How might I discover, at runtime, using Qt, if a user's system is Win 7-32 or Win7-64?
There is no way of doing it exclusively using Qt, AFAIK. Below is how you can do it.
#include <windows.h>
#include <tchar.h>
#include <QtCore/QSysInfo>
typedef enum { Win_64, Win_32, Error, Other } OsType;
typedef BOOL (WINAPI *LPFN_ISWOW64PROCESS) (HANDLE, PBOOL);
OsType checkOS() {
#ifndef Q_OS_WIN32
return Other;
#else
// An application compiled for 64 bits can only run on a 64 bit os,
// so no need to check any further.
if (QSysInfo::WordSize == 64) return Win7_64;
// A 32 bit application may be running on a 64 bit OS.
BOOL is64 = FALSE;
// IsWow64Process may not be available in kernel32 on all Windows versions, so we bind to it
// at runtime.
LPFN_ISWOW64PROCESS fnIsWow64Process;
fnIsWow64Process = (LPFN_ISWOW64PROCESS)
GetProcAddress(GetModuleHandle(TEXT("kernel32")),"IsWow64Process");
// No way it's a 64 bit OS if it doesn't have this API.
if (fnIsWow64Process == NULL) return Win_32;
// Note that GetCurrentProcess() can't fail.
if (!IsWow64Process(GetCurrentProcess(), &is64)) return Error; // The check has failed.
return is64 ? Win_64 : Win_32;
#endif
}
For the case of Qt 5 you can use QSysInfo static functions like prettyProductName() and currentCpuArchitecture().
Related
I want to be able to recover from a Segmentation Fault in MyApplication by catching the SIGSEGV and restarting QApplication. So for testing purposes I'm injecting a segmentation fault in my code.
The issue is that the signal handler that catches the SIGSEGV is getting a non-stop stream of SIGSEGVs. At first I thought it was the while loop in my main but it still happens even though I comment out the while loop. So my questions are simple: Is it even possible to recover from a Segmentation Fault in Qt? Why am I getting rolling SIGSEGVs non-stop?
#include <QApplication>
#include <QDebug>
#include "MyApplication.h"
#include <initializer_list>
#include <signal.h>
#include <unistd.h>
#include <stdio.h>
#define RESTART_CODE 1000
void catchUnixSignals(std::initializer_list<int> quitSignals)
{
auto handler = [](int sig) -> void
{
if (sig == SIGSEGV)
{
QCoreApplication::exit(RESTART_CODE);
}
else
{
QCoreApplication::quit();
}
};
sigset_t blocking_mask;
sigemptyset(&blocking_mask);
for (auto sig : quitSignals)
sigaddset(&blocking_mask, sig);
struct sigaction sa;
sa.sa_handler = handler;
sa.sa_mask = blocking_mask;
sa.sa_flags = 0;
for (auto sig : quitSignals)
sigaction(sig, &sa, nullptr);
}
int main(int argc, char *argv[])
{
catchUnixSignals({SIGSEGV, SIGQUIT, SIGINT, SIGTERM, SIGHUP, SIGKILL});
int i = 0;
do
{
QApplication app(argc, argv);
MyApp myapp;
MyApp.start();
app.exec();
if (app.exec() != RESTART_CODE) break;
} while(1);
return 0;
}
This does not directly answers your question, but is another way to achieve similar behavior.
To recover from a segmentation fault, an option is to use a watchdog, i.e. another independent process that checks the status of your main software and restarts it when needed.
When you start your software, you create another process that runs a 2nd software, the watchdog. Ensure to start it in "detached" mode to avoid that it gets closed if your main software crashes.
In the watchdog, frequently call "tasklist" on Windows or "ps" or "top" on Linux and parse the output to check whether your software is still running. OR, use a UDP or TCP port to communicate between the main software and the watchdog, to tell the watchdog that the main software is still running well.
In the watchdog, if the main software is no longer running, restart the main software process (also in detached).
CAUTION: You need to manage the case where the main software is exited correctly. In that case the main software should either kill the watchdog itself when exiting normally (calling "kill" on the pid), or send it a message so that the watchdog exits as well.
