qDebug messages not showing in console window with qInstallMessageHandler implemented

jenschucksgs

My source code file:

#include <QCoreApplication>
#include <QtDebug>
#include <QtGlobal>

#include <stdio.h>
#include <stdlib.h>

void myMessageOutput(QtMsgType type, const QMessageLogContext &context, const QString &msg)
{
    QByteArray localMsg = msg.toLocal8Bit();
    fprintf(stderr, "MESSAGE (%s:%u %s): %s\n", context.file, context.line, context.function, localMsg.constData());
    fflush(stderr);
}

int main(int argc, char **argv)
{
    QCoreApplication app(argc, argv);
    qInstallMessageHandler(myMessageOutput);
    qDebug() << "Printed in the console";
    qInstallMessageHandler(0);
    qDebug() << "Also printed in the console";
    return app.exec();
}

My CMakeLists.txt file:

cmake_minimum_required( VERSION 3.10 )

SET( BIN_NAME test_debug )
INCLUDE( ../../cyflex_qt.cmake OPTIONAL )

project( "${BIN_NAME}" )

find_package(Qt5 REQUIRED COMPONENTS Core Widgets )

set( CMAKE_INCLUDE_CURRENT_DIR ON )
set( CMAKE_AUTOMOC ON )
set( CMAKE_AUTOUIC ON )

set( CMAKE_BINARY_OUTPUT_DIRECTORY ${TARGET_BINPATH} )

SET( ${BIN_NAME}_SOURCES     main.cpp  )

add_executable( ${BIN_NAME} ${${BIN_NAME}_SOURCES} )

target_link_libraries(${BIN_NAME} Qt5::Widgets )

We have migrated our code from Scientific Linux (32bit) to Oracle Linux (64bit). When I run this exact code on my 32bit system in qt5, I get the qDebug messages at the console as I expect. When I run this code on my 64bit system in qt5, no messages get displayed.

If I create a ~/.config/QtProject/qtlogging.ini file on my 64bit system. The debug messages are printed to the console. However, for a GUI application, there are many debug messages printed besides the expected ones.

Example ~/.config/QtProject/qtlogging.ini

[Rules]
*.debug=true

How do I only get the expected qDebug statements written to the console? Is there something I need to do without creating the qtlogging.ini file?

Christian Ehrlicher

Works fine for me with Qt5.15.2. Are you sure e.g. QT_NO_DEBUG_OUTPUT is not set in your setup somewhere?