c++ - Access violation error on inserting data to map variable -

i have declared map variable in header file , trying insert values method in cpp file.

in header (.h) file,

class test { public:     void addname(const std::string& name, const std::string& value); private:     std::map<std::string, std::string> m_names; }; 

in .cpp file,

void test::addname(const std::string& name, const std::string& value) {     m_names.insert(std::pair<std::string, std::string>(name, value)); } 

this method throws error: "0xc0000005: access violation reading location 0x0000000000000150."

but if declare map variable in addname method, no error.

i calling addname method class required parameters.

testptr test = nullptr; test->addname(nodedetails.attribute("name"), nodedetails.attribute("value")); 

what issue?

the test object has instancied before being used :

testptr test; test.addname(...); 

or dynamically allocated (using new)

testptr* test = new testptr(); test->addname(...); // //... //     //and don't forget free memory delete test;  

(in case, first method more "memory safe" ;) )