I'm trying to use QtDbus to communicate with interface provided by PowerManager in my system. My goal is very simple. I will be writing code which causes my system to hibernate using DBus interface.
So, I installed d-feet application to see what interfaces DBus is available on my system, and what I saw:
As we see, I have a few interfaces and methods from which I can choose something. My choice is Hibernate(), from interface org.freedesktop.PowerManagment
In this goal I prepared some extremely simple code to only understand mechanism. I of course used Qt library:
#include <QtCore/QCoreApplication>
#include <QtCore/QDebug>
#include <QtCore/QStringList>
#include <QtDBus/QtDBus>
#include <QDBusInterface>
int main(int argc, char **argv)
{
QCoreApplication app(argc, argv);
if (!QDBusConnection::sessionBus().isConnected()) {
fprintf(stderr, "Cannot connect to the D-Bus session bus.\n"
"To start it, run:\n"
"\teval `dbus-launch --auto-syntax`\n");
return 1;
}
QDBusInterface iface("org.freedesktop.PowerManagement" ,"/" , "" , QDBusConnection::sessionBus());
if(iface.isValid())
{
qDebug() << "Is good";
QDBusReply<QString> reply = iface.call("Methods" , "Hibernate");
if(reply.isValid())
{
qDebug() << "Hibernate by by " << qPrintable(reply.value());
}
qDebug() << "some error " << qPrintable(reply.error().message());
}
return 0;
}
Unfortunately I get error in my terminal:
Is good
some error Method "Methods" with signature "s" on interface "(null)" doesn't exist
So please tell me what's wrong with this code? I am sure that I forgot some arguments in function QDBusInterface::call() but what ?
When creating interface you have to specify correct interface, path, service. So that's why your iface object should be created like this:
QDBusInterface iface("org.freedesktop.PowerManagement", // from list on left
"/org/freedesktop/PowerManagement", // from first line of screenshot
"org.freedesktop.PowerManagement", // from above Methods
QDBusConnection::sessionBus());
Moreover, when calling a method you need to use it's name and arguments (if any):
iface.call("Hibernate");
And Hibernate() doesn't have an output argument, so you have to use QDBusReply<void> and you can't check for .value()
QDBusReply<void> reply = iface.call("Hibernate");
if(reply.isValid())
{
// reply.value() is not valid here
}
I wrote some demo app, that uses nacl_io sockets,
but bind fails with errno == EPERM
building with pepper_37,
Google Chrome 39.0.2171.95 (m)
OS Windows 7 or Server 2008 R2 SP1 64 bit
PNaCl translator version 0.1.0.13769
chrome flags:
--allow-nacl-socket-api=localhost --no-sandbox --enable-nacl
class ProxyTesterInstance : public pp::Instance
{
public:
explicit ProxyTesterInstance(PP_Instance instance, PPB_GetInterface get_interface) : pp::Instance(instance)
{
nacl_io_init_ppapi(instance, get_interface);
}
virtual ~ProxyTesterInstance() {}
virtual void HandleMessage(const pp::Var& var_message)
{
if (!var_message.is_string())
return;
std::string message = var_message.AsString();
if (message == kStartString)
{
reply(kReplyStartString);
int fd = socket( PF_INET, SOCK_STREAM, 0);
struct sockaddr_in myaddr;
myaddr.sin_family = PF_INET;
myaddr.sin_port = htons(50000);
inet_aton("0.0.0.0", &myaddr.sin_addr );
int res = bind(fd, (struct sockaddr*)&myaddr, sizeof(myaddr)); //returns -1
myaddr.sin_port = htons(80);
inet_aton("173.194.113.2", &myaddr.sin_addr );
res = connect(fd, (struct sockaddr*)&myaddr, sizeof(myaddr)); //returns 0
}
nacl_io assumes that it is being run on a worker thread, not the main thread. This is because many socket functions are blocking, but it is illegal to block the main thread in a NaCl application. Unfortunately, the error messages are not very clear explaining this constraint.
