Stack Corrupted

catherineod

Hi, could anyone help me with this problem? I'm getting the following error message when I try to run this code -
"Run-Time Check Failure #2 - Stack around the variable 'vY' was corrupted"
Where am I going wrong? (I'm using visual C++)

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#include <iostream>        // Needed for cin, cout, cerr, endl

#include <cmath>        // Needed for Sin/Cos functions
 
using std::cout;

using std::endl;
 
#include <iomanip>
 
using std::setw;
 
int main()

{

//Will need arrays to store particles inital x and y co-ordinates so declaring them
 
const int numParticles = 10;
 
double pX[numParticles];

double pY[numParticles];
 
// And arrays for particles velocity in x and y directions
 
double vX[numParticles];

double vY[numParticles];
 
int screenWidth = 100;

int screenHeight = 100;
 
double dRand(double max);
 
// Initialise particle positions and velocities randomly.

void initParticles();

{

//intialise particle position co-ordinates and velocities

    int numParticles = 10; //need to set the number of particles in the array to something!

    {

        for(int i=0; i<numParticles; i++) //counting through each element of the array

            pX[i] = dRand(screenWidth);   //particle's inital x co-ordinate

               pY[i] = dRand(screenHeight);  //particle's inital y co-ordinate

            vX[i] = dRand(100);           //initial x velocity

            vY[i] = dRand(100);           //inital y velocity

    }

}

for (int j=0; j<10; j++)

cout<< setw ( 7 ) << j << setw ( 13 ) << pX[j] << endl;
 
return 0;

}

double dRand(double max)

{

return max * (static_cast<double>(rand()) /static_cast<double>(RAND_MAX));

}

Thanks

Banfa

In this section

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for(int i=0; i<numParticles; i++) //counting through each element of the array

    pX[i] = dRand(screenWidth);   //particle's inital x co-ordinate

    pY[i] = dRand(screenHeight);  //particle's inital y co-ordinate

    vX[i] = dRand(100);           //initial x velocity

    vY[i] = dRand(100);           //inital y velocity

You are missing { and } round the statements to execute in the for loop. The loop is equivilent to

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for(int i=0; i<numParticles; i++) //counting through each element of the array

{

    pX[i] = dRand(screenWidth);   //particle's inital x co-ordinate

}
 
pY[i] = dRand(screenHeight);  //particle's inital y co-ordinate

vX[i] = dRand(100);           //initial x velocity

vY[i] = dRand(100);           //inital y velocity

When pY, vX and vY are accessed i = numParticles+1 making all of these out of bounds array accesses.

Correct use of { and } will solve the problem

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for(int i=0; i<numParticles; i++) //counting through each element of the array

{

    pX[i] = dRand(screenWidth);   //particle's inital x co-ordinate

    pY[i] = dRand(screenHeight);  //particle's inital y co-ordinate

    vX[i] = dRand(100);           //initial x velocity

    vY[i] = dRand(100);           //inital y velocity

}

catherineod

Thanks, should've noticed that!
Have now got another problem however, when I build and run the code it flashes up the program very quicky (too quickly to even be read really) and then it disappears! Do you know what's going on?

Ganon11

When you finish your int main() function, you can include the statement

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system("PAUSE");

right before your return statement to pause the screen before quitting. This should allow you to see any output generated before the program closes.

If this doesn't help, there may be another error inside your code causing the program to terminate early.

Banfa

Quote:

Originally Posted by Ganon11

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system("PAUSE");

Personally I really hate this approach but can't think of a really good argument against it (it is a little non-portable though) although you can end up having to press space twice in some instances. Partly because it is not a part of the programs functionality.

I suspect the reason it flashes up is that you are running in debug mode. In most IDEs if you run in debug mode then the program will not pause once it has finished because it assumes you will set a break point if you want the program to stop (I assume). If instead of running it in the debugger you just run it (as normal) then in most environments the OS will pause before shutting the window (or at least it is configurable).

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