Malloc 中断函数

Question

我有一个问题，我的 malloc 破坏了我的程序。删除它会使它工作，但我需要它进一步。有人可以解释我做错了什么吗？提前致谢！！

我的 graph.c

中有这个功能

bool graph_initialise(graph_t *graph, unsigned vertex_count)
    {
      assert(graph != NULL);
        graph = (struct graph_s*) malloc(sizeof(struct graph_s));
        if (graph == NULL){return true;}
        graph->vertex_count = vertex_count;

        graph->adjacency_lists = (struct adjacency_list_s*) malloc(vertex_count * sizeof(struct adjacency_list_s));
        if (graph->adjacency_lists == NULL){
        return true;
        }

        int i;
        for (i = 1; i < vertex_count; ++i){
        graph->adjacency_lists[i].first = NULL;
        }
      return false;

这在我的 graph.h

typedef struct edge_s
{
  /* Points to the next edge when this edge is part of a linked list. */
  struct edge_s *next;

  unsigned tail;    /* The tail of this edge. */
  unsigned head;    /* The head of this edge. */
  unsigned weight;  /* The weight of this edge. */
} edge_t;

typedef struct adjacency_list_s
{
  edge_t *first; /* Pointer to the first element of the adjacency list */
} adjacency_list_t;

/* Type representing a graph */
typedef struct graph_s
{
  unsigned vertex_count; /* Number of vertices in this graph. */
  unsigned edge_count;   /* Number of edges in this graph. */

  /* Pointer to the first element of an array of adjacency lists. The array
   * is indexed by vertex number
   */
  adjacency_list_t *adjacency_lists;
} graph_t;

Answer 1

我怀疑这个问题是因为您希望此函数为您分配 grph，然后从调用代码对分配的图进行操作（您没有显示调用代码）

即你正在做类似

的事情

graph *gptr;
graph_initialise(gptr,42);
printf("vc = %d", gptr->vertex_count);

问题是 grpah_initialize 没有设置 gptr。你需要

bool graph_initialise(graph_t **gptr, unsigned vertex_count)
    {
        *gptr = (struct graph_s*) malloc(sizeof(struct graph_s));
        graph_t *graph = *gptr;
        if (graph == NULL){return true;}
        graph->vertex_count = vertex_count;

        graph->adjacency_lists = (struct adjacency_list_s*) malloc(vertex_count * sizeof(struct adjacency_list_s));
        if (graph->adjacency_lists == NULL){
        return true;
        }

        int i;
        for (i = 1; i < vertex_count; ++i){
        graph->adjacency_lists[i].first = NULL;
        }
      return false;

然后这样称呼它

graph *gptr;
graph_initialise(&gptr,42);
printf("vc = %d", gptr->vertex_count);

另外，for 循环应该从 0 而不是 1 开始

Malloc 中断函数

Malloc breaks function

c

malloc

initialization

graph