How the number of byte required for string representation is calculated

I am not sure how LEN(LONG_MAX) prints 19, it should be 8 only.

#include <stdio.h>
#include <stdlib.h>
#include <limits.h>

#define STRING(x) #x
#define LEN(x) ((int)sizeof(STRING(x)) - (int)1)

int main()
{
    printf("%d\n",LEN(LONG_MAX));
    return 0;
}

>Solution :

It seems in the used by you system sizeof( long ) is equal to 8.

In this case the value of LONG_MAX is 9223372036854775807. That is the number contains 19 digits.

Due to this macro

#define STRING(x) #x

the value is converted to the string literal "9223372036854775807".

String literals are stored as character arrays with trailing terminating zero character '\0'. So sizeof( "9223372036854775807" ) is equal to 20 (19 plus one for the terminating zero character '\0' of the string literal).

As a result the whole expression produced by this macro

#define LEN(x) ((int)sizeof(STRING(x)) - (int)1)

is equal to 19.