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PO'typeid' versus 'typeof' in C++
 

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    <p>I am wondering what the difference is between <code>typeid</code> and <code>typeof</code> in C++. Here's what I know:</p> <ul> <li><p><code>typeid</code> is mentioned in the documentation for <a href="http://www.cplusplus.com/reference/typeinfo/type_info/" rel="noreferrer">type_info</a> which is defined in the C++ header file <a href="http://www.cplusplus.com/reference/typeinfo/?kw=typeinfo" rel="noreferrer">typeinfo</a>.</p></li> <li><p><code>typeof</code> is defined in the GCC extension for C and in the C++ <a href="http://en.wikipedia.org/wiki/Boost_C%2B%2B_Libraries" rel="noreferrer">Boost</a> library.</p></li> </ul> <p>Also, here is test code test that I've created where I've discovered that <code>typeid</code> does not return what I expected. Why?</p> <p><strong>main.cpp</strong></p> <pre><code>#include &lt;iostream&gt; #include &lt;typeinfo&gt; //for 'typeid' to work class Person { public: // ... Person members ... virtual ~Person() {} }; class Employee : public Person { // ... Employee members ... }; int main () { Person person; Employee employee; Person *ptr = &amp;employee; int t = 3; std::cout &lt;&lt; typeid(t).name() &lt;&lt; std::endl; std::cout &lt;&lt; typeid(person).name() &lt;&lt; std::endl; // Person (statically known at compile-time) std::cout &lt;&lt; typeid(employee).name() &lt;&lt; std::endl; // Employee (statically known at compile-time) std::cout &lt;&lt; typeid(ptr).name() &lt;&lt; std::endl; // Person * (statically known at compile-time) std::cout &lt;&lt; typeid(*ptr).name() &lt;&lt; std::endl; // Employee (looked up dynamically at run-time // because it is the dereference of a pointer // to a polymorphic class) } </code></pre> <p><strong>output:</strong></p> <pre class="lang-none prettyprint-override"><code>bash-3.2$ g++ -Wall main.cpp -o main bash-3.2$ ./main i 6Person 8Employee P6Person 8Employee </code></pre>
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    1. COIn what way do you think your code doesn't print the right type names? It looks good to me. The actual string returned by `name()` is implementation-defined. It doesn't have to be a valid C++ identifier name, just *something* that uniquely identifies the type. Looks like your implementation uses the compiler's general name-mangling scheme.
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    2. COThanks Rob! I was expecting those exactly same as type names as I saw in en.wikipedia.org/wiki/Typeid. What can name-mangling do here?
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