sizeof(struct) vs. sizeof(class)

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Original post by Qoy
The extra 4 bytes is a pointer to the vtable. This will only be there if your class has virtual functions.

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Original post by mkaltner
Darn virtual deconstructor. =)

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Original post by Anonymous Poster
Stoffel: You''re only partially correct. A struct in C++ is handled as a class with Defualt Public members... a struct in C is a struct that cannot contain member functions, but only data members. Just because MSVC handles structs as classes, doesn''t make it true for everything ;o).

Billy

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Original post by Stoffel
...but you cannot inherit classes from structs and vice versa...

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struct Packet
{
DWORD PacketID;
};
struct ChatPacket : public Packet
{
WORD wLength;
char* szChatter;
};

struct IMyInterface
{
virtual void DoSomething()=0;
};

class CMyObject : public IMyInterface
{
public:
virtual void DoSomething() {}

};

//don't think I've tried this:

class Stuff
{
int morestuff;
};
struct Zoid : public Stuff
{
};

class SeemsToWork : Zoid
{
int yetmorecrap;
};
    

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There is one other slight difference, and I''m not really sure why it is (probably because of the default access), but you cannot inherit classes from structs and vice versa, nor can you forward-declare a class which is actually a struct nor vice-versa. I think this just annoys me more than anything (especially the latter).

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class CB
{
};

struct CD : public CB
{
};

struct SB
{
};

class SD : public SB
{
};

int main(int argc, char* argv[])
{
	CB cb;
	CD cd;
	SB sb;
	SD sd;
}
  

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Original post by kupps
what''s the point to using structs in c++?

if the only difference between a class and a struct is the default access method and u should be declaring the access method anyway, why not just use classes?

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struct CWaveFormat : WAVEFORMATEX
{
CDQuality();
RadioQuality();
//...
}