sizeof implementation

[Debajyoti Sarma]

How to implement sizeof operator in C ?
cases
1. int i=0; sizeof(i)=4 ...i.e size of variables
2. sizeof(int)=4 ...i.e size of datatypes
3. struct t
{
int a;
char c;
}p;
sizeof(p)=5 ....i.e it should work for user
define data types
sizeof(t)=5

Function is more preferable than macro.

 

[Eric Sosman]

How to implement sizeof operator in C ?

The same way you implement the `+' operator: It's the
compiler's business.

[...]
Function is more preferable than macro.

Nonsense.

 

[Nick Keighley]

How to implement sizeof operator in C ?
cases
1. int i=0; sizeof(i)=4         ...i.e size of variables
2. sizeof(int)=4                 ...i.e size of datatypes
3. struct t
   {
   int a;
   char c;
   }p;
    sizeof(p)=5                  ....i.e it should work for user
define data types
    sizeof(t)=5

Function is more preferable than macro.

the correct answer is "sizeof is a built in operator of a C
implementaion. In general it cannot be implemented in standard C
code". That's *why* they built it in!

But to do your homework consider the result of running a program
containign code like this

int i,
int *pi = &i;
printf ("%p %p\n", pi, pi + 1);