simple_gc.c

#include <stdio.h>
#include <stdlib.h>
#include <stdint.h>

void* mallocAddress = NULL;

int
look_for_pointer(void* start, void* end, void* address, void* ignore) {
	if(address == NULL) return 0;

	int count = 0;
	void* i;

	for(i = start; i != end; i+=8) {
		if( (intptr_t)(*(void**)i) == (intptr_t)(address) &&
				(intptr_t)(i) != (uintptr_t)(ignore)
			) {
			count++;
		}
	}

	return count;
}

void*
gc_malloc(int size) {
	mallocAddress = malloc(size);
	return mallocAddress;
}

void
GC() {
	int pointerCount = 0;
	FILE* fp;
	char* line = NULL;
	size_t len = 0;
	ssize_t read;

	fp = fopen("/proc/self/maps", "r");
	if (fp == NULL)
	 exit(EXIT_FAILURE);

	while ((read = getline(&line, &len, fp)) != -1) {
		long start, stop;
		char read, write;
		sscanf(line, "%16lx-%16lx %c%c", &start, &stop, &read, &write);
		if (read == 'r' && write == 'w') {
			pointerCount += look_for_pointer((void*)start, (void*)stop, mallocAddress, &mallocAddress);
		}
	}

	if (line)
		free(line);

	fclose(fp);

	if (pointerCount == 1) {
		printf("Freeing %p.\n", mallocAddress);
		free(mallocAddress);
		mallocAddress = NULL;
	}
}

int
main(void) {
	gc_malloc(10);
	GC();
	exit(EXIT_SUCCESS);
}