C言語用コルーチン。マイクロスレッドとかファイバーとかそんなやつ。Arduino用に極力シンプルに実装。gccのラベル拡張使ってるからgcc専用。実行結果：fiber test0 0 1 1 1 1 2 2 2 3 3 4 4 5 9

fiber.h

#ifndef FIBER_H
#define FIBER_H

#define FIBER_NEST_ENABLE 1

typedef void* fiber_t;

#define FIBER_INIT	{ ((void*)0) }
#define FIBER_LINE2(x)	FIBER_LINE_ ## x
#define FIBER_LINE(x)	FIBER_LINE2(x)

#if FIBER_NEST_ENABLE
static fiber_t	__fb_softstack[8];
static fiber_t*	__fb_sp = __fb_softstack;
#define __fb_return__	(*(__fb_sp - 1))
#define __fb_current__	(*(__fb_sp - 0))
#define fiber_run(fb)						\
  for(*__fb_sp++ = &&FIBER_LINE(__LINE__), *__fb_sp = (fb)	\
	;(fb) != &&FIBER_LINE(__LINE__)				\
	;(fb) = &&FIBER_LINE(__LINE__), __fb_sp--)		\
    if(__fb_current__) {					\
      goto *__fb_current__;					\
      FIBER_LINE(__LINE__):					\
	(fb) = __fb_current__;					\
	__fb_sp--;						\
	break;							\
    }								\
    else
#else
static fiber_t	__fb_current__;
static fiber_t	__fb_return__;
#define fiber_run(fb)						\
  __fb_current__ = (fb);					\
  (fb) = __fb_return__ = &&FIBER_LINE(__LINE__);		\
  if(__fb_current__) {						\
    goto *__fb_current__;					\
    FIBER_LINE(__LINE__):					\
      (fb) = __fb_current__;					\
  }								\
  else
#endif

#define yield()					\
  do {						\
    __fb_current__ = &&FIBER_LINE(__LINE__);	\
    goto *__fb_return__;			\
    FIBER_LINE(__LINE__):			\
      ;						\
  } while(0);

#define wait_until(cond)			\
  while(!(cond)) {				\
    yield();					\
  }

#define fiber_init(fb)				\
  do {						\
    (fb) = FIBER_INIT;				\
  } while (0)

#endif

fiber_test.c

#include <stdio.h>
#include "fiber.h"

fiber_t fb0 = FIBER_INIT;
fiber_t fb1 = FIBER_INIT;
fiber_t fb2 = FIBER_INIT;
fiber_t fb3 = FIBER_INIT;
fiber_t fb4 = FIBER_INIT;
fiber_t fb5 = FIBER_INIT;
fiber_t fb6 = FIBER_INIT;

int main(int argc, char *argv[])
{
	int c = 0;

	do {
		fiber_run(fb0) {
			printf("fiber test\n");
		}

		fiber_run(fb1) {
			printf("%c\n", c + '0');
			yield();
		}

		fiber_run(fb2) {
			yield();
			printf(" %c\n", c+'0');
		}

		fiber_run(fb3) {
			yield();
			printf("  %c\n", c+'0');
			yield();
			printf("  %c\n", c+'0');
			yield();
		}

		fiber_run(fb4) {
			do {
				printf("   %c\n", c+'0');
				yield();
			} while(c < 5);
		}

#if FIBER_NEST_ENABLE
		fiber_run(fb5) {
			do {
				yield();
				printf("    %c\n", c+'0');

				fiber_run(fb6) {
					wait_until(c == 9);
					printf("     %c\n", c+'0');
				}

			} while(1);
		}
#else
		fiber_run(fb5) {
			do {
				yield();
				printf("    %c\n", c+'0');
			} while(c < 5);
		}

		fiber_run(fb6) {
			wait_until(c == 9);
			printf("     %c\n", c+'0');
		}
#endif
	} while(c++ < 10);
}