CODEWITHSUNDEEP
cpointers
K.H.A.J.A.S
K.H.A.J.A.S

Reputation: 516

What is the difference between an integer a and *(&a) ?

I am not getting the difference between an integer a and *(&a) ? I mean *(&a) returns the value contained in the address of a and it's the same as a , no? So why the use of pointers in this case?

Upvotes: 1

Views: 174

Answers (4)

Tom Karzes
Tom Karzes

Reputation: 24052

More to the point, you wouldn't normally write *(&a), or *&a. This could arise as a result of macros or something, but you would normally never actually write something like that explicitly. You can take it to extremes: *&*&*&*&*&*&a works just as well. You can try it for yourself:

#include <stdio.h>

int main()
{
    int     a = 123;
    int     b = *&*&*&*&*&*&a;

    printf("%d\n", b);

    return 0;
}

Upvotes: 0

haccks
haccks

Reputation: 106012

What is the difference between an integer a and *(&a) ?

No difference. int a; declares a as a variable of an int type. &a is the address of a is of type int *, i.e. pointer type and therefore it can be dereferenced. So, *(&a) will give the value of a.

Upvotes: 4

Abhineet
Abhineet

Reputation: 5389

Take this as an example,

int a = 1;
int *ptr = &a;

ptr points to some address in memory, and the address of ptr itself, is different in memory.

Now, take a look at below drawing,

// *ptr = *(&a) 
// Get the adress of `a` and dereference that address.
// So, it gives the value stored at `a`

memory address of        a -> 0x7FFF1234
value stored at          0x7FFF1234 = 1

memory address of        ptr -> 0x7FFF4321
value stored at          0x7FFF4321 = &a = 0x7FFF1234

                                           +-------+
           +------------>  0x7FFF1234 ---->|a = 1  |
           |                               +-------+
           |              +-----------------+ 
           |              | ptr =           |    
           +--*ptr<-------| 0x7FFF1234 [&a] |<--- 0x7FFF4321       
                          +-----------------+

So, there is no difference between both of them, i.e., int a and *(&a) are same.

Upvotes: 0

Blindy
Blindy

Reputation: 67380

As long as a is a variable, there's no difference, they're identical.

However, if you use that expression in a macro for instance, it will fail with a compiler error for temporary objects (*&(x+1)) or literals (*&5). Perhaps there's a reason for making that distinction in code.

Upvotes: 2

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