c++ - How to get string data back using pointer? -

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i can not string data using pointer char array. give me explanation doing wrong please.

#include "stdafx.h" #include <conio.h> #include <string>  using namespace std;  string getstring() {     return string("255"); }  int _tmain(int argc, _tchar* argv[]) {     char* str_p = const_cast<char*>(getstring().c_str());     printf("pointer : %s\n", str_p);     string str;     str = str_p[0];     str += str_p[1];     str += str_p[2];     printf("constructed : %s\n", str.c_str());      _getch();     return 0; }

the console output :

pointer : constructed :

there lot wrong line:

char* str_p = const_cast<char*>(getstring().c_str());

getstring() returns temporary string. gets destroyed @ end of line. end dangling pointer internal data deallocated. furthermore, const_cast should ever using if really really need - editing data directly asking trouble.

if want pointer string, right thing is:

string old = getstring();        // make sure doesn't go out of scope const char* str_p = old.c_str(); // while pointer around

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