c++libcurl

Why does passing address of std::string to libcurl work?

Almost every C++ libcurl example goes like this:

std::string response_string;
curl_easy_setopt(curl, CURLOPT_URL, "http://some url");
curl_easy_setopt(curl, CURLOPT_WRITEFUNCTION, getAnswerFunction);
curl_easy_setopt(curl, CURLOPT_WRITEDATA, &response_string);

Question is why does &response_string work where a C char* is expected?

Also, why does response_string.c_str() core dump if I use that instead of &response_string?

PS The above snippet is taken from this question but most examples use the same method

Solution

  • Question is why does &response_string work where a C char* is expected?

    A C char* is not necessarily expected. Whatever you pass is later given as an argument to the WRITEFUNCTION . It could be char*, FILE* , std::string*, or any other pointer type depending on how WRITEFUNCTION is implemented.

    Also, why does response_string.c_str() core dump if I use that instead of &response_string?

    Probably due to passing a char* where a std::string* is expected.