Cannot run a simple console program using QProcess

Question

I created a simple Qt app to compile a C++ file using QProcess. Now when I try to run the exe file from the app using QProcess, it doesn't run. When I tried to open the file manually, I got an error saying "libwinpthread-1.dll is missing".

Here's how I compiled the file-

QFileInfo finfo(fileName);
exeFileName = QFileInfo( QDir(finfo.path()), finfo.baseName() + ".exe").filePath();
QStringList arguments;
arguments << fileName << "-o" << exeFileName;
process->start(QString("g++"), arguments);

And, this is the code for running it -

QProcess *runProcess = new QProcess(this);
runProcess->setStandardInputFile(inputFilename);
runProcess->setStandardOutputFile(QFileInfo(exeFileName).path() + "/output.txt");
connect(runProcess, SIGNAL(finished(int)), this, SLOT(runComplete(int)));
runProcess->start(exeFileName);

Basically, I want to compile and run a C++ file, provide it sample input file and store the standard output in a new file. What is wrong with this code? Or any other way of doing it? I am working on windows 7. Also, I cannot understand why does the compiled program need that dll file when compiled from the Qt app and runs fine when compiled manually.

Just in case, this is the file I am trying to compile

//file.cpp
#include <iostream>

int main() {
    std::string s;
    std::cin >> s;
    std::cout << s;
    return 0;
}

score 3 · Answer 1 · answered Feb 12 '14 at 14:40

3

You are using API of QProcess in unexpected way. You need to create QStringList of args:

QStringList args;
args << fileName;
args << exeFileName;
...
compileProcess->start("g++", args);

answered Feb 12 '14 at 14:40

yshurik

772
5
12

I tried doing it that way but it didn't work due to spaces in file path. – Shubham Feb 12 '14 at 14:41
This way is actually better in handling spaces in arguments - no quotes needed, so you may have some another especiality with QProcess, try to check what is the PATH environment variable - then you may have some dlls not found – yshurik Feb 12 '14 at 14:45
@Shubham Are you absolutely sure that that's the case? Because it works for me. – Kuba hasn't forgotten Monica Feb 12 '14 at 14:45
@KubaOber Yes. My file was in a folder that had a space in its name. Didn't work – Shubham Feb 12 '14 at 14:47
@Shubham Again - it works for me on both Qt 4.8.5 and 5.2.1 on OS X. What version do you use, and on what platform? – Kuba hasn't forgotten Monica Feb 12 '14 at 14:50
@KubaOber I am using Qt 5.0.2 on windows 7. To specify the filename in arguments, i used `fileName` and `QFileInfo(fileName).path() + "/out.exe"` – Shubham Feb 12 '14 at 14:53
1

@KubaOber see this http://stackoverflow.com/questions/21722711/unable-to-start-g-using-qprocess?noredirect=1#comment32857165_21722711 – Shubham Feb 12 '14 at 14:57
@yshurik I still have the same problem on using `args`, the program compiles but doesn't run. I edited my question in response to that. – Shubham Feb 13 '14 at 06:36

Shubham · Accepted Answer · 2014-02-13T10:18:49.437

0

I seem to get it working by providing -static option while compiling the file, the exe file produced runs fine without demanding any external .dll file. But still, It doesn't run from QProcess.

edited Feb 13 '14 at 10:18

answered Feb 13 '14 at 10:06

Shubham

935
1
7
25

Cannot run a simple console program using QProcess

2 Answers2