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    <p>Basically you are right in the sense that since you are accessing an int * pointer, this will fetch 4 bytes instead of the only 2 reserved for 's' storage and the resulting content won't be a perfect reflection of what 's' really means.</p> <p>However this most likely won't crash since 's' is located on the stack so depending on how your stack is laid out at this point, you will most likely read data pushed during the 'main' function prologue... </p> <p>See for a program to crash due to invalid read memory access, you need to access a memory region that is not mapped which will trigger a 'segmentation fault' at the userworld level while a 'page fault' at the kernel level. By 'mapped' I mean you have a known mapping between a virtual memory region and a physical memory region (such mapping is handled by the operating system). That is why if you access a NULL pointer you will get such exception because there is no valid mapping at the userworld level. A valid mapping will usually be given to you by calling something like malloc() (note that malloc() is not a syscall but a smart wrapper around that manages your virtual memory blocks). Your stack is no exception since it is just memory like anything else but some pre-mapped area is already done for you so that when you create a local variable in a block you don't have to worry about its memory location since that's handled for you and in this case you are not accessing far enough to reach something non-mapped.</p> <p>Now let's say you do something like that:</p> <pre><code>short s = 10; int *i = (int *)&amp;s; *i = -1; </code></pre> <p>Then in this case your program is more likely to crash since in this case you start overwriting data. Depending on the data you are touching the effect of this might range from harmless program misbehavior to a program crash if for instance you overwrite the return address pushed in the stack... Data corruption is to me one of the hardest (if not the hardest) bugs category to deal with since its effect can affect your system randomly with non-deterministic pattern and might happen long after the original offending instructions were actually executed.</p> <p>If you want to understand more about internal memory management, you probably want to look into <a href="http://en.wikipedia.org/wiki/Virtual_memory" rel="nofollow">Virtual Memory Management</a> in Operating System designs.</p> <p>Hope it helps,</p>
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