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Code Issues Releases Wiki Activity

Added some advice regarding header files

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Klaus Schmidinger 2002-05-11 14:51:51 +02:00
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@ -183,6 +183,40 @@ its memory. You don't need to worry about the details behind all this.
<p> <p>
If your plugin requires additional source files, simply add them to your plugin's If your plugin requires additional source files, simply add them to your plugin's
source directory and adjust the <tt>Makefile</tt> accordingly. source directory and adjust the <tt>Makefile</tt> accordingly.
<p>
<!--X1.1.1--><table width=100%><tr><td bgcolor=red>&nbsp;</td><td width=100%>
Header files usually contain preprocessor statements that prevent the same
file (or rather its contents, to be precise) from being included more than once, like
<p><table><tr><td bgcolor=#F0F0F0><pre><br>
#ifndef __I18N_H
#define __I18N_H
...
#endif //__I18N_H
</pre></td></tr></table><p>
The example shown here is the way VDR does this in its core source files.
It takes the header file's name, converts it to all uppercase, replaces the
dot with an underline and preceedes the whole thing with two underlines.
The GNU library header files do this pretty much the same way, except that they
usually precede the name with only one underline (there are exceptions, though).
<p>
As long as you make shure that none of your plugin's header files will be named
like one of VDR's header files, you can use the same method as VDR. However,
if you want to name a header file like one that is already existing in VDR's
source (<tt>i18n.h</tt> would be a possible candidate for this), you may want
to make sure that the macros used here don't clash. How you do this is completely
up to you. You could, for instance, prepend the macro with a <tt>'P'</tt>, as in
<tt>P__I18N_H</tt>, or leave out the trailing <tt>_H</tt>, as in <tt>__I18N</tt>,
or use a completely different way to make sure a header file is included only once.
<p>
The 'hello' example that comes with VDR makes use of <a href="#Internationalization">internationalization</a>
and implements a file named <tt>i18n.h</tt>. To make sure it won't clash with VDR's
<tt>i18n.h</tt> it uses the macro <tt>_I18N__H</tt> (one underline at the beginning
and two replacing the dot).
<!--X1.1.1--></td></tr></table>
<hr><h2>Construction and Destruction</h2> <hr><h2>Construction and Destruction</h2>