I'm trying to write a simple example of loading a dll file, and the load fails.
I'm using qt 5.1.1 qt creator 3.0.1.
my compiler is: Microsoft Visual C++ Compiler 11.0 (amd64)
the pro file:
QT += core
TARGET = rrrr
SOURCES += main.cpp
the main file is:
#include <QLibrary>
int main()
{
bool is;
QLibrary lib("C:\\A.dll");
is = lib.load();
is = lib.isLoaded();
return 0;
}
The A.dll file of-course exists inside C.
I get the value false for the variable "is" while debbuging.
Related
For some reason I am unable to load my plugins anymore, although it has worked previously. I have a plugin loader code in my MainWindow, which is supposed to load every .dll found in a specific folder. The MainWindow Code contains the following:
Interface
#ifndef PLUGININTERFACE_H
#define PLUGININTERFACE_H
#include <QtPlugin>
// forward declarations
class MainWindow;
struct P3DData;
class PluginInterface
{
public:
virtual bool createPublisher(MainWindow*, P3DData*) = 0;
};
#define PLUGIN_INTERFACE_iid "PluginInterface"
Q_DECLARE_INTERFACE(PluginInterface, PLUGIN_INTERFACE_iid)
#endif // PLUGININTERFACE_H
loadPlugins()
bool MainWindow::loadPlugins()
{
QDir pluginsDir(qApp->applicationDirPath());
pluginsDir.cd("plugins");
const auto entryList = pluginsDir.entryList(QDir::Files);
for(const QString &fileName : entryList)
{
QString dllPath = pluginsDir.absoluteFilePath(fileName);
QPluginLoader* loader = new QPluginLoader(dllPath);
loaderList.push_back(loader);
QObject *plugin = loader->instance();
if (plugin)
{
pluginList.push_back(qobject_cast<PluginInterface *>(plugin));
pluginList.last()->createPublisher(this, simDataPtr);
pluginCount++;
continue;
}
else
{
qDebug() << "[PluginLoader] '" + fileName + "': " + loader->errorString();
delete loaderList.takeLast();
}
}
}
Besides my MainWindow, there is another subdir in my project, which is the plugin "Position". The plugin is deployed into the correct "plugins" folder, which the loadPlugin() method from the MainWindow iterates through. The plugin uses following code to implement the interface:
#include <QObject>
#include "MainWindow.h"
class PositionPublisher : public QObject, PluginInterface
{
Q_OBJECT
Q_PLUGIN_METADATA(IID "PluginInterface")
Q_INTERFACES(PluginInterface)
public:
PositionPublisher();
~PositionPublisher();
bool createPublisher(MainWindow* _window, P3DData* _simDataPtr) override;
//...
};
When trying to run loadPlugins() now, it checks the correct Position.dll file but the "if(plugin)" part returns false and loader->errorString() is executed giving the following error:
[PluginLoader] 'Position.dll': Cannot load library
F:\DEV\build\simNET\bin\plugins\Position.dll: Cannot find the
specified module.
I have already checked and tried the following:
the Plugins folder actually contains the Position.dll file
both projects (MainWindow and Plugin) are built in release mode
the dependencies of the plugin (two libs) exist and the specified path in the pro file is correct
.pro file of plugin:
QT += widgets
TEMPLATE = lib
CONFIG += c++11
CONFIG += plugin
CONFIG += release
SOURCES += \
Position.cpp \
PositionPubSubTypes.cpp \
PositionPublisher.cpp
HEADERS += \
Position.h \
PositionPubSubTypes.h \
PositionPublisher.h
DISTFILES += \
Position.idl
INCLUDEPATH += ../../application
TARGET = $$qtLibraryTarget(Position)
DESTDIR = ../../bin/plugins
INCLUDEPATH += "F:/DEV/prog/FastRTPSv1.5/include"
DEPENDPATH += "F:/DEV/prog/FastRTPSv1.5/include"
LIBS += -L"F:/DEV/prog/FastRTPSv1.5/lib/x64Win64VS2015" -lfastrtps-1.5
PRE_TARGETDEPS += F:/DEV/prog/FastRTPSv1.5/lib/x64Win64VS2015/fastrtps-1.5.lib
INCLUDEPATH += 'F:/Programme/Prepar3D v4/SDK/inc/SimConnect'
DEPENDPATH += 'F:/Programme/Prepar3D v4/SDK/inc/SimConnect'
LIBS += -L'F:/Programme/Prepar3D v4/SDK/lib/SimConnect' -lSimConnect
PRE_TARGETDEPS += 'F:/Programme/Prepar3D v4/SDK/lib/SimConnect/SimConnect.lib'
Does anyone have an idea why it does not load the plugin??
