gistfile1.txt

 * if (x) {
 *     block = ^{ printf("true\n"); };
 * } else {
 *     block = ^{ printf("false\n"); };
 * }
 * block(); // unsafe!!!
 *
 * What is happening behind the scenes:
 *
 * if (x) {
 *     struct Block __tmp_1 = ...; // setup details
 *     block = &__tmp_1;
 * } else {
 *     struct Block __tmp_2 = ...; // setup details
 *     block = &__tmp_2;
 * }
 *
 * As the example demonstrates, the address of a stack variable is escaping the
 * scope in which it is allocated. That is a classic C bug.