CODEWITHSUNDEEP
c++segmentation-fault
Gekkey Mathews
Gekkey Mathews

Reputation: 1

I have segfaults!

Today is my first time using c++ in a while. I am normally a python programmer. I keep getting segfaults and I've isolated it to the commented lines. (the ones that are commented cause segfaults when uncommented.)

#include <iostream>
#include <fstream>
#include <string>
using namespace std;
#include "defaultfile.h"

int main()
{
    ifstream mapin;
    string map;
    string s;
    int i = 0;
    while (i<=22){i++;top[i][0]="__";i++;};i=0;
    while (i<=21){i++;frw[i][0]="/";i++;};i=0;
    while (i<=21){i++;bck[i][0]="\\";i++;};i=0;
    //while (i<=45){i++;spc[i][0]=" ";i++;};i=0;
    //while (i<=112){i++;spc[i][1]="n";i++;};i=0;
    while (i<=22){i++;cout<<top[i][1]<<endl;i++;};i=0;
    while (i<=21){i++;cout<<frw[i][1]<<endl;i++;};i=0;
    while (i<=21){i++;cout<<bck[i][1]<<endl;i++;};i=0;
    //while (i<=45){i++;cout<<spc[i][1]<<endl;i++;};i=0;
    ...
}

the header is:

string top[23][3] = 
{{"", "", ""},
...
{"", "", ""}};
string frw[22][3] = 
{{"", "", ""},
...
{"", "", ""}};
string bck[22][3] = 
{{"", "", ""},
...
{"", "", ""}};
string spc[46][3] = 
{{"", "", ""},
...
{"", "", ""}};

Edit: Thank you. It's always the stupid things that I miss and spend an hour trying to find. All I needed was someone else to point it out.

Upvotes: 0

Views: 261

Answers (4)

ChrisWue
ChrisWue

Reputation: 19020

Arrays are 0 based. You are writing over the end on each one of them. It crashed on spc because it's the last one. On the other ones you write into the memory of the following one.

To clarify: You do while (i <= 45) { i++; spc[i] ... Now if i is 45 then you increment it to 46 and you access spc[46] which is outside of the bounds. Same for all the other lines.

Furthermore you only initialize every second field - not sure if that is intentional.

Upvotes: 1

Brian Roach
Brian Roach

Reputation: 76898

while (i<=112){i++;spc[i][1]="n";i++;};i=0;

You defined spc as:

string spc[46][3]

Upvotes: 2

Ben Voigt
Ben Voigt

Reputation: 283634

You're indexing spc all the way up to 112, but only 0-45 are valid for the first index.

Upvotes: 1

corsiKa
corsiKa

Reputation: 82579

//while (i<=112){i++;spc[i][1]="n";i++;};i=0;

This will segfault on spc[46] for sure.

Upvotes: 0

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