[Python] How to pass string to REST API using libcurl in cpp

I want to send string to my rest API call in c++. So, I am using libcurl library.

CURL *curl;
CURLcode res;

curl = curl_easy_init();
if(curl) {
curl_easy_setopt(curl, CURLOPT_URL, "localhost:5000/sample");
curl_easy_setopt(curl, CURLOPT_POSTFIELDS, "{\"hi\" : \"there\"}");
res = curl_easy_perform(curl);
curl_easy_cleanup(curl);

std::cout << res << std::endl;
}


O/P from flask API is,

ImmutableMultiDict([('{"hi" : "there"}', '')])
​

the above code is working:

I am getting the sent result in my python Flask application.

but,

string body = "{\"hi\" : \"there\"}";
CURL *curl;
CURLcode res;

curl = curl_easy_init();
if(curl) {
curl_easy_setopt(curl, CURLOPT_URL, "localhost:5000/sample");
curl_easy_setopt(curl, CURLOPT_POSTFIELDS, body);
res = curl_easy_perform(curl);
curl_easy_cleanup(curl);

std::cout << res << std::endl;
}


O/P from flask API is:

ImmutableMultiDict([('��-ؿ\x7f', '')])
​

this code is not working. the only difference is i am assigning the string to a variable and passing that to curl.

I am wondering why it's working? how to pass variable to curl?

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