Connect do not find slots under Q_OS_LINUX macro

IvanVa

I'm making an app who run both on windows and linux.
The linux version in detail must run an external process so i've created a QProcess object and relative slots enclosed into Q_OS_LINUX.

The problem is that the QObject::connect function cannot find the slots.
I've prepared a fresh-new mini app to demonstrate this, who show the problem (i'm running Ubuntu 16.04 X64, qt5.5.1)

MainWindow.h

#ifndef MAINWINDOW_H
#define MAINWINDOW_H

#include <QMainWindow>
#include <QProcess>

namespace Ui {
class MainWindow;
}

class MainWindow : public QMainWindow
{
    Q_OBJECT

public:
    explicit MainWindow(QWidget *parent = 0);
    ~MainWindow();
private slots:
    #ifdef Q_OS_LINUX
    void myFinishedSlot(int);
    #endif
private:
    Ui::MainWindow *ui;
    #ifdef Q_OS_LINUX
    QProcess *myProcess;
    #endif
};

#endif // MAINWINDOW_H

MainWindow.cpp

#include "mainwindow.h"
#include "ui_mainwindow.h"
#include <QDebug>

MainWindow::MainWindow(QWidget *parent) :
    QMainWindow(parent),
    ui(new Ui::MainWindow)
{
    ui->setupUi(this);
    #ifdef Q_OS_LINUX
    myProcess=new QProcess(this);
    connect(myProcess,SIGNAL(finished(int)),this,SLOT(myFinishedSlot(int)));
    myProcess->start("7za");
    #endif
}

MainWindow::~MainWindow()
{
    delete ui;
}

#ifdef Q_OS_LINUX
void MainWindow::myFinishedSlot(int retValue){
    qDebug()<<retValue;
}
#endif

Once started, in the application output area i can see:

QObject::connect: No such slot MainWindow::myFinishedSlot(int) in ../slot_test/mainwindow.cpp:12
QObject::connect:  (receiver name: 'MainWindow')

I cannot figure out why i get this message. Obviously, removing Q_OS_LINUX limitation make the app work but this is not the wanted solution ( it make process and slots also included into the windows binaries).

Ivan.

VRonin

add -DQ_OS_LINUX when you call moc

you can achieve it adding this to the .pro file

unix:!macx {
QMAKE_MOC = $$QMAKE_MOC -DQ_OS_LINUX
}

as a side comment: you can use KArchive to handle 7zip (but not only 7zip) archives in a platform independent way rather than calling 7za

SGaist

Hi and welcome to devnet,

Not a direct answer but since it's something private anyway, a lambda might be a better choice in your case thus avoiding the need for the macro in the header.

hskoglund

This post is deleted!

IvanVa

@VRonin said in connect do not find slots under Q_OS_LINUX macro:

add -DQ_OS_LINUX when you call moc

you can achieve it adding this to the .pro file

Adding -DQ_OS_LINUX cause a redeclaration warning, but following your idea with this code in the .pro file

!win32{
    DEFINES += MOC_OS_LINUX
}

and then in the mainwindows.h file

#if defined(Q_OS_LINUX) || defined(MOC_OS_LINUX)
void myFinishedSlot(int);
#endif

Works without warnings. May not be eye-friendly but as a ''''''temporary''''' solution is acceptable

To the side comment: my goal is so basic that just by calling 7za with two parameters is all i need. Wrote that code faster than a running Bolt.

EDIT: you wrote another piece of post while i was typing previous text. I'm now trying with your suggestion

EDIT2: your solution do not work, i suspect QMAKE_MOC is ignored by the system since the -DQ_OS_LINUX do not appear in the parameter list when moc is called during build. Also tried to comment out 'unix:!macx' condition, but same result. Temporary i'll use my previous solution

kshegunov

This is a bad way of designing an API!
Here's what the user of your library is supposed to do for each of the OSes:

#ifdef Q_OS_LINUX
    myobject.lunuxOnySlot();
#else
    myobject.slotNotInLunux();
#endif

?

Stick to what @SGaist wrote and don't ifdef the public API, hide the private implementation details (the OS dependence) in a lambda or behind the PIMPL idiom instead.

Kind regards.