CODEWITHSUNDEEP
c++stringbuffer-overflow
Captain Lightning
Captain Lightning

Reputation: 10773

String overflow in C++? This inecessant beeping is weird

I'm startin development on a junk file generator, but for some reason if I use a large number it will beep infinitely until the file is finished, I'm thinking there is a \a character somewhere in the ascii table, or it's overflowing and causes an error beep. Anyone wanna explain why this thing is screaming at me?

#include <string>
#include <iostream>
#include <cstdio>
#include <cstdlib>
#include <fstream>
#include <time.h>
#include <windows.h>
#define print cout<<

using namespace std;

int numberof,i;
char charvalue;
string charlist,filename;

int main()
{
    srand (time(NULL));
    print "What do you want the name of your file to be?(with a .txt extension)\n";
    getline(cin,filename);
    print "\nHow many characters do you want?\n";
    cin>>numberof;

    for(numberof>0;numberof!=0;numberof--)
        {
        i = rand() % 255 + 32;
        charvalue=i;
        charlist=charlist+charvalue;
        print charlist;
        }

    ofstream writefile(filename.c_str());
    writefile<<charlist;
    writefile.close();
    ShellExecute(NULL, "open", filename.c_str(), NULL, NULL, SW_SHOWNORMAL);
    return 0;
}

Seems like at this point the characters are coming out alright in the end, but it only writes 1/4 of them to the text file. Anyone know why?

Upvotes: 0

Views: 369

Answers (5)

fredoverflow
fredoverflow

Reputation: 263360

I'm thinking there is a \a character somewhere in the ascii table

Yes, it is in position 7, I believe.

Also, this:

for(numberof>0;numberof!=0;numberof--)

should be this:

 for(; numberof > 0; numberof--)

The condition goes in the middle, and you do not need any initialization, hence the empty statement at the beginning of the for-loop.

Also, the printable ASCII characters only range from 32 to 126, so you should write:

i = rand() % 95 + 32;

Also, the following is extremely inefficient, as it generates a new string object every time:

charlist=charlist+charvalue

Do this instead:

charlist.push_back(charvalue);

Upvotes: 2

david
david

Reputation: 18288

Remove the print charlist so you're not printing the bell characters out.

Upvotes: 0

Brent Writes Code
Brent Writes Code

Reputation: 19623

The fact that you're printing the entire charlist every time means as fast as you can means that as soon as you generate at least a couple \a characters in the output string (the odds of which aren't too bad), you will get nothing but incessant beeping.

Upvotes: 1

Jerry Coffin
Jerry Coffin

Reputation: 490728

i = rand() % 255 + 32;

You probably want this to be something like:

i = rand() % (255-32) + 32;

You also really want to get rid of this:

#define print cout<<

As it stands, when (not if) whoever is grading your homework decides to kill you, he (she?) will almost certainly be found not guilty of murder on the grounds that it was self defense.

Upvotes: 7

cababunga
cababunga

Reputation: 3114

You meant to say

i = rand() % 223 + 32;

Upvotes: 2

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