C++ POST request with cURL + JSON Lib
On this line:
curl_easy_setopt(curl, CURLOPT_POSTFIELDS, json_data.dump().c_str());The string object returned by dump() is temporary and destroyed when curl_easy_setopt() exits, thus leaving CURLOPT_POSTFIELDS with a dangling pointer that may or may not still be pointing to the JSON data in memory by the time libCURL tries to post it.
Per the CURLOPT_POSTFIELDS documentation:
The data pointed to is NOT copied by the library: as a consequence, it must be preserved by the calling application until the associated transfer finishes. This behaviour can be changed (so libcurl does copy the data) by setting the
CURLOPT_COPYPOSTFIELDSoption.
So, you need to either:
change
CURLOPT_POSTFIELDStoCURLOPT_COPYPOSTFIELDS:curl_easy_setopt(curl, CURLOPT_COPYPOSTFIELDS, json_data.dump().c_str());save the result of
json_data.dump()to a local variable that does not go out of scope until aftercurl_easy_perform()exits:std::string json = json_data.dump();curl_easy_setopt(curl, CURLOPT_POSTFIELDS, json.c_str());...