Qt plugin loader is trying to tell you that a Qt module used in your plugin doesn't exist so first you need to check which Qt modules your plugin depends on then,
If you're trying to run the application from Qt Creator itself, and it gives you this error, then maybe the DLL file got deleted for some reason or you're trying to use the plugin with a Qt version that doesn't have its needed modules. (for example, Qt6 doesn't contain the QtSerialPort module but Qt5 did (at the time of writing this)).
If you're trying to run the application directly outside Qt Creator then you need to copy the required module's dll file into your applications root directory.
When I call the embedded python from my c++ app, the application crashes. Something in _PyCodec_Lookup is not working. Debugging seems to indicate the error comes from this line in file codecs.c:
PyInterpreterState *interp = _PyInterpreterState_GET_UNSAFE();
if (interp->codec_search_path == NULL && _PyCodecRegistry_Init())
goto onError;
interp->codec_search_path is NULL and _PyCodecRegistry_Init() returns -1.
This problems is already known; Solutions like removing python27, or setting environment variables PYTHONPATH or PYTHONHOME to either "" or the src path do not work.
I link to cpython version 3.8.0a3 which I've compiled with the included scripts inside the PCBUILD folder, using the same compiler as my applications (MSVC 15 2017).
The OS is windows 8.1 64 bit.
My application links to the produced binary python38.dll / python38.lib successfully but then crashes at runtime, and I have no idea what might cause the trouble - people suggest the environment is polluted, but it must not depend on the system's environment. How would I confidently ship the app to other people's computers? Did I maybe miss some compile flags or defines?
I'm sure you are, but you are doing this after Py_Initialize ?
I include the python3.8 dll but when starting up I take the executable full
path and then add that to the python path (the code below is not tested but
it's roughly what I do)
void py_add_to_path (const char *path)
{
PyObject *py_cur_path, *py_item;
char *new_path;
int wc_len, i;
wchar_t *wc_new_path;
char *item;
new_path = strdup(path);
py_cur_path = PySys_GetObject("path");
for (i = 0; i < PyList_Size(py_cur_path); i++) {
char *tmp = strappend(new_path, PATHSEP);
myfree(new_path);
new_path = tmp;
py_item = PyList_GetItem(py_cur_path, i);
if (!PyUnicode_Check(py_item)) {
continue;
}
item = py_obj_to_str(py_item);
if (!item) {
continue;
}
tmp = strappend(new_path, item);
free(new_path);
new_path = tmp;
free(item);
}
/* Convert to wide chars. */
wc_len = sizeof(wchar_t) * (strlen(new_path) + 1);
wc_new_path = (wchar_t *) malloc(wc_len, "wchar str");
mbstowcs(wc_new_path, new_path, wc_len);
PySys_SetPath(wc_new_path);
}
Seems a bit old now but looks like there is need to add the Lib folder including all the python system files to the search paths of the application.
Take a look at this Python port for UWP
It has an embedded python34app.zip that includes the codec files.
all
I'm trying to create ActiveX server with Qt5.2.0.
According to some pieces of information I have, to create a simple ActiveX server (which exports one object) it's enough to:
have such .pro file
TEMPLATE = lib
CONFIG += dll axserver
TARGET = simpleServer
greaterThan(QT_MAJOR_VERSION, 4): QT += widgets
QT += core
RC_FILE = qaxserver.rc
DEF_FILE = qaxserver.def
HEADERS += myserver.h
SOURCES += main.cpp
SOURCES += myserver.cpp
have such main.cpp file
#include "ActiveQt/QAxFactory"
#include "myserver.h"
QAXFACTORY_DEFAULT( MyServer, 5 id's )
the class should inherit QWidget and QAxBindable
there should be file qaxserver.rc. in my case it's content is 1 TYPELIB "simpleServer.pro"
there should be fie qaxserver.def with default contents:
; mfc_test.def : Declares the module parameters.
