# c questions

Question

#define cube(x) x*x*x
main(){
int a=3,b;
b=cube(a++);
printf("% d % d",a,b);
}

Answer 1

#define cube(x) x*x*x 
main(){ 
int a=3,b; 
b=cube(a++); 
printf("%d %d",a,b); 
}

cube(3++) 

a++ * a++ * a++

++ (postfix) has higher precedence and associativity is left to right

(a++) * (a++) * (a++)

first leftmost a++ is calculated but non-modified value will be returned. So now a = 4 but 3 is returned

3 * (a++) * (a++)

now second a++ is calculated but non-modified value will be returned. So now a = 5 but 4 is returned

3 * 4 * (a++)

last a++ is calculated but non-modified value will be returned. So now a = 6 but 5 is returned

$3 * 4 * 5 = 60$

so b = 60 and a = 6

Output : $6 \ 60$

Edit : As Shaik mentioned in comments a++ * a++ * a++ is undefined. So order of execution of all 3 (a++) is not defined. Still answer won't change and will be 6 60. Answer is Undefined Behavior if there is an option "Undefined Behavior ".

Comments

Shaik yes you are right but still answer will not change. whichever a++ executes first answer will still be 60. If options contain Undefined behaviour i'll go for that but if it doesnot then  6 60

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  but if it doesnot then  6 60

b = a++ * a++ * a++ ;

b = 3*3*3 ===> b=27, right ?

But Discussion on this question is waste of our time due to in GATE, they never ask questions which lead to undefined behaviour.

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b = 3*3*3 ===> b=27, right ?

not possible but yes no point of discussion