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    <p>The most likely reason for <code>m</code> being <code>0</code> in your snippet is because you assign <code>m</code> to have this value in the body of your if-statement, but since the code contains <em>undefined behavior</em> no one can say that for sure.</p> <hr> <h2>The likely story about passing a <code>short*</code> when scanf expects an <code>int*</code></h2> <p>Assuming <code>sizeof(short) = 2</code> and <code>sizeof(int) == 4</code>.</p> <p>When entering your main function the stack on which the variables reside would normally look something like the below:</p> <pre><code> _ |short int (a) : scanf will try to read an int (4 bytes). |_ 2 bytes : This part of memory will most |int (n) : likely be overwritten | :.. | |_ 4 bytes |int (m) | | |_ 4 bytes </code></pre> <p>When you read a <code>%d</code> (ie. an <code>int</code>) into the variable <code>a</code> that shouldn't affect variable <code>m</code>, though <code>n</code> will most likely have parts of it overwritten.</p> <hr> <h2>Undefined Behavior</h2> <p>Though it's all a guessing game since you are invoking what we normally refer to as "<em>undefined behavior</em>" when using your scanf statement.</p> <p>Everything the standard doesn't guarantee is UB, and the result could be anything. Maybe you will write data to another segment that is part of a different variable, or maybe you might make the universe implode.</p> <p>Nobody can guarantee that we will live to see another day when UB is present.</p> <hr> <h2>How to read a <code>short int</code> using <code>scanf</code></h2> <p>Use <code>%hd</code>, and be sure to pass it a <code>short*</code>.. we've had enough of UB for one night!</p>
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    1. CO+1, for posting this in Lounge<C++>
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    2. CO@IntermediateHacker You should +1 my little black ass for doing this: **[click here for incognito pron, we don't have cookies](http://chat.stackoverflow.com/rooms/10/loungec)** (it's a link to the SO chat room `Lounge<C++>`)
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    3. CO*Most answers in this thread are not far from being completely wrong!* is misleading and Incorrect, Almost every answer says it is **Undefined Behavior** and Once you say that any possible explanation of the after effect is at best a *likely guess*.So I am unable to understand what your Opening statement means.
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