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<title>PTypes: variant: object references</title>
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<p class="hpath"><a href="index.html">Top</a>: <a href="basic.html">Basic types</a>: 
<a href="variant.html">variant</a>: Object references</p>
<p><br>
Variants can hold references to objects derived from <span class="lang">component</span>. 
PTypes performs reference counting, so that assigning variants containing object 
references can be considered safe: an object will only be destroyed when there 
are no more references left to it. If you want to control the destruction of an 
object 'manually', you can increment the reference count with <span class="lang">addref()</span> 
before assigning a reference to a variant (see <a href="unknown.html">unknown 
& component</a>). In this case, each call to <span class="lang">addref()</span> 
should be balanced with a call to <span class="lang">release()</span>.</p>
<p>It should be noted that the reference counting mechanism has a potential flaw 
which may lead to memory leaks. Consider two objects containing variants with 
cross-referencing pointers to each other. The library can not keep track of such 
circular references, and an attempt to free one of the objects will result in 
destroying only one of them and leaving the other in the memory without any references 
to it. This is a known problem and can be solved by either eliminating circular 
references when designing data structures or by providing a complex memory 'garbage 
collector' which keeps track of all object references in the program.</p>
<p class="seealso">See also: <a href="unknown.html">unknown & component</a>, 
<a href="variant.typecasts.html">Assignments and typecasts</a>, <a href="variant.arrays.html">Arrays</a>, 
<a href="variant.utils.html">Utilities</a> </p>
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