c - 此 C 代码中是否存在内存泄漏？

Question

在

https://en.wikibooks.org/wiki/Algorithm_Implementation/Mathematics/Extended_Euclidean_algorithm

C 实现在递归函数内调用 malloc。这不是内存泄漏吗？

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

int mod (int a, int b){
    return a %b; 
}   

int *extendedEuclid (int a, int b){
   int *dxy = (int *)malloc(sizeof(int) *3);

   if (b ==0){
      dxy[0] =a; dxy[1] =1; dxy[2] =0;

       return dxy;
   }
   else{
       int t, t2;
       dxy = extendedEuclid(b, mod(a, b));
       t =dxy[1];
       t2 =dxy[2];
       dxy[1] =dxy[2];
       dxy[2] = t - a/b *t2;

       return dxy;
    }
}

int main(void)
{
   int a =99, b =78;
   int *ptr;

   ptr =extendedEuclid (a, b);
   printf("%d = %d * %d + %d * %d \n",ptr[0], a, ptr[1], b, ptr[2] );

   return 0;        
}

如何释放在递归函数中分配的内存？

Answer 1

Isn't that a memory leak?

是的，是的。每次进行递归调用时，即这里:

dxy = extendedEuclid(b, mod(a, b));

当 dxy 被新值(又名返回值)覆盖时，刚刚 malloc 的内存泄漏

代码应该更像:

int *extendedEuclid (int a, int b){
    int *dxy;
    if (b ==0){
        dxy = (int *)malloc(sizeof(int) *3);  // Move malloc to here
        dxy[0] =a; dxy[1] =1; dxy[2] =0;

        return dxy;
    }
    else { ....

因此malloc只执行一次，即没有递归调用时