Call a destructor function when variable is out of scope.

unique-ptr.c

#include <stdio.h>
#include <stdlib.h>
#define unique_ptr(destructor) __attribute__ ((cleanup(destructor)))

void destructor(void *ptr) {
	void *aux = *(void**)ptr;
	
	fclose(aux);
	
	printf("file closed.\n");
}

/*///////////////////////////////////
	
		Testing:
		
///////////////////////////////////*/

int main(void) {
	{
		unique_ptr(destructor) FILE *fp;
	
		fp = fopen("test-file.txt", "w");
		fputs("Hello, world!\n", fp);
	}
	//destructor is called here
	
	system("pause");
	
	return 0;
}