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    <p>use <code>std::stringstream</code></p> <pre><code>unsigned int x; std::stringstream ss; ss &lt;&lt; std::hex &lt;&lt; "fffefffe"; ss &gt;&gt; x; </code></pre> <p>the following example produces <code>-65538</code> as its result:</p> <pre><code>#include &lt;sstream&gt; #include &lt;iostream&gt; int main() { unsigned int x; std::stringstream ss; ss &lt;&lt; std::hex &lt;&lt; "fffefffe"; ss &gt;&gt; x; // output it as a signed type std::cout &lt;&lt; static_cast&lt;int&gt;(x) &lt;&lt; std::endl; } </code></pre> <p><strong>EDIT:</strong> C++11 update. In the new standard, there are a few new utility functions which you can make use of! specifically, there is a family of "string to number" functions (<a href="http://en.cppreference.com/w/cpp/string/basic_string/stol" rel="noreferrer">http://en.cppreference.com/w/cpp/string/basic_string/stol</a> and <a href="http://en.cppreference.com/w/cpp/string/basic_string/stoul" rel="noreferrer">http://en.cppreference.com/w/cpp/string/basic_string/stoul</a>). These are essentially thin wrappers around C's string to number conversion functions, but know how to deal with a <code>std::string</code></p> <p>So, the simplest answer for newer code would probably look like this:</p> <pre><code>std::string s = "0xfffefffe"; unsigned int x = std::stoul(s, nullptr, 16); </code></pre> <p><strong>NOTE:</strong> Below is my original answer, which as the edit says is not a complete answer. For a functional solution. Stick the code above the line :-).</p> <hr> <p><strong>EDIT:</strong> It appears that since <code>lexical_cast&lt;&gt;</code> is defined to have stream conversion semantics. Sadly, streams don't understand the "0x" notation. So both the <code>boost::lexical_cast</code> and my hand rolled one don't deal well with hex strings. The above solution which manually sets the input stream to hex will handle it just fine.</p> <p><a href="http://www.boost.org/doc/libs/1_39_0/libs/conversion/lexical_cast.htm" rel="noreferrer">Boost has some stuff</a> to do this as well, which has some nice error checking capabilities as well. You can use it like this:</p> <pre><code>try { unsigned int x = lexical_cast&lt;int&gt;("0x0badc0de"); } catch(bad_lexical_cast &amp;) { // whatever you want to do... } </code></pre> <p>If you don't feel like using boost, here's a light version of lexical cast which does no error checking:</p> <pre><code>template&lt;typename T2, typename T1&gt; inline T2 lexical_cast(const T1 &amp;in) { T2 out; std::stringstream ss; ss &lt;&lt; in; ss &gt;&gt; out; return out; } </code></pre> <p>which you can use like this:</p> <pre><code>// though this needs the 0x prefix so it knows it is hex unsigned int x = lexical_cast&lt;unsigned int&gt;("0xdeadbeef"); </code></pre>
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    1. POC++ convert hex string to signed integer
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    1. COWhen I use that method, I end up with an integer value of 152144602
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    2. CORemove unsigned, and it should work as advertised.
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    3. CO@jmanning2k, yea, it's weird that both boost and my lexical_cast barf on hex strings (even with the 0x prefix) if i don't put std::hex in the string.
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