EXPORTS
DllCanUnloadNow PRIVATE
DllGetClassObject PRIVATE
DllRegisterServer PRIVATE
DllUnregisterServer PRIVATE
DumpIDL PRIVATE
the problem is that these 5 names are undefined for Visual Studio's linker.
How to solve the problem?
the error is:
error LNK2001: unresolved external symbol DllCanUnloadNow
need to add QT += axserver in .pro file
I am new to QT and need to build an app with an app-indicator. As QT seems easier than GTK+, I am making it in QT.
I would mention that I have sni-qt installed and app indicators of vlc and skype appear normal on the panel. I am using QT5 on Ubuntu 13.04 64-bit.
I followed this tutorial step by step: http://qt-project.org/doc/qt-4.8/desktop-systray.html
But when I run it, here's how it appears (The cross is the icon I am using):
How do I fix this?
I'm afraid that Qt5 is not supported by sni-qt at the moment, so you either have to wait for a new release that will support it, or code it using gtk+ and libappindicator using this guide. There are even examples for various of languages. Since Qt5 also distributes GLib events that makes the integration a lot more easier. First you need to find out whether you're running on Unity or not (to support more desktops than just unity), that you can do by retrieving XDG_CURRENT_DESKTOP environment variable and if it returns Unity you create appindicator, otherwise create QSystemTrayIcon.
First you need to include required headers:
#undefine signals
extern "C" {
#include <libappindicator/app-indicator.h>
#include <gtk/gtk.h>
}
#define signals public
Since app-indicator directly uses "signals" name we need to undefine the default Qt "keyword" signals which normally translates to public. Then, since we're coding C++ and libappindicator is coded in C we need to use extern "C" not to use C++ name mangling.
Next create the AppIndicator/QSystemTrayIcon based on what desktop are we on:
QString desktop;
bool is_unity;
desktop = getenv("XDG_CURRENT_DESKTOP");
is_unity = (desktop.toLower() == "unity");
if (is_unity) {
AppIndicator *indicator;
GtkWidget *menu, *item;
menu = gtk_menu_new();
item = gtk_menu_item_new_with_label("Quit");
gtk_menu_shell_append(GTK_MENU_SHELL(menu), item);
g_signal_connect(item, "activate",
G_CALLBACK(quitIndicator), qApp); // We cannot connect
// gtk signal and qt slot so we need to create proxy
// function later on, we pass qApp pointer as an argument.
// This is useful when we need to call signals on "this"
//object so external function can access current object
gtk_widget_show(item);
indicator = app_indicator_new(
"unique-application-name",
"indicator-messages",
APP_INDICATOR_CATEGORY_APPLICATION_STATUS
);
app_indicator_set_status(indicator, APP_INDICATOR_STATUS_ACTIVE);
app_indicator_set_menu(indicator, GTK_MENU(menu));
} else {
QSystemTrayIcon *icon;
QMenu *m = new QMenu();
m->addAction(tr("Quit"), qApp, SLOT(quit()));
}
Finally we create the proxy function to call Qt signal from it, to declare the function we need to use extern "C" so there will not be any undefined behaviour.
