/doc/variant.objrefs.html

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  4. <title>PTypes: variant: object references</title>
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  10. <p><a href="../index.html"><img src="title-21.png" width="253" height="39" alt="C++ Portable Types Library (PTypes) Version 2.1" border="0"></a> 
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  13. <p class="hpath"><a href="index.html">Top</a>: <a href="basic.html">Basic types</a>: 
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  14. <a href="variant.html">variant</a>: Object references</p>
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  15. <p><br>
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  16. Variants can hold references to objects derived from <span class="lang">component</span>. 
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  17. PTypes performs reference counting, so that assigning variants containing object 
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  18. references can be considered safe: an object will only be destroyed when there 
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  19. are no more references left to it. If you want to control the destruction of an 
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  20. object 'manually', you can increment the reference count with <span class="lang">addref()</span> 
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  21. before assigning a reference to a variant (see <a href="unknown.html">unknown 
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  22. &amp; component</a>). In this case, each call to <span class="lang">addref()</span> 
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  23. should be balanced with a call to <span class="lang">release()</span>.</p>
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  24. <p>It should be noted that the reference counting mechanism has a potential flaw 
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  25. which may lead to memory leaks. Consider two objects containing variants with 
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  26. cross-referencing pointers to each other. The library can not keep track of such 
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  27. circular references, and an attempt to free one of the objects will result in 
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  28. destroying only one of them and leaving the other in the memory without any references 
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  29. to it. This is a known problem and can be solved by either eliminating circular 
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  30. references when designing data structures or by providing a complex memory 'garbage 
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  31. collector' which keeps track of all object references in the program.</p>
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  32. <p class="seealso">See also: <a href="unknown.html">unknown &amp; component</a>, 
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  33. <a href="variant.typecasts.html">Assignments and typecasts</a>, <a href="variant.arrays.html">Arrays</a>, 
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  34. <a href="variant.utils.html">Utilities</a> </p>
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  37. <a href="../index.html" class="ns">PTypes home</a>
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