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Add in va_list varargs workaround suggested by Antoine Mathys

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git-svn-id: https://swig.svn.sourceforge.net/svnroot/swig/trunk@13949 626c5289-ae23-0410-ae9c-e8d60b6d4f22
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William S Fulton 2012-12-07 07:38:24 +00:00
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36
Doc/Manual/Varargs.html
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@ -839,13 +839,13 @@ of type <tt>va_list</tt>. For example:
<div class="code"> <div class="code">
<pre> <pre>
int vfprintf(FILE *f, const char *fmt, va_list ap); int vprintf(const char *fmt, va_list ap);
</pre> </pre>
</div> </div>
<p> <p>
As far as we know, there is no obvious way to wrap these functions As far as we know, there is no obvious way to wrap these functions with
with SWIG. This is because there is no documented way to assemble the SWIG. This is because there is no documented way to assemble the
proper va_list structure (there are no C library functions to do it proper va_list structure (there are no C library functions to do it
and the contents of va_list are opaque). Not only that, the contents and the contents of va_list are opaque). Not only that, the contents
of a <tt>va_list</tt> structure are closely tied to the underlying of a <tt>va_list</tt> structure are closely tied to the underlying
@ -853,6 +853,36 @@ call-stack. It's not clear that exporting a <tt>va_list</tt> would
have any use or that it would work at all. have any use or that it would work at all.
</p> </p>
<p>
A workaround can be implemented by writing a simple varargs C wrapper and then using the techniques
discussed earlier in this chapter for varargs. Below is a simple wrapper for <tt>vprintf</tt> renamed so that
it can still be called as <tt>vprintf</tt> from your target language. The <tt>%varargs</tt>
used in the example restricts the function to taking one string argument.
</p>
<div class="code">
<pre>
%{
int vprintf(const char *fmt, va_list ap);
%}
%varargs(const char *) my_vprintf;
%rename(vprintf) my_vprintf;
%inline %{
int my_vprintf(const char *fmt, ...) {
va_list ap;
int result;
va_start(ap, fmt);
result = vprintf(fmt, ap);
va_end(ap);
return result;
}
%}
</pre>
</div>
<H2><a name="Varargs_nn9"></a>13.8 C++ Issues</H2> <H2><a name="Varargs_nn9"></a>13.8 C++ Issues</H2>