Need some clarification regarding casting in C

Question

I was just reading about the bad practice of casting the return value of malloc. If I understood correctly, it is absolutely legal to leave the cast as it is do

Answer 1

The admonition against casting the result of malloc() is a special case, due to C implicitly typing the result of previously undeclared functions to int (which IINM is disallowed as of C99).

Generally, you want to limit the use of explicit casts as much as possible; the only time you need to use one is if you're trying to assign a value of one type to a variable of an incompatible type (e.g., assign a pointer value to an int variable or vice versa). Since void * is compatible with every other pointer type, no explicit cast is needed. However, if you're trying to assign a value of type int * to a variable of type struct foo *, an explicit cast is required. If you find yourself assigning values of incompatible types a lot, then you may want to revisit your design.