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| <h3 class="section">5.11 Function Types</h3> |
| |
| <p>Various types can be defined for function variables. These types are |
| not used in defining functions (see <a href="Procedures.html#Procedures">Procedures</a>); they are used for |
| things like pointers to functions. |
| |
| <p>The simple, traditional, type is type descriptor ‘<samp><span class="samp">f</span></samp>’ is followed by |
| type information for the return type of the function, followed by a |
| semicolon. |
| |
| <p>This does not deal with functions for which the number and types of the |
| parameters are part of the type, as in Modula-2 or ANSI C. AIX provides |
| extensions to specify these, using the ‘<samp><span class="samp">f</span></samp>’, ‘<samp><span class="samp">F</span></samp>’, ‘<samp><span class="samp">p</span></samp>’, and |
| ‘<samp><span class="samp">R</span></samp>’ type descriptors. |
| |
| <p>First comes the type descriptor. If it is ‘<samp><span class="samp">f</span></samp>’ or ‘<samp><span class="samp">F</span></samp>’, this |
| type involves a function rather than a procedure, and the type |
| information for the return type of the function follows, followed by a |
| comma. Then comes the number of parameters to the function and a |
| semicolon. Then, for each parameter, there is the name of the parameter |
| followed by a colon (this is only present for type descriptors ‘<samp><span class="samp">R</span></samp>’ |
| and ‘<samp><span class="samp">F</span></samp>’ which represent Pascal function or procedure parameters), |
| type information for the parameter, a comma, 0 if passed by reference or |
| 1 if passed by value, and a semicolon. The type definition ends with a |
| semicolon. |
| |
| <p>For example, this variable definition: |
| |
| <pre class="example"> int (*g_pf)(); |
| </pre> |
| <p class="noindent">generates the following code: |
| |
| <pre class="example"> .stabs "g_pf:G24=*25=f1",32,0,0,0 |
| .common _g_pf,4,"bss" |
| </pre> |
| <p>The variable defines a new type, 24, which is a pointer to another new |
| type, 25, which is a function returning <code>int</code>. |
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