c++ - Unintialized local variable 'e' used -


i have code. should work perfectly. it's circle calculator; i'm doing exercise. want user have option return the 'main menu.' made yes/no prompt using char* e; it's uninitialized. how can initialize 

#include <iostream>  using namespace std;  class circlecalc { public:     double const pi = 3.1415962543;     double diameter;     double radius;     double circumference;  };  int _welcome() {     circlecalc calc;     cout << endl;     int = 0;     char* e;     cin >> i;     while (i != 5)     {         switch (i) {         case(1) :             cout << "enter radius." << endl;             cin >> calc.radius;             cout << endl;             cout << (calc.radius * 2) * calc.pi << endl;             cout << "exit? [y/n]" << endl;             cin >> e;             if (e == "y") {                 _welcome();             }              else if (e == "n") {             }              else {                 cerr << "unsupported function" << endl;             }          case(2) :             cout << "enter diameter" << endl;             cin >> calc.diameter;             cout << endl;             cout << (calc.diameter * 2) * calc.pi << endl;             cout << "exit? [y/n]" << endl;             cin >> e;             if (e == "y") {                 _welcome();             }              else if (e == "n") {             }              else {                 cerr << "unsupported function" << endl;             }             break;          case(3) :             cout << "enter circumference" << endl;             cin >> calc.circumference;             cout << endl;             cout << (calc.circumference / 2) / calc.pi;             cout << "exit? [y/n]" << endl;             cin >> e;             if (e == "y") {                 _welcome();             }              else if (e == "n") {             }              else {                 cerr << "unsupported function" << endl;             }             break;          case(4) :             cout << "enter circumference" << endl;             cin >> calc.circumference;             cout << endl;             cout << calc.circumference / calc.pi;             cout << "exit? [y/n]" << endl;             cin >> e;             if (e == "y") {                 _welcome();             }              else if (e == "n") {             }              else {                 cerr << "unsupported function" << endl;             }             break;          case(5) :             return(0);             break;          default:             cerr << "unsupported function." << endl;         }     } }

instead of:

char* e;

use:

std::string e;

the reason get:

unintialized local variable 'e' used

is e not set when passed operator>> used cin, initialize assign array it, ie:

char arr[128] = {0}; char* e = arr;

operator>> cin stream expect have provided memory buffer read string located, char* e; not bound such buffer, , end in (possibly) crash (undefined behaviour).


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