순수 C로 짠 Garbage Collector

struct linked_list {
	void *elem;
	struct linked_list *next;
};
 
#define ITERATOR(LIST_NAME) _iter_##LIST_NAME
 
#define DECLARE_LIST(NAME) struct linked_list *NAME, *ITERATOR(NAME)
 
#define INITIALIZE_LIST(NAME) \
NAME = (struct linked_list *)malloc(sizeof(struct linked_list)); \
NAME->elem = NULL; \
NAME->next = NULL; \
ITERATOR(NAME) = NAME
 
#define PUSH(TYPE, X, LIST) \
do { \
	ITERATOR(LIST) = ITERATOR(LIST)->next = (struct linked_list *)malloc(sizeof(struct linked_list)); \
	ITERATOR(LIST)->elem = malloc(sizeof(TYPE)); \
	*(TYPE *)ITERATOR(LIST)->elem = X; \
	ITERATOR(LIST)->next = NULL; \
} while (0)
 
#define DESTROY_LIST(LIST) \
do { \
	struct linked_list *l; \
	ITERATOR(LIST) = LIST; \
	do { \
		l = ITERATOR(LIST)->next; \
		free(ITERATOR(LIST)->elem); \
		free(ITERATOR(LIST)); \
	} while ((ITERATOR(LIST) = l) != NULL); \
} while (0)

#include "linked_list.h"
 
#define DECLARE_GC(NAME) \
DECLARE_LIST(NAME); \
static void _throw_away_##NAME() { \
	ITERATOR(NAME) = NAME; \
	do { \
		free(ITERATOR(NAME)->elem == NULL ? NULL : *(void **)ITERATOR(NAME)->elem); \
	} while ((ITERATOR(NAME) = ITERATOR(NAME)->next) != NULL); \
	DESTROY_LIST(NAME); \
}
 
#define INITIALIZE_GC(NAME) INITIALIZE_LIST(NAME)
 
#define GC_ALLOC(TYPE, TARGET, LEN, GC_NAME) \
do { \
	TARGET = (TYPE *)malloc((LEN) * sizeof(TYPE)); \
	PUSH(void *, TARGET, GC_NAME); \
} while (0)
 
#define GC_FREE(NAME) _throw_away_##NAME()

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <limits.h>
#include <time.h>
#include "garbage_collector.h"
 
struct vector {
	int *row;
	int len;
};
 
void run_test(unsigned num_tests);
char *rand_str(unsigned max_len);
char *concat(const char *str_1, const char *str_2);
struct vector rand_vector(unsigned len);
struct vector add_vector(const struct vector v_1, const struct vector v_2);
void print_vector(struct vector v);
 
DECLARE_GC(gc);
enum { STR_LEN_MAX = 20, VECTOR_LEN = 8, NUM_TESTS = 1000 };
 
int main() {
	INITIALIZE_GC(gc);
	srand(time(NULL));
 
	run_test(NUM_TESTS);
 
	GC_FREE(gc);
	return 0;
}
 
void run_test(unsigned num_tests) {
	char *str[2];
	struct vector v[2];
	int i;
 
	for (i = 0; i < num_tests; i++) {
		printf("TEST %d\n\n", i + 1);
		str[0] = rand_str(STR_LEN_MAX);
		str[1] = rand_str(STR_LEN_MAX);
		printf("%s + %s = %s\n\n", str[0], str[1], concat(str[0], str[1]));
		v[0] = rand_vector(VECTOR_LEN);
		v[1] = rand_vector(VECTOR_LEN);
		printf("  ");
		print_vector(v[0]);
		printf("\n+ ");
		print_vector(v[1]);
		printf("\n= ");
		print_vector(add_vector(v[0], v[1]));
		puts("\n\n");
	}
}
 
char *rand_str(unsigned max_len) {
	char *str;
	int len;
	int i;
 
	len = rand() % max_len + 1;
	GC_ALLOC(char, str, len + 1, gc);
	for (i = 0; i < len; i++) {
		str[i] = rand() % 26 + 'a';
	}
	str[i] = '\0';
	return str;
}
 
char *concat(const char *str_1, const char *str_2) {
	char *str;
	int str_1_len, len;
	int i;
 
	str_1_len = strlen(str_1);
	len = str_1_len + strlen(str_2);
	GC_ALLOC(char, str, len + 1, gc);
	for (i = 0; i < str_1_len; i++) {
		str[i] = str_1[i];
	}
	for (; i < len; i++) {
		str[i] = str_2[i - str_1_len];
	}
	str[i] = '\0';
	return str;
}
 
struct vector rand_vector(unsigned len) {
	struct vector v;
	int i;
 
	GC_ALLOC(int, v.row, len, gc);
	for (i = 0; i < len; i++) {
		v.row[i] = rand() % SHRT_MAX;
	}
	v.len = len;
	return v;
}
 
struct vector add_vector(const struct vector v_1, const struct vector v_2) {
	struct vector v;
	int i;
 
	if (v_1.len != v_2.len) {
		puts("different vector length");
		GC_FREE(gc);
		exit(EXIT_SUCCESS);
	}
	GC_ALLOC(int, v.row, v_1.len, gc);
	for (i = 0; i < v_1.len; i++) {
		v.row[i] = v_1.row[i] + v_2.row[i];
	}
	v.len = v_1.len;
	return v;
}
 
void print_vector(struct vector v) {
	int i;
 
	putchar('[');
	for (i = 0; i < v.len; i++) {
		printf("%d%s", v.row[i], i == v.len - 1 ? "" : ", ");
	}
	putchar(']');
}