memory leak or some other problem in C++ and vector of strings

i keep getting memory leaks everytime I run this function in a loop:

uint32_t *padMessages(uint32_t *messages, const std::vector<std::string> &words) 
{
    uint32_t output[16];
    uint32_t size = words.size();
    uint32_t i, x, y;

    messages = (uint32_t *)malloc(16 * size * sizeof(uint32_t));

    x = 0;
    for(i = 0; i < size; i++) {
        padMessage((uint32_t *)_strdup(words[i].c_str()), output, strlen((const char *)words[i].c_str()) * 8);
        for(y = 0; y < 16; y++) {
            messages[x] = output[y];
            x++;
        }
    }

    return messages;
}

the code calling this function is

do {
    for(i=0 ; i<len ; i++) 
        temp[i] = letters[entry[i]];
    temp[len] = '\0';

    // store generated word to words vector
    words[array_count] = temp;

    // increment vector counter and total word count
    array_count++;
    word_count++;

    if(array_count == 100000) {
        // reinitialize array_count
        array_count = 0;

        // pad messages
        messages = padMessages(messages, words);

        free(messages);
        free(result);

        std::vector<std::string>().swap(words);
        words.resize(100000);
    }
    for(i=0 ; i<len && ++entry[i] == nbletters; 开发者_如何转开发i++) entry[i] = 0;
} while(i<len);

where is my memory leaking?

This:

(uint32_t *)_strdup(words[i].c_str())

...allocates memory dynamically, and I don't see any matching call to free for the memory allocated.

I'd use std::string throughout.

You are calling strdup in the loop in the top function and you are never free'ing those strings you are allocating.

My guess would be that the memory allocated by _strdup isn't freed.