As BrowserUK suggests, C doesn't have Optional arguments. However C++ does (with some constraints). In essence the C++ compiler takes care of it for you by providing the default value at call time if you haven't provided a value yourself. C++ also provides function overloading where different functions with the same name (but different prototypes) may be used. If you are really dealing with sparsely documented C++ then you are in a world of pain.

Actually, if it is C++ then the situation is even worse because C++ mangles identifiers. The identifier the linker sees is not the identifier that was compiled, and there are no rules for how that mangling is done.

Arguments that are notionally optional in C generally accept a 0 (NULL) if they are not being provided. Most often such arguments are pointers so you are simply passing a null pointer to the function.

Perl is environmentally friendly - it saves trees

In reply to Re: functions with optional arguments in Windows DLLs by GrandFather
in thread functions with optional arguments in Windows DLLs by spurperl

Title:
Use:  <p> text here (a paragraph) </p>
and:  <code> code here </code>
to format your post, it's "PerlMonks-approved HTML":


  • Posts are HTML formatted. Put <p> </p> tags around your paragraphs. Put <code> </code> tags around your code and data!
  • Titles consisting of a single word are discouraged, and in most cases are disallowed outright.
  • Read Where should I post X? if you're not absolutely sure you're posting in the right place.
  • Please read these before you post! —
  • Posts may use any of the Perl Monks Approved HTML tags:
    a, abbr, b, big, blockquote, br, caption, center, col, colgroup, dd, del, details, div, dl, dt, em, font, h1, h2, h3, h4, h5, h6, hr, i, ins, li, ol, p, pre, readmore, small, span, spoiler, strike, strong, sub, summary, sup, table, tbody, td, tfoot, th, thead, tr, tt, u, ul, wbr
  • You may need to use entities for some characters, as follows. (Exception: Within code tags, you can put the characters literally.)
            For:     Use:
    & &amp;
    < &lt;
    > &gt;
    [ &#91;
    ] &#93;
  • Link using PerlMonks shortcuts! What shortcuts can I use for linking?
  • See Writeup Formatting Tips and other pages linked from there for more info.