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POworst that can happen if i don't obey the stateless custom allocators dogma?
 

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  1. POworst that can happen if i don't obey the stateless custom allocators dogma?
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    <p>I need to create a custom allocator for std:: objects (particularly and initially for std::vector) but it might eventually come to use others</p> <p>The reason I need to create a custom allocator is that I need to track allocated (heap &amp; stack) resources by individual components of the application (<em>this is an inherent feature of the application</em>). I will need the custom allocator to monitor the heap portion of the resources, so it is essential that I'm able to pass to the std::vector constructor something like</p> <pre><code>trackerId idToTrackUsage; myAlloca&lt;int&gt; allocator(idToTrackUsage); vector&lt;int&gt; Foo( allocator ); </code></pre> <p>However, after reading a bit I found this little bomb about the STL / C++ standard (see references) saying that all allocator instances of a given type should be equivalent (that is that == should return true for any two instances) and, most terminal; any allocator should be able to deallocate memory allocated by any other instance (that is, without having a way to know what that other instance might be). In short, allocators cannot have state.</p> <p>So I'm trying to find the best way around this. Any clever ideas? I really really REALLY don't want to have to keep a custom version of std::vector around.</p> <p>EDIT: i read about scoped allocators for c++0x on <a href="http://www2.research.att.com/~bs/C++0xFAQ.html#scoped-allocator" rel="noreferrer">http://www2.research.att.com/~bs/C++0xFAQ.html#scoped-allocator</a> but i couldn't really get far into understanding how this applies to my problem. If anyone thinks c++0x alleviates this problem, please comment</p> <p>References:</p> <p><a href="http://en.wikipedia.org/wiki/Allocator_(C%2B%2B)" rel="noreferrer">Allocator C++ article in Wikipedia</a></p> <p><a href="http://www.codeguru.com/Cpp/Cpp/cpp_mfc/stl/article.php/c4079/" rel="noreferrer">Some random further reading courtesy of Google</a></p>
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    1. COBy the way, somewhat related, but I seem to recall there being significant changes to the allocator model in C++0x. Anyone know anything about this? (Or was this only before Concepts got removed?)
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    2. COi read about that on http://www2.research.att.com/~bs/C++0xFAQ.html#scoped-allocator but i couldn't really get far into understanding how this applies to my problem. (will update post with this)
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