Doubt on Pointer in C++

[richard36]

#include <iostream>
using namespace std;
class A{



};

int main(){


    A a;
    int x=sizeof(a);
    cout << "size is "<<x<<endl;
    return 0;
}

output: size is 1

and if i modify it to A *a then the size is 8


what could be the reason? any reply is appreciated

[laserlight]

*moved to C++ programming forum*

Read Stroustrup's answer to the FAQ: Why is the size of an empty class not zero?

[MutantJohn]

#include <iostream>
using namespace std;
class A{



};

int main(){


    A a;
    int x=sizeof(a);
    cout << "size is "<<x<<endl;
    return 0;
}

output: size is 1

and if i modify it to A *a then the size is 8


what could be the reason? any reply is appreciated

In addition to laser's link about why empty structures are at least 1 byte, you're printing out the size of a pointer on your system. This will return 8 for all data types. It's because on your system, addresses to data are stored with 8 bytes.

[Elysia]

This will return 8 for all data types. It's because on your system, addresses to data are stored with 8 bytes.

First and foremost, this is not true because all pointers are not guaranteed to be of the same size.
And you probably meant all pointer types.

[MutantJohn]

First and foremost, this is not true because all pointers are not guaranteed to be of the same size.
And you probably meant all pointer types.

Ah yes, I did (with regards to all pointer types).

And are you sure? All pointers won't be the same size? I've never heard that before. Do you have any sample code?

Edit : I googled it and it seems like only old or obscure compilers have varying pointer sizes.

Nevertheless, that is still a very important distinction so thank you anyway.

[Elysia]

And are you sure? All pointers won't be the same size? I've never heard that before. Do you have any sample code?

Do I have any code? Not really.
See c - Are all data pointers of the same size in one platform? - Stack Overflow.