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PODifferences between the C++ and the Java object model
 

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    <ol> <li><p>In Java it is very easy to serialize objects. In C++ it is only safe(?) to <code>memcpy</code> objects as long as they are like C structs (no polymorpism). In C++, <strong>if the compiler is able to generate the default (trivial) copy constructor then why can't it generate code for automatic serialization?</strong></p></li> <li><p><del>In Java, only static functions and data members are reachable from the ctor. In C++ I can happily use the non-static members and functions from the ctor.</del></p></li> <li><p>In Java, I can initialize data members inline, in the class. In C++ it is a compile error.</p></li> <li><p>In Java I can initialize <code>final</code> members in the ctor. In C++ I have to do the initialization of the <code>const</code> members in the initialization list. <strong>In C++, when control reaches the body of the ctor, all the members ctor has run, right?</strong></p></li> <li><p>In Java a ctor can call another ctor. In C++ we cannot do that.</p></li> <li><p>In Java, the <code>this</code> is not valid until after the ctor returns (escape of the <code>this</code> reference, a bug in multi-threading). When is <code>this</code> valid in C++? The <code>this</code> can easily escape both in C++ and in Java: <strong>registering a not yet constructed object to Listeners in the ctor</strong> (observer pattern).</p></li> <li><p>In Java, I cannot make a public function of the base class private in the derived class. I was shocked to see that in C++ is OK and even useful.</p></li> </ol> <p>Could anyone give a short explanation for these differences?</p> <p><strong>Update.</strong> Trying to collect the answers got so far.</p> <ol> <li><p>Boost has some serialization-like support. (Tony)</p></li> <li><p>Even though I messed up this point, Alf P. Steinbach gave an interesting example.</p></li> <li><p>C++0x will support much more practical initialization than C++98. (Alf P. Steinbach) #3 will be legal in C++0x (Ken Bloom)</p></li> <li><p>The data members declared in the constructor's own class are guaranteed to have been fully constructed by the time the constructor's {body} starts executing. (c++-faq-lite)</p></li> <li><p>C++0x will allow constructors to call other peer constructors (Wikipedia, C++0x)</p></li> <li><p>C++03 considers an object to be constructed when its constructor finishes executing (Wikipedia).</p></li> <li><p>Things like access control have little to do with the object model: that's a feature of the access control system which is a compile time feature. (Yttrill)</p></li> </ol>
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    1. CONo, it's not even safe to `memcpy` them then. (Also, a ctor can call another ctor in C++0x).
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    2. CO#3 will be legal in C++0x
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    3. COOh, and Java doesn't have ctors--they have constructors. In Java they prefer to spell everything out rather than use cryptic abbreviations--another philosophy difference.
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