#include <stdio.h>
 
 
#define BEGIN switch (ctx->state) { \
                        case 0:
 
#define YIELD(val) do { \
                        ctx->state = __LINE__;   \
                        return val;         \
                        case __LINE__:        \
                        ;                   \
                        } while (0)
 
#define END }
 
typedef struct{
    int state;	
    int i;
}  Ctx;
 
int foo(Ctx* ctx)
{
    BEGIN;
        while (1) {
        	printf("foo suspending...\n");
        	YIELD(++ctx->i);
        	printf("foo resumed\n");
        }
    END;
    return 0;
} 
 
int main()
{
    int i=0;
 
    Ctx t0 = {0,1};
    while (i = foo(&t0)) {
        printf("val: %d\n", i);
        if (i > 10) {
        	printf("enough\n");
        	break; // ideone can't run program indefinitely
        }
    } 
 
    return 0;
}

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