extern "C" {
void quitIndicator(GtkMenu *, gpointer);
}
Now the proxy function:
void quitIndicator(GtkMenu *menu, gpointer data) {
Q_UNUSED(menu);
QApplication *self = static_cast<QApplication *>(data);
self->quit();
}
Just wanted to add, for anyone that is using Qt and trying to show a app indicator in Ubuntu 13+ as others have mentioned sni-qt is not working, I was able to use the above reply to make a Qt app that works, still trying to get the icon to change and show popup messages, but this is a great start, once i get the icon and message to work i might post it out on my site Voidrealms.com:
Be sure to do sudo apt-get install libappindicator-dev
Make a new project with a QDialog in it and modify as seen below:
Pro file:
#-------------------------------------------------
#
# Project created by QtCreator 2014-03-28T20:34:54
#
#-------------------------------------------------
QT += core gui
greaterThan(QT_MAJOR_VERSION, 4): QT += widgets
TARGET = PluginServiceGUI
TEMPLATE = app
# includes for the libappindicator
# /usr/lib/x86_64-linux-gnu libglib-2.0.a
INCLUDEPATH += "/usr/include/libappindicator-0.1"
INCLUDEPATH += "/usr/include/gtk-2.0"
INCLUDEPATH += "/usr/include/glib-2.0"
INCLUDEPATH += "/usr/lib/x86_64-linux-gnu/glib-2.0/include"
INCLUDEPATH += "/usr/include/cairo"
INCLUDEPATH += "/usr/include/pango-1.0"
INCLUDEPATH += "/usr/lib/x86_64-linux-gnu/gtk-2.0/include"
INCLUDEPATH += "/usr/include/gdk-pixbuf-2.0"
INCLUDEPATH += "/usr/include/atk-1.0"
LIBS += -L/usr/lib/x86_64-linux-gnu -lgobject-2.0
LIBS += -L/usr/lib/x86_64-linux-gnu -lappindicator
LIBS += -L/usr/lib/x86_64-linux-gnu -lgtk-x11-2.0
#These seem to not be needed
#LIBS += -L/usr/lib/x86_64-linux-gnu -lcairo
#LIBS += -L/usr/lib/x86_64-linux-gnu -lpango-1.0
#LIBS += -L/usr/lib/x86_64-linux-gnu -lglib-2.0
# end incudes for libappindicator
SOURCES += main.cpp\
dialog.cpp
HEADERS += dialog.h
FORMS += dialog.ui
RESOURCES += \
resources.qrc
In the main.cpp
#include "dialog.h"
#include <QApplication>
#include <QtGui>
#include <QSystemTrayIcon>
#include <QMessageBox>
#include <QSystemTrayIcon>
#include <QMenu>
// http://stackoverflow.com/questions/17193307/qt-systray-icon-appears-next-to-launcher-on-ubuntu-instead-of-on-the-panel
// requires libappindicator-dev
// sudo apt-get install libappindicator-dev
// installs the headers in: /usr/include/libappindicator-0.1/libappindicator
#undef signals
extern "C" {
#include <libappindicator/app-indicator.h>
#include <gtk/gtk.h>
void quitIndicator(GtkMenu *, gpointer);
}
#define signals public
void quitIndicator(GtkMenu *menu, gpointer data) {
Q_UNUSED(menu);
QApplication *self = static_cast<QApplication *>(data);
self->quit();
}
void ShowUnityAppIndicator()
{
AppIndicator *indicator;
GtkWidget *menu, *item;
menu = gtk_menu_new();
item = gtk_menu_item_new_with_label("Quit");
gtk_menu_shell_append(GTK_MENU_SHELL(menu), item);
g_signal_connect(item, "activate",
G_CALLBACK(quitIndicator), qApp); // We cannot connect
// gtk signal and qt slot so we need to create proxy
// function later on, we pass qApp pointer as an argument.