The easiest way to make this code work is to use the ppapi_simple library. It will initialize nacl_io for you and start running your code on a worker thread. At this point, you'll be able to make blocking calls (such as bind). It also gives you a main-like entry point instead of having to create a pp::Instance.
Take a look at some of the demos in the NaCl SDK (e.g. examples/demo/earth, examples/demo/pi_generator) for how to use ppapi_simple.
I am trying to compile some simple networking programs on freebsd 8 and running into compilation issues. I am creating a simple client-server programs but no function or structure from networking is not getting compiled.
For eg. I use standard socket() call to create a socket but I run into an error "Called object socket is not a function."
If I remove the network code then my toy program compiles. For simplicity I have just put a simple example which does not compile. :
#include <stdio.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
void main(){
int socket = socket(PF_INET,SOCK_STREAM,IPPROTO_TCP);
printf("Could create sockets without any issues.\n");
}
I compiled it with "cc toy_prog.c -lc" and gave me the mentioned error.
A very simple error. You have defined a local variable with the same name as the external function you are trying to call (socket). Try the following and you will get the same error:
int f()
{
return 0;
}
void main()
{
int f = f();
}
I am having problems with launching Nokia's own video player from my application that I just don't seem to be able to solve.
My first attempt included calling
Qt.openUrlExternally(url)
from QML and that seemed to do the trick just fine, except that it opened the browser every time and used it instead of the video-suite (native player).
Next I tried cuteTube -approach where I start new process like this:
QStringList args;
args << url;
QProcess *player = new QProcess();
connect(player, SIGNAL(finished(int, QProcess::ExitStatus)), player, SLOT(deleteLater()));
player->start("/usr/bin/video-suite", args);
That worked, except that it required video-suite to be closed upon calling player->start, otherwise it did nothing.
My third attempt involved starting the video-suite via QDBus, but that didn't work any better:
QList<QVariant> args;
QStringList urls;
urls << url;
args.append(urls);
QDBusMessage message = QDBusMessage::createMethodCall(
"com.nokia.VideoSuite",
"/",
"com.nokia.maemo.meegotouch.VideoSuiteInterface",
"play");
message.setArguments(args);
message.setAutoStartService(true);
QDBusConnection bus = QDBusConnection::sessionBus();
if (bus.isConnected()) {
bus.send(message);
} else {
qDebug() << "Error, QDBus is not connected";
}
The problem with this is that it requires video-suite to be up and running - autoStartService parameter didn't help either. If video-suite isn't running already, the call opens it just fine but, alas, no video starts to play.
Eventually I tried using also VideoSuiteInterface, but even having the program compile with it seemed to be difficult. When I eventually managed to compile and link all relevant libraries, the results didn't differ from option 3 above.
So, is there a way to use either VideoSuiteInterface directly or via DBus so that it would start video playback regardless of the current state of the application?
The solution was actually simpler than I really thought initially; the VideoSuiteInterface -approach worked after all. All it took was to use it properly. Here are the full sources should anyone want to try it themselves.
player.h:
#ifndef PLAYER_H
#define PLAYER_H
#include <QObject>
#include <maemo-meegotouch-interfaces/videosuiteinterface.h>
class Player : public QObject {
Q_OBJECT
private:
VideoSuiteInterface* videosuite;
public:
Player(QObject *parent = 0);
Q_INVOKABLE void play(QString url);
};
#endif // PLAYER_H
player.cpp:
#include "player.h"
#include <QObject>
#include <QStringList>
#include <QtDeclarative>
Player::Player(QObject *parent) : QObject(parent) {}
void Player::play(QString url) {
QList<QVariant> args;
QStringList urls;
urls << url;
args.append(urls);
videosuite = new VideoSuiteInterface();
videosuite->play(urls);
}
In addition you may want to connect some signals to make the UI more responsive, but basically that should do the trick.
Finally, you need to remember to add following to your .pro file and you are good to go:
CONFIG += videosuiteinterface-maemo-meegotouch