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    <p>A lot depends on what type of argument you imagine your clients trying to pass. If they're passing int, and that's clearly big enough to hold the range of values you're going to use, then there's no practical advantage to using std::size_t - it won't enforce anything, and the way the issue manifests as an apparently huge number is simply more confusing.</p> <p>BUT - it is good to use size_t anyway as it helps document the expectations of the API.</p> <p>You clearly can't do a compile-time check for "> 0" against a run-time generated value, but can at least disambiguate negative inputs from intentional huge numbers ala</p> <pre><code>template &lt;typename T&gt; void f(T t) { if (!(t &gt; 0)) throw std::runtime_error("be positive!"); // do stuff with t, knowing it's not -1 shoehorned into size_t... ... } </code></pre> <p>But, if you are really concerned about this, you could provide overloads:</p> <pre><code>// call me please e.g. f(size_t(10)); void f(size_t); // unimplemented (and private if possible)... // "want to make sure you realise this is unsigned: call f(size_t) explicitly void f(int32_t); void f(int64_t); </code></pre> <p>...then there's a compile-time error leading to the comments re caller explicitly providing a size_t argument (casting if necessary). Forcing the client to provide an arg of size_t type is a pretty good way to make sure they're conscious of the issue.</p> <p>Rin's got a good idea too - would work really well where it works at all (depends on there being an signed int type larger than size_t). Go check it out....</p> <p>EDIT - demonstration of template idea above...</p> <pre><code>#include &lt;iostream&gt; template &lt;typename T&gt; void f(T t) { if (!(t &gt; 0)) std::cout &lt;&lt; "bad call f(" &lt;&lt; (int)t &lt;&lt; ")\n"; else std::cout &lt;&lt; "good f(" &lt;&lt; (int)t &lt;&lt; ")\n"; } int main() { f((char)-1); f((unsigned char)255); } </code></pre>
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    1. COthank you for your very interesting answer. I just can't make a sense out of your first example. What is it? is it a template function called f? if so what is the return type of it? And how am I suppose to understand (f > 0)? If you could please explain that to my murky brain I would be more than gratefull.
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    2. CO@There: sorry - left out the return type and the argument type! Careless. The idea's just that a template instantiation knows the type that the caller's actually passing in, so it can provide type-(and signed/unsigned is part of type)-aware verification. The `if (!(t>0) throw` just exits early if they's say called with int(-1), as the compiler still knows it's an int and won't confuse it with a legitimately huge size_t.
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    3. COsorry still cannot grasp the concept of (f > 0). How compiler will know what value is passed to f? Would you be able to explain that to me, please?
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