Question

我需要一个动态数组，所以我在我的代码中使用了malloc ...但是我不知道如何在之后成功释放内存。在我的代码中的某处，我相信我有一个指针重新分配，导致悬空指针错误（当我做child2 = child1时）。有谁知道如何正确释放我的mallocs？提前谢谢。

我的实际代码如下：

private void Button_Loaded(object sender, RoutedEventArgs e)
{
    Button _button = (Button)sender;
    if (string.IsNullOrEmpty(_button.Content.ToString()))
        _button.IsEnabled = false;
}

在我的一个函数中，我有以下内容，其中pop_size和num_nodes之前分别计算为100和10。

typedef struct Edge//per solution
{
int label;//label
float weight;//energy of each edge
} edge;

// creating the chrom structure
typedef struct Chrom
{
edge **gene;
float fitness_score;
}

另外，在释放内存之前，我是否必须首先检查内存是否已正确分配？

Answer 1

child1 = malloc(num_nodes * sizeof(child1));

这是不正确的。您正在为num_nodes指针分配空间（child1是指向Chrom的指针）。您想为num_nodes Chrom实例分配空间。将其更改为

child1 = malloc(num_nodes * sizeof(*child1));

Answer 2

首先，你为Chrom指针分配空间，而不是为Chrom结构分配空间，所以我很惊讶child1 [x] .gene可以正常运行而不会崩溃但只回答代码中提出的问题，

free(child1);//can i free the memory like this?
free (child2);// will it automatically do all 'arrays'?

child1是一个指针数组，每个指针都指向已分配的内存，当你释放（child1）时它将丢失。我先释放每个指针child1 [x] .gene然后释放child1。对于child2来说也是一样。

这可能接近你想要的：

typedef struct Edge//per solution
{
  int label;//label
  float weight;//energy of each edge
} edge;

// creating the chrom structure
typedef struct Chrom
{
  edge *gene;  // changed from edge**
  float fitness_score;
};

int main(void)
{
  int num_nodes = 3;
  int x;

  struct Chrom* child1;

  // if you want num_nodes Chrom entries

  child1 = malloc(num_nodes * sizeof(struct Chrom));

  // Allocating individual edges (I don't know why you declare edge** gene
  // so I will assume that what you intended was edge* gene

  for(x = 1; x <= num_nodes; x++)
  {
     child1[x].gene = (edge*)malloc(sizeof(struct Edge));
  }


  // deallocate your memory

  for(x = 1; x <= num_nodes; x++)
  {
     free(child1[x].gene);
  }

  // free your array of Chroms

  free(child1);

  return 0;

}

如果你想在每个Chrom中使用edegs的2D数组，那么代码就是这样的;此外，我之前的回答中有一个错误; x应该在for循环中初始化为零而不是1，因为这将导致数组索引超出边界并使用低于 - 而不是低于或等于。（警告：我只是略微测试过）：

typedef struct Edge//per solution
{
  int label;//label
  float weight;//energy of each edge
} edge;

// creating the chrom structure
typedef struct Chrom
{
  edge **gene;  
  float fitness_score;
};

int main(void)
{
  int num_nodes = 3;
  int num_edges_x = 2;
  int num_edges_y = 3;
  int x, j;

  struct Chrom* child1;

  // if you want num_nodes Chrom entries

  child1 = malloc(num_nodes * sizeof(struct Chrom));

  // Allocating 2D array of edges for each Chrom
  // USE zero-based indexing.

  for(x=0; x < num_nodes; x++)
  {
     child1[x].gene = (edge**)malloc(num_edges_x * sizeof(edge*));

     // initialise you array of edges

     for (j=0; j<num_edges_x; j++)
     {
         child1[x].gene[j] = (edge*)malloc(num_edges_y * sizeof(edge));           
     }
  }

  // Use a child1[x].gene[x][y]

  child1[0].gene[0][0].label = 3;
  child1[0].gene[0][0].weight = 7.2F;

  printf("\nlabel: %d - weight: %f", child1[0].gene[0][0].label,   child1[0].gene[0][0].weight);

  child1[1].gene[0][0].label = 1;
  child1[1].gene[0][0].weight = 12.4F;

  printf("\nlabel: %d - weight: %f", child1[1].gene[0][0].label,  child1[1].gene[0][0].weight);

  child1[1].gene[1][0].label = 5;
  child1[1].gene[1][0].weight = 112.6F;

  printf("\nlabel: %d - weight: %f", child1[1].gene[1][0].label,      child1[1].gene[1][0].weight);

  // deallocate your memory
  for(x =0; x < num_nodes; x++)
  {

     for (j=0; j<num_edges_x; j++)
     {
        free(child1[x].gene[j]);
     }

     free(child1[x].gene);
  }

  free(child1);

  return 0;
}

如何在c中正确地释放（）我的mallocs

2 个答案: