c++ - Singleton class and thread safety -

class numberstorage { public:     static numberstorage& instance();     double getnumber();     void setnumber(double d); private:     numberstorage() { number = 0.0; };     double number; };  colorramps& colorramps::instance() {     static colorramps instance;     return instance; } 

i think have read somewhere instance() method implemented way thread safe. correct? guess must lock member variable number in getnumber() , setnumber()? how do (c++11)?

1. c++11 compiler makes thread safe. static variables can created 1 single thread.
2. other questions locks both depend on how threads should work methods. if have multiple threads can 1 same piece of memory - use locks.

simple lock can used std::unique_lock , std::mutex:

void setnumber(double number) {     static std::mutex _setnumberlock;     std::unique_lock _lock(&_setnumberlock);      // code }