type conversion in c programming

Question

https://www.onlinegdb.com/edit/r1CBB9EHO

#include<stdio.h>
int main()
{
    short int i = 10;
    char c = 'a';
    float  p = 3.0;
    short int s = i+c;

    printf("%d\n", sizeof(short int)); //size of short int is 2
    printf("%d\n", sizeof(char)); // size of char is 1
    printf("%d\n", sizeof(c+i)); /*why is size of (char+short int) is 4 and not 2.
    It should be 2 because char should be promoted to short int,
    and then the result of (short int + short int) should be short int whose size should be 2. */

    printf("%d", sizeof(s)); // though here it is 2 which is correct.


    return 0;


}

 

Comments

Why not do sizeof(c+c) ?

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https://wiki.sei.cmu.edu/confluence/display/c/INT02-C.+Understand+integer+conversion+rules

https://port70.net/~nsz/c/c11/n1570.html#6.3.1.1 

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Thanks for the link mate.

Answer 1

All operands of type char and short are converted to int before any operation.

That’s why sizeof(c+i) returns 4.

In the assignment operator the value of the RHS operand is converted to the type of the LHS operand.

That’s why sizeof(s) returns 2.

Comments

Thanks mate.

All data types having less rank than int are converted to int for operations.