Question

过去2天，我一直在尝试释放程序的内存。由于某些原因，我永远无法完全自由。我有一个循环，它在其中两次malloc：

struct entry
{
  int utf8length;
  char * utf8text;

};

for( int i = 0; i < constant_pool_count; i++ )
{
      ent = malloc(sizeof(struct entry));
      if(ent==NULL)
      {
        fprintf(stderr, "Failed malloc, Exiting the program \n");
        exit(-1);
       }
      ent->utf8length = sizeOfUtf;
      carr = malloc(sizeof(char) * sizeOfUtf + 1);
      if(carr==NULL)
      {
        fprintf(stderr, "Failed malloc, Exiting the program \n");
        exit(-1);
      }
       //More code

}

我应该如何释放它们？

Answer 1

在此片段之后的代码中，您可能具有：

ent->utf8text = carr;

您可以分两步释放每个struct entry：

free(ent->utf8text);
free(ent);

请注意，此代码略有不一致：malloc(sizeof(char) * sizeOfUtf + 1);。大小是正确的，因为sizeof(char)是1，但是为了保持一致，它应该显示为：

malloc(sizeof(char) * (sizeOfUtf + 1));

或

malloc(sizeOfUtf + 1);

Answer 2

第一种情况，它们在循环中被释放：

struct entry
{
  int utf8length;
  char * utf8text;

};

...

for( int i = 0; i < constant_pool_count; i++ )
{
      struct entry * ent;
      char * carr;

      ent = malloc(sizeof(struct entry));
      if(ent==NULL)
      {
        fprintf(stderr, "Failed malloc, Exiting the program \n");
        exit(-1);
       }
      ent->utf8length = sizeOfUtf;
      carr = malloc(sizeof(char) * sizeOfUtf + 1);
      if(carr==NULL)
      {
        fprintf(stderr, "Failed malloc, Exiting the program \n");
        exit(-1);
      }

      ent->utf8text = carr; // I suppose

      //More code

      free(ent->utf8text);
      free(ent);
}

第二种情况，您需要使它们脱离循环然后释放它们

struct entry
{
  int utf8length;
  char * utf8text;

};

...

struct entry * all[constant_pool_count];

for( int i = 0; i < constant_pool_count; i++ )
{
      struct entry * ent;
      char * carr;

      ent = malloc(sizeof(struct entry));
      if(ent==NULL)
      {
        fprintf(stderr, "Failed malloc, Exiting the program \n");
        exit(-1);
       }
      ent->utf8length = sizeOfUtf;
      carr = malloc(sizeof(char) * sizeOfUtf + 1);
      if(carr==NULL)
      {
        fprintf(stderr, "Failed malloc, Exiting the program \n");
        exit(-1);
      }

      ent->utf8text = carr; // I suppose
      all[i] = ent;

      //More code
}

... some code

// free them

for( int i = 0; i < constant_pool_count; i++ )
{
   free (all[i]->utf8text);
   free (all[i]);
   // may be "all[i] = NULL;" if useful ?
}

无法释放C语言中的内存-动态结构和数组

2 个答案: