When I happen to revisit this slim dinosaur that is C I always have to look up a couple things - here they are for your convenience and mine.
First things first - wrong:
int *ptr = malloc(10 * sizeof (int));
int *ptr = malloc(10 * sizeof *ptr);
NO exceptions. A, yes, sizeof is a unary operator. Are parentheses needed ? Well, I always add them when nobody’s looking.