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POCout not printing number
 

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    <h2>Issue</h2> <p>I'm getting no output from a simple cout, whereas a printf will always print the number:</p> <pre><code>std::cout &lt;&lt; variableuint8; // prints nothing printf("%u", variableuint8); // prints the number </code></pre> <p>I've never run into this behavior before, and while I have a work around I would like to understand it.</p> <h2>Context:</h2> <p>Yay, pointers. So it may be a little more involved than as stated. Here's the context - I don't think it should matter, by the time cout and printf get the info it's dereferenced to a simple unsigned char. This is probably more information than needed to resolve the issue, but I wanted to be complete on the off chance that it was relevant.</p> <pre><code>typedef unsigned char UInt8; typedef unsigned short UInt16; typedef struct{ UInt8 len; // some other definitions. sizeof(DeviceNotification) &lt;= 8 }DeviceNotification; UInt8 somerandomdata[8]; DeviceNotification * notification; notification = (DeviceNotification *) somerandomdata; std::cout &lt;&lt; "Len: (" &lt;&lt; notification-&gt;len &lt;&lt; ")\n"; printf("Len: (%u)\n", notification-&gt;len); </code></pre> <p>The random data is initialized elsewhere. For this output, the first byte in the array is 0x08:</p> <h3>Output:</h3> <pre><code>Len: () Len: (8) </code></pre> <h2>Environment</h2> <ul> <li>Development machine: <ul> <li>OS X 10.6.8</li> <li>Compiler LLVM 1.7</li> <li>Xcode 3.2.6</li> </ul></li> <li>Test machine: <ul> <li>OS X 10.6.8</li> </ul></li> </ul>
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    1. USAnton Korobeynikov
    1. USAdam Davis
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    1. COI just wanna ask is the following line defined in C++? ` notification = (DeviceNotification *) somerandomdata;` doesn't this line invoke undefined behavior if the alignment is not the required alignment of `DeviceNotification`?
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      1. USAraK
    2. CO@AraK These are running on x86, which allows unaligned memory accesses. They may be slower, as they may require two reads of the memory bus to get a value that is split across the boundary, but it works just fine. You can perform some experiments to demonstrate this - if you do, let us know if there is a speed difference.
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      1. USAdam Davis
    3. COThanks, that is interesting. It would be nice to write such a micro-benchmark.
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