Why the prgram crashes when somebody tries to add two pointers?

[malojinaik]

Why the prgram crashes when somebody tries to add two pointers.Is C language built like that or adding two pointers will cause the problem somehow?Please answer to this I am bit confused.

[JosAH]

@malojinaik
You can't add two pointers; you can add integers to pointers or you can subtract two pointers.

kind regards,

Jos

[donbock]

@malojinaik
Do you mean that you tried to add two pointer values together (like pab below)?

int a;
int b;
int *pa = &a;        // The value of pa is the address of a.
int *pb = &b;        // The value of pb is the address of b.
 
int *pab = pa + pb;  // What does this mean?
int c = *pab;        // !!! Danger !!!
 

I suppose you can add two pointer values together, but to what end? What do you think that is going to accomplish?

Suppose the address of a is 0x0200 (that's the value of pa) and the address of b is 0x0204 (that's the value of pb). In that case, the value of pab is 0x0404. What is stored there? What happens when I try to assign a value to c? Either address pab is outside the bounds of my program and we crash with an access error; or worse, some arbitrary garbage value is pulled from somewhere in my program and written to c.

[JosAH]

@donbock
No you can't: the compiler (neither C nor C++) won't let you unless you explicitly cast at least one of the pointer values to an int. As you showed already it doesn't make sense.

kind regards,

Jos