Question

Adding a string in a CURL post variables

curl_formadd(&formpost,
               &lastptr,
               CURLFORM_COPYNAME, "submit",
               CURLFORM_COPYCONTENTS, "send",
               CURLFORM_END);

This up there works just fine the POST key comes with “submit” in the page content.

but this:

string post = "submit";
 curl_formadd(&formpost,
               &lastptr,
               CURLFORM_COPYNAME, &post,
               CURLFORM_COPYCONTENTS, "send",
               CURLFORM_END);

but this up here the page content in result comes with a extra weird character like “◘ER☺submit” instead of clean “submit”

what am I missing here? thanks!

Answer 1

You should use std::string::c_str():

string post = "submit";
curl_formadd(&formpost,
             &lastptr,
             CURLFORM_COPYNAME, post.c_str(),
             CURLFORM_COPYCONTENTS, "send",
             CURLFORM_END);

By using &post, you are extracting the address of the std::string, which is a completely different data type than a const char* you used when simply using the quoted string. std::string::c_str, on the other hand, returns the const char * that actually stores the string.

EDIT: regarding your concatenation question, std::string can be concatenated. Therefore:

std::string data = "submit";
data += " foo"; //data will be "submit foo";
std::string data2 = data + " yey"; //data2 will be "submit foo yey";