Question

int a=5;
printf("%d %d %d\n",a++,a++,++a);

Output on Gcc :
7 6 8

Can someone please explain the answer.
I apologize if this question has been repeated but i wasn’t able to find it.

Thanks!!

Answer 1

The behaviour is undefined because there are no sequence points between the increment operators.

Explaining why the code does what it does is a pointless exercise. You should not write code that has undefined behaviour, even if it appears to work for you.

To address the point raised in the comments: It is true that the comma operator acts as a sequence point, however the comma here is not a comma operator. From Wikipedia:

The use of the comma token as an operator is distinct from its use in function calls and definitions, variable declarations, enum declarations, and similar constructs, where it acts as a separator.