使用valgrind和gdb进行stoi和调试

Question

so I am supposed to debug code that does not work and I am having issue on the line [x-1] = std::stoi(t);. I know that I need to have c++ 11 compiler to work, which I do but it still is not working. There's a possibility that something else is wrong, but I am not too sure. Thanks in advance.

#include <iostream>
#include <cstdlib>
#include <string>
using namespace std;

int * p;

/*
 *  * Return the sum of the n values in x starting at index 0.
 *   * Note:  x is a pointer to an array of ints.
 *    * If x is null, then return -1.
 *     * If n is 0 and x is not null, then return 0.
 *      */
int sum(int * x, int n);

int main(int argc, char * argv[]){
  int * x = new int[argc];
  for(int i = 1; i < argc; i++){
        string t (argv[i]);
        x[i - 1] = std::stoi(t);   //it says stoi is not a member of std
  }
//int * p;

  cout << "*x is " << (*x) << endl;
  int y = sum(x, argc);
  cout << "y is " << y << endl;
  int z = sum(p, argc);
  cout << "z is " << z << endl;

  return EXIT_SUCCESS;
}

int sum(int * x, int n){
  int sum;
  for(int i = 0; i < n; i++){
    sum = sum + x[i];
  }
        return sum;
}
~

Answer 1

The code compile fine with G++

g++ -std=c++11 main.cpp -o myApplication

Beside having a compiler which support c++11, did you remember to specify the standard from the compiler flag?

EXTRA:

your code then fails because: 1. you have no checks on NULL condition on sum input pointer. 2. you should also initialize sum to 0 or add a check.

here my small fixes:

#include <iostream>
#include <cstdlib>
#include <string>
using namespace std;

int * p;

/*
 *  * Return the sum of the n values in x starting at index 0.
 *   * Note:  x is a pointer to an array of ints.
 *    * If x is null, then return -1.
 *     * If n is 0 and x is not null, then return 0.
 *      */
int sum(int * x, int n);

int main(int argc, char * argv[]){
  int * x = new int[argc];
  for(int i = 1; i < argc; i++){
        string t (argv[i]);
        x[i - 1] = std::stoi(t);   //it says stoi is not a member of std
  }

  p = NULL;

  cout << "*x is " << (*x) << endl;
  int y = sum(x, argc);
  cout << "y is " << y << endl;
  int z = sum(p, argc);
  cout << "z is " << z << endl;

  return EXIT_SUCCESS;
}

int sum(int * x, int n){
  if(x==NULL) return -1;
  int sum = 0;
  for(int i = 0; i < n; i++){
    sum = sum + x[i];
  }
  return sum;
}