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On 07/01/2011 03:04 AM, Frank Peters wrote: |
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> On Fri, 01 Jul 2011 02:44:36 +0300 |
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> Nikos Chantziaras<realnc@×××××.de> wrote: |
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> |
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>>> |
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>>> Your code is buggy, because you're breaking C's aliasing rules. You are |
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>>> not allowed to use a different pointer type to dereference a variable of |
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>>> a different type. Doing so results in undefined behavior. |
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>> |
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> |
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> Well, the error occurs only within the loop structure. If |
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> I manually "unroll" the loop using the same pointers there |
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> is no error when compiled with "O2." |
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> |
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> IOW, the problem is how the loop is optimized under -O2. |
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|
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When there's "undefined behavior", it really means just that: you cannot |
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make any assumptions about when the result is going to be correct and |
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when not. It might as well depend on whether it was raining yesterday. |
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