Unreleased

These changes are part of the develop branch, but not of a release yet.

Converting an rvalue container to JSON (json j = std::move(vec);, json j = std::map<std::string, std::string>{...};) now moves the elements instead of copying them (e.g., std::vector<std::string> with 100,000 strings: 4.7 ms to 2.3 ms). Two consequences: the source container is left in a valid but unspecified (moved-from) state, and if an exception is thrown during the conversion, the source may be partially moved-from, so the strong exception guarantee no longer holds for the source of an rvalue conversion (the JSON value itself is unaffected). Lvalues and const objects are still copied. See basic_json.

API changes