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| <h2 class="chapter">3 Constants</h2> |
| |
| <p>The ‘<samp><span class="samp">c</span></samp>’ symbol descriptor indicates that this stab represents a |
| constant. This symbol descriptor is an exception to the general rule |
| that symbol descriptors are followed by type information. Instead, it |
| is followed by ‘<samp><span class="samp">=</span></samp>’ and one of the following: |
| |
| <dl> |
| <dt><code>b </code><var>value</var><dd>Boolean constant. <var>value</var> is a numeric value; I assume it is 0 for |
| false or 1 for true. |
| |
| <br><dt><code>c </code><var>value</var><dd>Character constant. <var>value</var> is the numeric value of the constant. |
| |
| <br><dt><code>e </code><var>type-information</var><code> , </code><var>value</var><dd>Constant whose value can be represented as integral. |
| <var>type-information</var> is the type of the constant, as it would appear |
| after a symbol descriptor (see <a href="String-Field.html#String-Field">String Field</a>). <var>value</var> is the |
| numeric value of the constant. GDB 4.9 does not actually get the right |
| value if <var>value</var> does not fit in a host <code>int</code>, but it does not |
| do anything violent, and future debuggers could be extended to accept |
| integers of any size (whether unsigned or not). This constant type is |
| usually documented as being only for enumeration constants, but GDB has |
| never imposed that restriction; I don't know about other debuggers. |
| |
| <br><dt><code>i </code><var>value</var><dd>Integer constant. <var>value</var> is the numeric value. The type is some |
| sort of generic integer type (for GDB, a host <code>int</code>); to specify |
| the type explicitly, use ‘<samp><span class="samp">e</span></samp>’ instead. |
| |
| <br><dt><code>r </code><var>value</var><dd>Real constant. <var>value</var> is the real value, which can be ‘<samp><span class="samp">INF</span></samp>’ |
| (optionally preceded by a sign) for infinity, ‘<samp><span class="samp">QNAN</span></samp>’ for a quiet |
| NaN (not-a-number), or ‘<samp><span class="samp">SNAN</span></samp>’ for a signalling NaN. If it is a |
| normal number the format is that accepted by the C library function |
| <code>atof</code>. |
| |
| <br><dt><code>s </code><var>string</var><dd>String constant. <var>string</var> is a string enclosed in either ‘<samp><span class="samp">'</span></samp>’ |
| (in which case ‘<samp><span class="samp">'</span></samp>’ characters within the string are represented as |
| ‘<samp><span class="samp">\'</span></samp>’ or ‘<samp><span class="samp">"</span></samp>’ (in which case ‘<samp><span class="samp">"</span></samp>’ characters within the |
| string are represented as ‘<samp><span class="samp">\"</span></samp>’). |
| |
| <br><dt><code>S </code><var>type-information</var><code> , </code><var>elements</var><code> , </code><var>bits</var><code> , </code><var>pattern</var><dd>Set constant. <var>type-information</var> is the type of the constant, as it |
| would appear after a symbol descriptor (see <a href="String-Field.html#String-Field">String Field</a>). |
| <var>elements</var> is the number of elements in the set (does this means |
| how many bits of <var>pattern</var> are actually used, which would be |
| redundant with the type, or perhaps the number of bits set in |
| <var>pattern</var>? I don't get it), <var>bits</var> is the number of bits in the |
| constant (meaning it specifies the length of <var>pattern</var>, I think), |
| and <var>pattern</var> is a hexadecimal representation of the set. AIX |
| documentation refers to a limit of 32 bytes, but I see no reason why |
| this limit should exist. This form could probably be used for arbitrary |
| constants, not just sets; the only catch is that <var>pattern</var> should be |
| understood to be target, not host, byte order and format. |
| </dl> |
| |
| <p>The boolean, character, string, and set constants are not supported by |
| GDB 4.9, but it ignores them. GDB 4.8 and earlier gave an error |
| message and refused to read symbols from the file containing the |
| constants. |
| |
| <p>The above information is followed by ‘<samp><span class="samp">;</span></samp>’. |
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