To store the Qtablewidget data to .csv or xl file - Issue

[patilakash]

The following is my piece of code:

QString fileName = appData + DIR+ "AISTABLE";
fileName = fileName + d_local.toString("_yyyy-MM-dd") + t_local.toString("_HH-mm-ss") + ".csv";
f_out = fopen(fileName.toAscii().data(), "wb+");
if (f_out == NULL) {
    return;
}
 
QString headerString = "d1,d2,d3,d4,d5,d6,d7,d8,d9,d10,d11\r\n";
 
for(int row = 0;row <ui->tableWidget->rowCount()-1; row++)
{
    for(int column = 0;column< ui->tableWidget->columnCount()-1 ;column++)
    {
        headerString += ui->tableWidget->item(row,column)->text() +",";
    }
    headerString += "\r\n";
}
fprintf(f_out,"%s",headerString.toAscii().data());
fflush(f_out);
fclose(f_out);

QString fileName = appData + DIR+ "AISTABLE";
fileName = fileName + d_local.toString("_yyyy-MM-dd") + t_local.toString("_HH-mm-ss") + ".csv";
f_out = fopen(fileName.toAscii().data(), "wb+");
if (f_out == NULL) {
    return;
}

QString headerString = "d1,d2,d3,d4,d5,d6,d7,d8,d9,d10,d11\r\n";

for(int row = 0;row <ui->tableWidget->rowCount()-1; row++)
{
    for(int column = 0;column< ui->tableWidget->columnCount()-1 ;column++)
    {
        headerString += ui->tableWidget->item(row,column)->text() +",";
    }
    headerString += "\r\n";
}
fprintf(f_out,"%s",headerString.toAscii().data());
fflush(f_out);
fclose(f_out);

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I have created the Qtablewidget using Qt designer with rows = 300 and column = 12.
When I execute the above program, I get the following error:

Unhandled exception at 0x5463d72c in File.exe: 0xC0000005: Access violation reading location 0x00000000.

What is the problem for not getting output?