When a contract becomes void, under the Indian Contract Act, 1872?

According to Section 2(g) of the Indian Contract Act, 1872, an agreement not enforceable by law is said to be void. Further, as per Section 2(j) of the Indian Contract Act, 1872 a contract which ceases to be enforceable by law becomes void when it ceases to be enforceable. A contract becomes void when, by reason of some event which the promisor could not prevent, the performance of the contract becomes impossible, e.g., by destruction of the subject-matter of the contract after the formation of the contract. A contract becomes void by reason of subsequent illegality. A in India agrees to supply goods to B in Pakistan. After the formation of the contract war breaks out between India and Pakistan and the supply of goods to Pakistan is prohibited by legislation. The contract becomes void. A contingent contract to do or not do to anything if an uncertain future event happens becomes void if the event becomes impossible.