where is element can be either a single element: |
| |
| <p><a name="index-elt-17"></a> |
| <pre class="smallexample"> ‘<samp><span class="samp">,</span></samp>’ <var>whitespace</var> ; <span class="roman">omitted for the first element</span> |
| <var>the-value</var> |
| ^Z^Zelt |
| </pre> |
| <p>or a repeated element |
| |
| <p><a name="index-elt_002drep-18"></a><a name="index-elt_002drep_002dend-19"></a> |
| <pre class="smallexample"> ‘<samp><span class="samp">,</span></samp>’ <var>whitespace</var> ; <span class="roman">omitted for the first element</span> |
| <var>the-value</var> |
| ^Z^Zelt-rep <var>number-of-repetitions</var> |
| <var>repetition-string</var> |
| ^Z^Zelt-rep-end |
| </pre> |
| <p>In both cases, <var>the-value</var> is the output for the value of the |
| element and <var>whitespace</var> can contain spaces, tabs, and newlines. In |
| the repeated case, <var>number-of-repetitions</var> is the number of |
| consecutive array elements which contain that value, and |
| <var>repetition-string</var> is a string which is designed to convey to the |
| user that repetition is being depicted. |
| |
| <p><a name="index-array_002dsection_002dend-20"></a>Once all the array elements have been output, the array annotation is |
| ended with |
| |
| <pre class="smallexample"> ^Z^Zarray-section-end |
| </pre> |
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| |