// This is useful when we need to call signals on "this"
//object so external function can access current object
gtk_widget_show(item);
indicator = app_indicator_new(
"unique-application-name",
"indicator-messages",
APP_INDICATOR_CATEGORY_APPLICATION_STATUS
);
app_indicator_set_status(indicator, APP_INDICATOR_STATUS_ACTIVE);
app_indicator_set_menu(indicator, GTK_MENU(menu));
}
void ShowQtSysTray(QApplication* app, QDialog* dialog)
{
Q_INIT_RESOURCE(resources);
if (!QSystemTrayIcon::isSystemTrayAvailable()) {
QMessageBox::critical(0, QObject::tr("Systray"),
QObject::tr("I couldn't detect any system tray "
"on this system."));
}
QApplication::setQuitOnLastWindowClosed(false);
QSystemTrayIcon* trayIcon = new QSystemTrayIcon(dialog);
QAction* Action = new QAction("hello", dialog);
QMenu* trayIconMenu = new QMenu(dialog);
trayIconMenu->addAction("Quit", app, SLOT(quit()));
trayIconMenu->addAction(Action);
trayIcon->setContextMenu(trayIconMenu);
trayIcon->setIcon(QIcon (":/icons/Icons/accept.png"));
trayIcon->show();
trayIcon->showMessage("Title","Message");
}
int main(int argc, char *argv[])
{
QApplication a(argc, argv);
Dialog w;
//Determine the desktop type
QString desktop;
bool is_unity;
desktop = getenv("XDG_CURRENT_DESKTOP");
is_unity = (desktop.toLower() == "unity");
if(is_unity)
{
ShowUnityAppIndicator();
}
else
{
//Show the SystemTrayIcon the Qt way
ShowQtSysTray(&a, &w);
}
// w.show();
return a.exec();
}
I've just installed Qt 4.7.4 and trying to make a simple Qt App that uses Qt DLL. I added export/import in a class in DLL through ifdef as usual but when compiling App I het unresolved references. I also set that App depends on the DLL.
Here are the main files:
Lib.pro
QT -= gui
TARGET = Lib
TEMPLATE = lib
DEFINES += LIB_LIBRARY
SOURCES += lib.cpp
HEADERS += lib.h\
Lib_global.h
symbian {
MMP_RULES += EXPORTUNFROZEN
TARGET.UID3 = 0xE10C4E25
TARGET.CAPABILITY =
TARGET.EPOCALLOWDLLDATA = 1
addFiles.sources = Lib.dll
addFiles.path = !:/sys/bin
DEPLOYMENT += addFiles
}
unix:!symbian {
maemo5 {
target.path = /opt/usr/lib
} else {
target.path = /usr/lib
}
INSTALLS += target
}
App.pro
QT += core gui
TARGET = App
TEMPLATE = app
SOURCES += main.cpp\
mainwindow.cpp
HEADERS += mainwindow.h
FORMS += mainwindow.ui
lib.h
#ifndef LIB_H
#define LIB_H
#include "Lib_global.h"
#include <QString>
class LIBSHARED_EXPORT Lib {
public:
Lib();
~Lib();
QString Hello(QString a);
};
#endif // LIB_H
Lib_global.h
#ifndef LIB_GLOBAL_H
#define LIB_GLOBAL_H
#include <QtCore/qglobal.h>
#if defined(LIB_LIBRARY)
# define LIBSHARED_EXPORT Q_DECL_EXPORT
#else
# define LIBSHARED_EXPORT Q_DECL_IMPORT
#endif
#endif // LIB_GLOBAL_H
What's wrong with this code? Why is it unresolved reference?
In App I just include "../Lib/lib.h" and try to use the class.
What looks to be missing is the link between your application and your dynamic library.
I usually do something like this for my desktop (linux) apps:
INCLUDEPATH += ./include
LIBS += -L./lib -lLib
Where:
INCLUDEPATH defines the path to where your shared library .h files are located.
LIBS defines the path to where your built library is.
You can find the relevant documentation here: QMake - Declaring Other Libraries
Updated:
I was able to build the project (Linux Qt v4.7.4) and link to the library using the code you posted. I will try to clarify as my response may not be entirely clear.
The INCLUDEPATH and LIBS variables must be added to the App.pro file.
For the linker to properly find the library the paths must be adjusted to the paths you are using for your project:
LIBS += -L PATH -l LIBNAME
Supposing your folder structure is similar to the following:
Project
|_ Lib (your sharded library project files)
|_ App (your application project files)
You would adjust the variables like so:
INCLUDEPATH += ../Lib
LIBS += -L../Lib -lLib
Note that you link differently depending on your platform, you can do something like this to cover Windows and Linux:
unix {
INCLUDEPATH += ../Lib
LIBS += -L../Lib -lLib
}
win32 {
INCLUDEPATH += ../Lib
LIBS += ../Lib.lib
}