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| <h3 class="section">5.7 Enumerations</h3> |
| |
| <p>Enumerations are defined with the ‘<samp><span class="samp">e</span></samp>’ type descriptor. |
| |
| <!-- FIXME: Where does this information properly go? Perhaps it is --> |
| <!-- redundant with something we already explain. --> |
| <p>The source line below declares an enumeration type at file scope. |
| The type definition is located after the <code>N_RBRAC</code> that marks the end of |
| the previous procedure's block scope, and before the <code>N_FUN</code> that marks |
| the beginning of the next procedure's block scope. Therefore it does not |
| describe a block local symbol, but a file local one. |
| |
| <p>The source line: |
| |
| <pre class="example"> enum e_places {first,second=3,last}; |
| </pre> |
| <p class="noindent">generates the following stab: |
| |
| <pre class="example"> .stabs "e_places:T22=efirst:0,second:3,last:4,;",128,0,0,0 |
| </pre> |
| <p>The symbol descriptor (‘<samp><span class="samp">T</span></samp>’) says that the stab describes a |
| structure, enumeration, or union tag. The type descriptor ‘<samp><span class="samp">e</span></samp>’, |
| following the ‘<samp><span class="samp">22=</span></samp>’ of the type definition narrows it down to an |
| enumeration type. Following the ‘<samp><span class="samp">e</span></samp>’ is a list of the elements of |
| the enumeration. The format is ‘<samp><var>name</var><span class="samp">:</span><var>value</var><span class="samp">,</span></samp>’. The |
| list of elements ends with ‘<samp><span class="samp">;</span></samp>’. The fact that <var>value</var> is |
| specified as an integer can cause problems if the value is large. GCC |
| 2.5.2 tries to output it in octal in that case with a leading zero, |
| which is probably a good thing, although GDB 4.11 supports octal only in |
| cases where decimal is perfectly good. Negative decimal values are |
| supported by both GDB and dbx. |
| |
| <p>There is no standard way to specify the size of an enumeration type; it |
| is determined by the architecture (normally all enumerations types are |
| 32 bits). Type attributes can be used to specify an enumeration type of |
| another size for debuggers which support them; see <a href="String-Field.html#String-Field">String Field</a>. |
| |
| <p>Enumeration types are unusual in that they define symbols for the |
| enumeration values (<code>first</code>, <code>second</code>, and <code>third</code> in the |
| above example), and even though these symbols are visible in the file as |
| a whole (rather than being in a more local namespace like structure |
| member names), they are defined in the type definition for the |
| enumeration type rather than each having their own symbol. In order to |
| be fast, GDB will only get symbols from such types (in its initial scan |
| of the stabs) if the type is the first thing defined after a ‘<samp><span class="samp">T</span></samp>’ or |
| ‘<samp><span class="samp">t</span></samp>’ symbol descriptor (the above example fulfills this |
| requirement). If the type does not have a name, the compiler should |
| emit it in a nameless stab (see <a href="String-Field.html#String-Field">String Field</a>); GCC does this. |
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