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#1 by (3 votes)

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Good night, I wrote a file in c ++ but it is no longer working, the code compiles everything right, but if I put it to run it appears the message that the program stopped working, if anyone can help me I will be very grateful. code below!

#include <stdio.h>
#include <math.h>
#include <iostream>
#include <fstream>
#include <vector>
#include <stdlib.h>
#include <string>

#define K 9.0e09  // constante eletrica no vacuo

using namespace std;

int main(int argc,char **argv)
{

   int Q1 = atof(argv[1]);
   int Q2 = atof(argv[2]);
   double dist = atof(argv[3]); 
/*

   int Q1, Q2;
   double dist;

   cin >> Q1;
   cin >> Q2;
   cin >> dist;


  //char *OutputFileName=argv[4];
   int Q1 = 1;
   int Q2 = 2;
   double dist = 0.01;
*/

   ofstream Output1("Output.dat");  // valor da força elétrica (em Newtons)

   cout << "Forca eletrica = " << (K*Q1*Q2*pow(10,-12))/pow(dist,2) << endl;

   Output1 << Q1 << " " << Q2 << " " << dist << " " << (K*Q1*Q2*pow(10,-12))/pow(dist,2) << endl;

   return 0;

} //int main
/*-----------------------end of main program--------------------------*/

c++

asked by anonymous 21.12.2018 / 02:39

1 answer

Select and display character in more than one div Convert value to number returns NaN

score 3 · Answer 1

Igor ,

@ jefferson-quesado commented on checking argc to prevent 'strange errors' when running the program. It is critical that you do such a check if you expect some argument in the program call. In your case, you will have 4 arguments: the program name itself, Q1 , Q2 and dist .

If you invoke / execute the program without providing the arguments, it executes main() . Within main() , it executes the Q1 assignment but then stops executing because argv will attempt to access a non-reserved memory area when Q2 is attempting to store the argv value. The segmentation fault error appears.

If you invoke / execute the program by giving arguments partially, it executes main() . Within main() , it stops execution because argv will try to access a non-reserved memory area, and although at least Q1 passes the test, Q2 or dist will try to store the value nonexistent. The segmentation fault error appears.

In this case, if you had checked argc , you would probably have noticed that forgot your arguments when invoking the program . Your code is OK , running normally. The only way for it to provide a segmentation fault (or segmentation fault ) is actually not providing the necessary arguments when running your compiled.

Error examples:

g++ codigo.cpp -o meu_programa
./meu_programa  # sem argumentos
Segmentation fault (core dumped)

g++ codigo.cpp -o meu_programa
./meu_programa 20 # argumentos parciais
Segmentation fault (core dumped)

Correct example:

g++ codigo.cpp -o meu_programa
./meu_programa 10 20 30 # todos os argumentos
> Forca eletrica = 0.002

You can use OnlineGDB to verify that it works normally

Note that I have exemplified how I would be in Linux where I use g ++ to compile. In Windows you may be using some IDE or something. But the central idea is the same: you need the arguments!