c - malloc() 用于字符串数组，但没有像希望的那样工作

Question

我正在尝试创建一个函数，它接受一个字符串和一个指向字符串数组的指针以及malloc() char数组的数组，并复制字符串的每个单独的单词。这就是我到目前为止所拥有的，我想我已经接近了，我只是在努力在数组数组上使用 malloc() 。

int string_parser(char *inp, char **array_of_words_p[])
{
    int CurrentChar = 0;                //Variable Initialization
    char *buffer;                       //Variable Initialization

    /* Allocate memory and check for errors allocating memory */
    //Allocate memory to buffer the size of the input string
    buffer = (char*)malloc(strlen(inp));    
    if (buffer == NULL)
    {
        printf("Error allocating memory..\n");
        return -1;
    }

    /* Move input string into buffer before processing */
    for (CurrentChar = 0; CurrentChar < strlen(inp) + 1; CurrentChar++)
    {   //For every character in input
        if (inp != NULL)                                                    
        {
            //Move input character into buffer
            buffer[CurrentChar] = inp[CurrentChar];     
        }
    }

    /* Convert string into array of words */
    char ** stringbuffer = NULL;        

    //Convert string to array of words
    char *  CurrentWord = strtok_s(buffer, " ", *array_of_words_p);     

    //Variable Initialization
    int numspaces = 0;

    while (CurrentWord)                                                 
    {
        //Allocate memory for size of string
        stringbuffer = (char**)realloc(stringbuffer, sizeof(char**) * ++numspaces); 
        if (stringbuffer == NULL)                                       
        {
            return -1;
        }
        stringbuffer[numspaces - 1] = CurrentWord;

        //Reset Current word to null        
        CurrentWord = strtok_s(NULL, " ", *array_of_words_p);       
    }

    //Reallocate memory to include terminating character
    stringbuffer = (char**)realloc(stringbuffer, sizeof(char**) * (numspaces + 1)); 
    stringbuffer[numspaces] = 0;                                        

    /* Write processed data into returned argument */
    *array_of_words_p = (char**)malloc(sizeof(char**) * (numspaces + 2));           
    memcpy(*array_of_words_p, stringbuffer, (sizeof(char*) * (numspaces + 2))); 

    free(stringbuffer);                                             
    return numspaces;                                                   
}

Answer 1

    //Allocate memory to buffer the size of the input string
    buffer = (char*)malloc(strlen(inp));    

输入字符串的大小包括终止\0 ，所以你需要:

    buffer = malloc(strlen(inp)+1);

    //Convert string to array of words
    char *  CurrentWord = strtok_s(buffer, " ", *array_of_words_p);     

滥用 *array_of_words_p 是不明智的对于上下文保存变量，因为这需要对其进行适当的初始化。更好:

    char *context, *CurrentWord = strtok_s(buffer, " ", &context);
    …
        CurrentWord = strtok_s(NULL, " ", &context);

        //Allocate memory for size of string
        stringbuffer = (char**)realloc(stringbuffer, sizeof(char**) * ++numspaces); 

这可能不会造成伤害(由于指针大小相同)，但是 sizeof(char**)严格来说是错误的，因为字符串数组的元素类型为 char * 。正确:

        stringbuffer = realloc(stringbuffer, sizeof (char *) * ++numspaces);
    …
    stringbuffer = realloc(stringbuffer, sizeof (char *) * (numspaces + 1));

    /* Write processed data into returned argument */
    *array_of_words_p = (char**)malloc(sizeof(char**) * (numspaces + 2));           
    memcpy(*array_of_words_p, stringbuffer, (sizeof(char*) * (numspaces + 2))); 

    free(stringbuffer);                                             

您可以避免这种不必要的复制，并避免访问未分配的内存 stringbuffer[numspaces+1]将上面的内容替换为:

    *array_of_words_p = stringbuffer;

除此之外，您的函数可以正常工作并且可以像这样调用:

    char **array_of_words;
    int n = string_parser("this here is an example string", &array_of_words);
    for (int i = 0; i < n; ++i) puts(array_of_words[i]);