fatal error using .close()

[gesangbaer]

Hey there.

I'm having trouble closing a file of all things. I'm using fstream and .close() to do it. I'm only reading part way into the file, hen I save my position via tellg() and try to close the file. Since it was crashing I put the file.close() into a try block. It still hangs in the try block. So I checked the flags before the close() and only the good bit is on.

The error is on line 94. It's a runtime error. The program crashes and vista catches it then tries to "find a solution"

Reading from the file works fine. I can open the file in any text editor without trouble.

I compiled using mingw g++.

Here is the code.

[code=c++]#include <stdlib.h>
#include <iostream>
#include <fstream>

using namespace std;

char* fileName="output.txt";
long last=0;
int hostNum=0,parasiteNum=0;

class Cell
{
public:
float r;
float x;
float y;
float z;
};

Cell* parasites;
Cell* hosts;

int main(int argc, char* argv[])
{
if(argc>1)
{
fileName=argv[1];
}

ifstream fin(fileName,ios::in);

if(!fin.is_open())
{
cout<<"Unable to open file: "<<fileName<<"\n";
return -1;
}

string c;

fin>>c;
hostNum=atoi(c.c_str());
if(hostNum<1){cout<<"invalid information in file, host cells: "<<c<<endl;return 1;}
fin>>c;
parasiteNum=atoi(c.c_str());
if(parasiteNum<1){cout<<"invalid information in file, parasites: "<<c<<endl;return 1;}

hosts=new Cell[hostNum];
parasites=new Cell[parasiteNum];

for(int q=0;q< hostNum+parasiteNum;q++)
{
fin>>c;//index
int i=atoi(c.c_str());
float r,x,y,z;
fin>>c;
r=atof(c.c_str());
fin>>c;
x=atof(c.c_str());
fin>>c;
y=atof(c.c_str());
fin>>c;
z=atof(c.c_str());

if(i<hostNum)//we have a host cell
{
hosts[i].r=r;
hosts[i].x=x;
hosts[i].y=y;
hosts[i].z=z;
}
else//we have a parasite
{
parasites[i-hostNum].r=r;
parasites[i-hostNum].x=x;
parasites[i-hostNum].y=y;
parasites[i-hostNum].z=z;
}
}
last=fin.tellg();

cout<<"closing file\n";

if(fin.rdstate() == ios::failbit)cout<<"Fail bit\n";
if(fin.rdstate() == ios::badbit)cout<<"Bad bit\n";
if(fin.rdstate() == ios::goodbit)cout<<"Good bit\n";
if(fin.rdstate() == ios::eofbit)cout<<"EOF bit\n";

try
{
fin.close();
}
catch(...)
{
cout<<"what?\n";
}

cout<<"read the file!\n";

delete [] hosts;
delete [] parasites;

return 0;
}[/code]

EDIT: updated code as it doesn't affect the error I'm getting. was accessing parasites out of bounds, and forgot to release the memory from hosts and parasites.

[gesangbaer]

Here is the exception vista is giving me, though I don't understand why the try block isn't catching it.

Unhandled exception at 0x774b8915 in a.exe: 0xC0000005: Access violation reading location 0x4aa20ee0.

[helios]

You say the exception occurs on line 94? cout<<"what?\n";

In any case, buffer overflows, which is what you have here, cannot be caught with exception handling. In fact, no kind of memory error can be caught in this manner.

[gesangbaer]

Ah, my bad. Line 90. fin.close();

Closing the file is causing a buffer overflow??? Is that what you are saying? If so could you please explain? I just don't get it.

EDIT

I had it pointed out on another forum that I was accessing the parasites array out of bounds. I've fixed that, but I'm still getting the same error on fin.close();

[mm148881]

Hi,
You should also share the file you are trying to read from. I think if a code bug is there, it might be related to the format of your data. I tried your code on two different architectures (Mac - leopard and an Opteron-CentOS) with g++ and icpc, with the following data file:

2
2
1 0.2 0.3 0.4 0.6
3 0.2 0.3 0.4 0.6
1 1.2 1.3 1.4 1.6
3 1.2 1.3 1.4 1.6

and ... it always get to the end, no problem.
Cheers
Max