segfault when reading QTextStream - qt

Question

Context:
I have a set of file like that:
alias
USER = usr_name
PASSWORD = pass
...
alias2
...
I have a combobox to choose which file to display in a qtableview. The below is the slot called when the value of the combobox changes.
void paramTableModel::switchTable(QString env)
{
// is there an environment defined
// --------------------------------------
if(env.compare("") != 0)
{
// does the param file exist ?
// ---------------------------
QString file_path = "/path/to/" + env + "/path/to/file;
QFile param_file(file_path);
if( param_file.exists() && param_file.open(QIODevice::ReadOnly))
{
QString program_decrypt = "/path/to/decrypt";
QStringList args;
args << file_path;
QProcess* process = new QProcess();
process->setReadChannel(QProcess::StandardOutput);
process->start(program_decrypt,args);
process->waitForFinished(-1);
QTextStream in(&process->readAll());
//start resetting model (notify the view )
beginResetModel();
this->table.clear();
std::set<QString> uniq;
// parse file to model
// -------------------
while( !in.atEnd() )
{
QString line = in.readLine();
// some new UT ?
// -------------------
if( !line.isNull() && line.trimmed().compare("") != 0 && !line.contains("="))
{
line = line.trimmed();
std::vector<QString> row;
if(uniq.find(line) == uniq.end())
{
uniq.insert(line);
row.push_back(line);
QString user_line = in.readLine().trimmed();
QString password_line = in.readLine().trimmed();
QString server_line = in.readLine().trimmed();
if( user_line.startsWith("USER") )
{
user_line = user_line.split('=').at(1).trimmed();
}
if( password_line.startsWith("PASSWORD") )
{
password_line = password_line.split('=').at(1).trimmed();
}
if( server_line.startsWith("SERVER") )
{
server_line = server_line.split('=').at(1).trimmed();
}
row.push_back(user_line);
row.push_back(password_line);
row.push_back(server_line);
this->table.push_back(row);
}
else
{
QMessageBox msgBox;
msgBox.setText(QString("%1 is already defined, ingnoring").arg(line));
msgBox.exec();
}
}
}
param_file.close();
endResetModel();
delete process;
}
}
}
Most of the time, my view is properly refreshed. And from time to time, this line segfaults:
QString line = in.readLine();
I have found no pattern to reproduce the bug in a systematic way. I can click back and forth between two files in the combobox, it will work ten, twelve, twenty times and then segfault.
EDIT:
This does work.
void paramTableModel::switchTable(QString env)
{
// is there an environment defined
// --------------------------------------
if(env.isEmpty())
return;
// does the param file exist ?
// --------------------------------
QString file_path = "/path/to/env/" + env + "/path/to/file.dat";
QFile param_file(file_path);
if( param_file.exists() && param_file.open(QIODevice::ReadOnly))
{
// Call QProcess, fx_decrypt, read standard output
QString program_decrypt = "/path/to/decrypt";
QStringList args;
args << file_path;
QProcess process;
process.setReadChannel(QProcess::StandardOutput);
process.start(program_decrypt,args);
process.waitForFinished(-1);
//QTextStream in(&process->readAll());
QString out = process.readAll();
QStringList list_out = out.split("\n",QString::SkipEmptyParts);
//start resetting model (notify the view )
beginResetModel();
this->table.clear();
std::set<QString> uniq;
// parse file to model
// -----------------------
//while( !in.atEnd() )
int counter = 0;
while(counter < list_out.size())
{
//QString line = in.readLine();
QString line = list_out.at(counter);
// some new UT ?
// -------------------
if( !line.isNull() && !line.trimmed().isEmpty() != 0 && !line.contains("="))
{
line = line.trimmed();
std::vector<QString> row;
if(uniq.find(line) == uniq.end())
{
uniq.insert(line);
row.push_back(line);
/**QString user_line = in.readLine().trimmed();
QString password_line = in.readLine().trimmed();
QString server_line = in.readLine().trimmed();*/
QString user_line = list_out.at(++counter).trimmed();
QString password_line = list_out.at(++counter).trimmed();
QString server_line = list_out.at(++counter).trimmed();
if( user_line.startsWith("USER") )
{
user_line = user_line.split('=').at(1).trimmed();
}
if( password_line.startsWith("PASSWORD") )
{
password_line = password_line.split('=').at(1).trimmed();
}
if( server_line.startsWith("SERVER") )
{
server_line = server_line.split('=').at(1).trimmed();
}
row.push_back(user_line);
row.push_back(password_line);
row.push_back(server_line);
this->table.push_back(row);
}
else
{
QMessageBox msgBox;
msgBox.setText(QString("%1 is already defined, ingnoring").arg(line));
msgBox.exec();
}
}
++counter;
}
endResetModel();
}
}
Trying to get the why of the bug, following #Kuba Ober suggestion
I've tried to copy the first version into a main function looping indefinitely over all my environments:
But it does work fine!
#include <QtCore/QCoreApplication>
#include <QProcess>
#include <QTextStream>
#include <set>
#include <vector>
#include <QDebug>
#include <QFile>
#include <deque>
#include <QDir>
#include <QStringList>
std::deque< std::vector < QString > > table;
void f( QString file_path )
{
// does the param file exist ?
// --------------------------------
QFile param_file(file_path);
if( param_file.exists() && param_file.open(QIODevice::ReadOnly))
{
// Call QProcess, fx_decrypt, read standard output
QString program_decrypt = "/path/to/decrypt";
QStringList args;
args << file_path;
QProcess* process = new QProcess();
process->setReadChannel(QProcess::StandardOutput);
process->start(program_decrypt,args);
process->waitForFinished(-1);
QTextStream in(&process->readAll());
//start resetting model (notify the view )
table.clear();
std::set<QString> uniq;
// parse file to model
// -----------------------
while( !in.atEnd() )
{
QString line = in.readLine();
// some new UT ?
// -------------------
if( !line.isNull() && line.trimmed().isEmpty() != 0 && !line.contains("="))
{
line = line.trimmed();
std::vector<QString> row;
if(uniq.find(line) == uniq.end())
{
uniq.insert(line);
row.push_back(line);
QString user_line = in.readLine().trimmed();
QString password_line = in.readLine().trimmed();
QString server_line = in.readLine().trimmed();
if( user_line.startsWith("USER") )
{
user_line = user_line.split('=').at(1).trimmed();
}
if( password_line.startsWith("PASSWORD") )
{
password_line = password_line.split('=').at(1).trimmed();
}
if( server_line.startsWith("SERVER") )
{
server_line = server_line.split('=').at(1).trimmed();
}
row.push_back(user_line);
row.push_back(password_line);
row.push_back(server_line);
table.push_back(row);
}
else
{
qDebug() << QString("%1 is already defined, ingnoring").arg(line);
}
}
}
param_file.close();
delete process;
}
}
QStringList getEnvList()
{
QDir dir("/path/to/env/");
QStringList list_env;
foreach(QString folder, dir.entryList(QStringList(),QDir::AllDirs | QDir::NoDotAndDotDot))
{
QFile app_file( dir.absolutePath() + '/' + folder + '/' + "file.dat" );
if (app_file.exists())
{
list_env.push_back(folder);
}
}
return list_env;
}
int main(int argc, char *argv[])
{
QCoreApplication a(argc, argv);
int counter = 0;
while(true)
{
foreach ( QString s, getEnvList() )
{
qDebug() << counter++;
qDebug() << s;
f(s);
}
}
return a.exec();
}
I have no idea, why the two below codes never crash while the first one does...