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copied!<p>It's going to be a bit of a guess why the const matters, but one can make a reasonable assumption.</p> <p>Variables with block scope, such as <code>result</code> can be allocated to a register or put on the stack. There are many factors that influence whether a register is used. It's quite possible that <code>const</code> matters, in this case. In the end, it's the compilers right to use what it thinks works best.</p> <p>Similarly, arguments to functions can be passed in registers or on the stack. As functions are often compiled seperately, their interface (i.e. declaration) dictates which argument goes where. printf(...) is a special case, as it can be called with different types arguments. As a result, what data ends up where will vary, and you need to tell printf(...) what to expect.</p> <p>Now when passing a variable to a function, the compiler usually has to copy it. From a register to the stack, one register to another, etcetera, there are quite a few variations possible. As I indicated, the source location may differ depending on the presence or absence of <code>const</code>.</p> <p>Now as it happens you pass the wrong format specifier to <code>printf(...)</code>, namely <code>%u</code> instead of <code>%ld</code>. This can cause printf(...) to look in the wrong place to get its data - perhaps in a register instead of the stack, or the other way around. Such an action can cause quite surprising results. <code>printf(...)</code> could for instance stumble across your uncopied <code>result</code>, or the random old values in some register. It seems that in the non-const case it happens to find the correct value (even though it might have found it in the wrong place), whereas in the const case <code>printf(...)</code> just finds garbage.</p>

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