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POIn assignment operator function, is array being memcpy implicitly
 

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  1. POIn assignment operator function, is array being memcpy implicitly
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    <p>OK. We know the following code cannot be compiled.</p> <pre><code>char source[1024]; char dest[1024]; // Fail. Use memcpy(dest, source, sizeof(source)); instead. dest = source; </code></pre> <p>But, the following code can be compiled and behave correctly.</p> <pre><code>class A { char data[1024]; }; A source; B dest; dest = source; </code></pre> <p>I was wondering, in operator assignment function, is array will be memcpy implicitly?</p> <p>The following are the complete test code.</p> <hr> <pre><code>#include &lt;cstdio&gt; #include &lt;memory&gt; class A { public: char data[1024]; }; int main() { { A source; A dest; // Initialization char *data = "hello world"; memcpy (source.data, data, strlen(data) + 1); printf ("source.data = %s\n", source.data); printf ("address source.data = %x\n", source.data); // Works! Does this in the operator assignment function, memcpy is // being performed implicitly on array. dest = source; printf ("dest.data = %s\n", dest.data); printf ("address dest.data = %x\n", dest.data); } { char source[1024]; char dest[1024]; // Initialization char *data = "hello world"; memcpy (source, data, strlen(data) + 1); printf ("source = %s\n", source); printf ("address source = %x\n", source); // '=' : left operand must be l-value // dest = source; // Works with memcpy. memcpy(dest, source, sizeof(source)); printf ("dest = %s\n", dest); printf ("address dest = %x\n", dest); } getchar(); } //RESULT : //source.data = hello world //address source.data = 12fb60 //dest.data = hello world //address dest.data = 12f758 //source = hello world //address source = 12f344 //dest = hello world //address dest = 12ef3c </code></pre>
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    1. COThere was a lot of discussion about why this is the case in [Why does C++ support memberwise assignment of arrays within structs but not generally?](http://stackoverflow.com/questions/3437110/why-does-c-support-memberwise-assignment-of-arrays-within-structs-but-not-gene)
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    2. COOpposed to std::string, eh?
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      1. USEric Towers
 

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