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    <p><strong>Crashing</strong> is normally caused by an illegal instruction, e.g. accessing invalid memory, dividing by zero, etc. Usually this manifests itself as a well-known exception which is handled by the operating system.</p> <p><strong>Hanging</strong> can be broken up into 2 fairly high level categories:</p> <ul> <li><strong>Deadlock</strong>, usually caused by 2 threads competing for a resource, each requiring a resource held by the other thread to be released. A common cause of this is acquiring multiple locks in inconsistent orders within multiple threads, leading to the common <a href="https://stackoverflow.com/questions/1892619/threads-and-simple-dead-lock-cure/1892640#1892640">ABBA deadlock pattern</a> (and no this has nothing to do with Swedish pop music).</li> <li><strong>Livelock</strong>, which means that the code is still actively running, but you have reached a state that you cannot leave. For example: <ul> <li>The state of 2 processes/threads keep changing, never reaching an end condition</li> <li>A <em>while loop</em> where the exit condition will never be satisfied, or an <em>indefinite loop</em> (although this is stretching the definition of "livelock").</li> </ul></li> </ul> <p><em>Update based on question comment</em></p> <blockquote> <p>@Pop, Kristo: Am actually checking on a code that hangs but I see some problems on memory leak. But I'm not really sure if memory leak causes a program to hang. – jasonline</p> </blockquote> <p>A memory leak can cause a program to crash, but this depends on various factors:</p> <ul> <li>Size of leak</li> <li>Frequency of leak</li> <li>Lifetime of application</li> </ul> <p>Memory leaks may result in 2 bad things - a continual increase in memory usage by the process, and memory fragmentation. Both of these can result in failure to allocate memory down the line, if the OS cannot provide a contiguous block of memory.</p> <p>In C++, if the <code>new</code> operator fails to allocate memory, a <code>std::bad_alloc</code> exception will be thrown. This will most likely be caught by the OS, resulting in a crash (unless you have written a specific handler in your application for this exception, and are able to handle it more gracefully).</p>
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    1. COAnd the major difference between crashing and hanging is that crashing typically terminates the process, while hanging continues the process with no noticeable progress.
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    2. CODav: Yes, I understand the effects but what I would like to know more are their causes.
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