weird macros

gistfile1.c

#include <setjmp.h>
#include <stdio.h>

#define WHILE(while_expr) {                      \
        int jumped____;                          \
        jmp_buf redo_target____;                 \
        int restarted____;                       \
        restarted____ = setjmp(redo_target____); \
        jumped____ = 1;                          \
        while ((while_expr)||(jumped____=0)) {
#define UNTIL(until_expr) WHILE(!(until_expr))
#define DO
#define REDO longjmp(redo_target____, 1)
#define THEN } if (!jumped____) {
#define ELSE } else {
#define FINALLY } {
#define END } }

int main()
{
    int i=0, j=11, k=3;

    UNTIL (i == 10)
    DO
        printf("i: %d\n", i);

        if (i > j) {
            printf("Leaving loop\n");
            break;
        }
        else if (i == k) {
            k = j + 1;
            i = 0;
            printf("Restarting loop\n");
            REDO;
        }
        i++;
    THEN
        printf("Counted to end\n");
    ELSE
        printf("Exited loop early\n");
    FINALLY
        printf("And in both cases came here\n");
    END

    return 0;
}