要一块、用一块、还一块

（本条路线统一用 gcc -std=c11 -O0 编译）程序自己数着"要了几次、还了几次"：

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

static int got = 0, gave = 0;

int *take(int n) { got++; return malloc(n * sizeof(int)); }
void give(int *p) { gave++; free(p); }

int main(void) {
    int *a = take(4);
    for (int i = 0; i < 4; i++) a[i] = (i + 1) * 10;
    int s = 0;
    for (int i = 0; i < 4; i++) s += a[i];
    give(a);
    printf("%d/%d/%d/%d\n", s, got, gave, got - gave);
    return 0;
}