Unable to start g++ using QProcess

Question

I want to compile a c++ file from Qt application by using QProcess. But it is not working, I don't see any .o or .exe file generated by the compiler.

Here is what I am doing -

QProcess *process = new QProcess(this);
QString program = "g++";
QStringList arguments;
//fileName is fetched from QFileDialog
arguments << fileName << "-o" << QFileInfo(fileName).path() + QFileInfo(fileName).baseName() + ".exe";

errorFilename = QFileInfo(fileName).baseName() + "_error.txt";

process->setStandardOutputFile(errorFilename);

connect(process, SIGNAL(finished(int)), this, SLOT(compiled()));
process->start(program, arguments);

Pleae tell me what's wrong with this code. I am working on windows 7.

Exactly what happens? Do you get an error, if so what, and when (compiling or running the code)? — Mats Petersson, Feb 12 '14 at 08:47
@MatsPetersson The `errorFile` generated is empty. I don't see any errors. — Shubham, Feb 12 '14 at 08:49
@louissmr The `fileName` is set by `QFileDialog::getOpenFileName()`. — Shubham, Feb 12 '14 at 08:50
ok, but your actual path has any spaces on it? I have had issues with QProcess and paths with spaces as arguments in Windows. The process is lauched fine, but the arguments are not ok. — louissmr, Feb 12 '14 at 08:52
process->start(QString("g++ -o \"%1\" \"%2\" ").arg(fileName.path).arg(fileName+"exe"); — louissmr, Feb 12 '14 at 08:54
`QProcess` should wrap any arguments that have spaces inside quotes (http://qt-project.org/doc/qt-5.0/qtcore/qprocess.html#start). — Michael Burr, Feb 12 '14 at 09:00
Is `g++` in the `PATH` (in the environment of the Qt program)? What happen when you try to compile that same file with the same arguments from the command line? — Michael Burr, Feb 12 '14 at 09:04
@louissmr: actually, the start() overload taking QStringList() is usually more robust and to be preferred over manual quoting. — Frank Osterfeld, Feb 12 '14 at 11:16
@FrankOsterfeld yes, and I am using this method in Linux and MacOSX, but at least in some versions of Qt (I can't remember now the exact version number) is not working properly in Windows. — louissmr, Feb 12 '14 at 12:11

Michael Burr · Answer 1 · 2014-02-12T09:33:01.367

1

Keep in mind that errors don't go to stdout, they go to stderr. Try using:

process->setStandardErrorFile(errorFilename);

Also QFileInfo::path() won't have a path separator at the end, so you'll need to add one when concatenating the path with the base filename:

QFileInfo finfo(fileName);

arguments << fileName << "-o" << QFileInfo( QDir(finfo.path()), finfo.baseName() + ".exe").filePath();

edited Feb 12 '14 at 09:33

answered Feb 12 '14 at 09:01

Michael Burr

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Unable to start g++ using QProcess

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