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| <h5 class="subsubsection">A.2.2.1 Syntax for Variable Arguments</h5> |
| |
| <p><a name="index-function-prototypes-_0028variadic_0029-3712"></a><a name="index-prototypes-for-variadic-functions-3713"></a><a name="index-variadic-function-prototypes-3714"></a> |
| A function that accepts a variable number of arguments must be declared |
| with a prototype that says so. You write the fixed arguments as usual, |
| and then tack on ‘<samp><span class="samp">...</span></samp>’ to indicate the possibility of |
| additional arguments. The syntax of ISO C<!-- /@w --> requires at least one fixed |
| argument before the ‘<samp><span class="samp">...</span></samp>’. For example, |
| |
| <pre class="smallexample"> int |
| func (const char *a, int b, ...) |
| { |
| ... |
| } |
| </pre> |
| <p class="noindent">defines a function <code>func</code> which returns an <code>int</code> and takes two |
| required arguments, a <code>const char *</code> and an <code>int</code>. These are |
| followed by any number of anonymous arguments. |
| |
| <p><strong>Portability note:</strong> For some C compilers, the last required |
| argument must not be declared <code>register</code> in the function |
| definition. Furthermore, this argument's type must be |
| <dfn>self-promoting</dfn>: that is, the default promotions must not change |
| its type. This rules out array and function types, as well as |
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