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Sizeof empty struct is 0 byte in C but in C++ it is 1 byte. Why? What's the difference?
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Generally, it is 1 byte.
In c the behaviour of an empty structure is compiler dependent versus c++ where it is part of the spec (explanations here) C++ A class with an empty sequence of members and base class objects is an empty class.
The size of an empty class is not zero. It is 1 byte generally. It is nonzero to ensure that the two different objects will have different addresses.
The size of the entire structure is 8 bytes. On knowing the structured padding, it is easier to redesign or rewrite the structure.
In C its not correct, you cannot have a struct without a member in it.
C99 says,
If the struct-declaration-list contains no named members, the behavior is undefined.
However GCC allows you to have a no member struct with size being 0. G++ treats struct as if it has a single member of type char in it.
Look at this previous SO answering why in C++ the size is 1B.
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