C- Valgrind确定的内存分配错误

Question

bool load(const char *dictionary)
{
// TODO
//create alphanumeric frequency trie from dictionary stored in temporary location
// open dictioary
FILE *dict = fopen(dictionary, "r");
if (dict == NULL)
{
    return false;
}
//beggining of dictionary trie called 'root'
root = (trie*) malloc( sizeof(trie) );
if (root == NULL)
{
    printf("error allocating memory to root for load");
    return false;
}
//beggining of traversal node called 'current' and "attachment" to read/traverse root node
trie* current = NULL;
int a = (int)'a';
int z = (int)'z';
int cha = 0;
current = root;
//construct trie letter branches from ch (character) of single word-lines in dictionary
for ( char ch = fgetc(dict) ; EOF != ch ; ch = fgetc(dict) )
{
            //set cursor letter to indexable value
            if ( ch == ''' )
            {
                cha = (z + 1) - a;
                //printf("@%d ",cha);
            }
            else
            {
                cha = (ch - a);
                //printf("%d ",cha);
            }
            //create or traverse existing letter branch for next letter ch in word-line
            if( current->children[cha] == NULL && ) //(cha >= 0 && cha <=26) )
            {
                //printf("L");
                current -> children[cha] = (trie*) malloc( sizeof(trie) );
                current = current -> children[cha];
            }
            else //if ( cha >= 0 && cha <=26 )
            {
                current = current -> children[cha];
            }
    //for end of word-line in dictionary label as word and reset cursor node to root of dictionary trie (tree)
    if ( ch == 'n' )
    {
        //printf("n");
        current->is_word = true;
        wordcount++;
        current = root;
        //printf("%d", wordcount);
    }
}

我的程序编译并完全按照我正在处理的问题的规定工作，但是我在下面的if语句开头失败了valgrind测试。Valgrind测试返回"尺寸为8的无效"。我希望我下面提供的代码足以澄清我在侮辱系统内存的位置。

if( (cha >= 0 && cha <=26) && current->children[cha] == NULL )
{
    current -> children[cha] = (trie*) malloc( sizeof(trie) );
    current = current -> children[cha];
}
else if ( cha >= 0 && cha <=26 )
{
    current = current -> children[cha];
}

也下面是我的trie节点的结构：

#define COUNT 27
typedef struct trie
{
    bool is_word;
    struct trie *children[COUNT];
}
trie;
//instantiation structures and variables
trie* root;
int wordcount = 0;
bool loaded;
//freetrie function prototype
void freetrie(trie* step);

这是我免费的trie节点的malloc内存：

void freetrie(trie* root)
{
    for(int i = 0; i < 27; i++)
    {
        if (root -> children[i] != NULL)
        {
            freetrie(root -> children[i]);
        }
    }
    free(root);
    return;
}
bool unload(void)
{
    // TODO
    // free memory allocated by load for dictionary
    trie* current = root;
    freetrie(current);
    return true;
}

Answer 1

行if( current->children[cha] == NULL && (cha >= 0 && cha <=26) )仅在访问数组后执行索引边界检查，应重写它以验证索引是否有效在该位置访问数组之前。摆脱魔术数字也是一个好主意：

#define TRIE_CHILDREN_COUNT 27
typedef struct trie
{
    bool is_word;
    struct trie *children[TRIE_CHILDREN_COUNT];
}
trie;

if((0 <= cha) && (cha < TRIE_CHILDREN_COUNT) && (NULL == current->children[cha]))