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分类: C/C++

2010-06-13 00:45:27

I was wondering what could be the size of an object of an empty class. It surely could not be 0 bytes since it should be possible to reference and point to it like any other object. But, how big is such an object?

I used this small program:

#include 
using namespace std;

class Empty {};

int main()
{
   
Empty e;
    cerr
<< sizeof(e) << endl;
   
return 0;
}

The output I got on both Visual C++ and Cygwin-g++ compilers was 1 byte! This was a little surprising to me since I was expecting it to be of the size of the machine word (32 bits or 4 bytes).

Can anyone explain why the size of 1 byte? Why not 4 bytes? Is this dependent on compiler or the machine too? Also, can someone give a more cogent reason for why an empty class object will not be of size 0 bytes?

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