Valcurnd中仍然可以获得libcurl C ++代码的泄漏摘要

Question

The following functions in libcurl saves a file and returns the http status code. However, when I run this using valgrind, it is reporting 0 bytes for "definitely lost", "indirectly lost", "possibly lost", but it is reporting 47448 bytes for "still reachable" . I'm trying to resolve the "still reachable" bytes.

Are there any potential memory leaks in the code below?

size_t write_data(void *ptr, size_t size, size_t nmemb, FILE *stream){
    size_t written = fwrite(ptr, size, nmemb, stream);
    return written;
}

void connectAndSaveFile(char* url, char* output_file_name){
    CURL *curl;

    curl = curl_easy_init();
    if (curl)    {
        FILE *fp = fopen(output_file_name,"wb");
        curl_easy_setopt(curl, CURLOPT_URL, url);
        curl_easy_setopt(curl, CURLOPT_WRITEFUNCTION, write_data);
        curl_easy_setopt(curl, CURLOPT_WRITEDATA, fp);
        curl_easy_perform(curl);
        curl_easy_cleanup(curl);
        fclose(fp);
    }
}

string get_http_status_code(string URL) {
    CURL *session;
    session = curl_easy_init();
    curl_easy_setopt(session, CURLOPT_URL, URL.c_str());
    curl_easy_setopt(session, CURLOPT_NOBODY, true);

    CURLcode curl_code = curl_easy_perform (session);
    long http_code = 0;
    curl_easy_getinfo (session, CURLINFO_RESPONSE_CODE, &http_code);

    curl_easy_cleanup(session);

    std::ostringstream buff;
    buff << http_code;
    return buff.str();
}

Answer 1

1. "still reachable" is most frequently not actually a leak

2. you might get slightly less memory reachable if you use curl_global_init and curl_global_cleanup

Answer 2

The most of the code mention above uses libcurl . So I think we would have to look the documentation and read about API and what are the recommended steps.

However in the below method, client is passing pointer in which fwrite API is writing and returns back to the caller. This memory needs to be released in client(who would be calling this function) code once usage is complete.

size_t write_data(void *ptr, size_t size, size_t nmemb, FILE *stream)

However in pure C++ ways, we should use std::fstream & std::string so that we need not worry about the memory management. For more informtion you may refer to following link:

https://stackoverflow.com/a/22048298/2724703