c - 如何返回指向结构数组内元素的指针？

Question

我在这里做错了什么？

/*
 * Consider the following pseudo code !
 */
typedef struct foobar {
    unsigned char id, count;
    struct foobar *child;
} foobar;

foobar root = (foobar *) malloc( sizeof(struct foobar) );
root->child = (foobar *) malloc( sizeof(struct foobar) );

root->count++;
root->child[0].id = 1;

root->count++;
root->child[1].id = 2;

root->count++;
root->child[3].id = 3;

root->child[0].child = (foobar *) malloc( sizeof(struct foobar) );

root->child[0].child[0].count++;
root->child[0].child[0].id = 4;

root->child[1].child = (foobar *) malloc( sizeof(struct foobar) );
root->child[0].child[0].count++;
root->child[1].child[0].id = 5;

root->child[0].child[0].count++;
root->child[1].child[1].id = 6;

/* and so on */

/*
 * Function to search for an ID inside the tree,
 * it should call itself in order to go deeper into
 * the childs, but taht's not implemented here
 */
foobar *search( unsigned char id, foobar *start_node = NULL );
foobar *search( unsigned char id, foobar *start_node ) {
    if( start_node == NULL ) {
        unsigned char x;
        for( x = 0; x < root->count; x++ ) {
            if( root->child[ x ].id == id ) {
                foobar *ptr = &root->child[ x ];
                /* If I call ptr->id now, it will return the correct value */
                return &ptr;
            }
        }

    } else { /* not implemented */ }
}

/* Search the array for and ID */
foobar **ptr = this->search( 1 );
/* If I call ptr->id now, it will return memory garbage */

Answer 1

root 有 4 个 child (因为你访问 root->child[3])，所以你必须分配足够的内存:

root->child = (foobar *) malloc( sizeof(struct foobar) * 4 ); //at least 4

此外，您应该返回 foobar 指针本身，而不是指向它的指针(即 return ptr; 而不是 return &ptr;。