It's just plain luck my program is so simple, so I eventually found out what causes the mysterious log message. My program log looks like this:
Debugging starts
failed to start
Debugging has finished
Which happens after:
camera = new QCamera(QCameraInfo::defaultCamera());
// see http://omg-it.works/how-to-grab-video-frames-directly-from-qcamera/
camera->setViewfinder(frameGrabber = new CameraFrameGrabber());
camera->start();
The start() method causes this message in console. Now the meaning of the message is obvious, what it's not very helpful. What steps should I take to troubleshoot it?
Reasons for this might differ, but in my case it was simply because I provided invalid QCameraInfo. The culprit is that QCameraInfo::defaultCamera() might return invalid value if Qt fails to detect any cameras on your system, which unfortunately happens even if cameras are present.
Related
I'm currently programming an SDL Network Game, everything is perfect ... But my game only runs at 30fps, so I ran a Very Sleepy analysis.
First strange effect, very sleepy increase the perfs of my Game to 60Fps ... ( Why ? )
And secondly, there is a lot of SDL_LogCritical calls ( you can get the report here : http://puu.sh/gauEi/9a852462e6.png ). And nothing is shown in the console.
( I also use SDLNet, with TCP protocol, there is no packet loose ).
Moreover, I overwritten the output for SDL Logs :
void log(void* userdata, int category, SDL_LogPriority priority, const char* message) {
std::cout << "Log : " << message << std::endl;
}
int main(int argc, char **argv) {
SDL_Init(SDL_INIT_EVERYTHING);
SDLNet_Init();
SDL_LogSetOutputFunction(log, NULL);
SDL_LogCritical(1, "TEST LOG");
}
And I can see the "TEST LOG" in the console. So the SDL_LogCritical which consumme 30% doesn't output everything .
I don't know what's wrong, but frequent calls to a logging function indicate that something is wrong and SDL tries to tell you about it. However, the lack of output might be caused by you explicitely or implicitely disable logging to the console. Your use of Network might indicate your not looking at the right console to see these warnings. It's all a bit hard to diagnose with the lack of information given.
Performance increase due to debugging is strange, but can often be explained by the fact that the debugger doesn't use exactly the same environment as you do when running normally.
OK, so you're not seeing output when something else calls SDL's log functionality. This points to the messages being logged somehow being below necessary priority. Compare SDL's source code to find out how that could be happening. Maybe you should, at this point, use a debugger to set breakpoints.
I am using CPN Tools to model a distributed system. CPN Tools uses CPN ML an extension of SML. The project homepage is: cpntools.org
I started with a simple model and when I try to make a particular indexed color set timed, I get an "Internal error". There is another indexed colorset within my Petri-net model that is timed and works correctly. I am not sure how I can troubleshoot since I don't understand the error message. Could you help me interpret the error message or give me some hints on what I could be doing wrong?
The model is:
http://imgur.com/JUjPRHK
The declarations of the model are:
http://imgur.com/DvvpyvH
The error message is:
Internal error: Compile error when generating code. Caught error.../compiler/TopLevel/interact/evalloop.sml:296.17-296.20../compiler/TopLevel/interact/evalloop.sml:44.55../compiler/TopLevel/interact/evalloop.sml:66.19-66.27
structure CPN`TransitionID1413873858 = struct ... end (* see simulator debug info for full code *)
simglue.sml:884.12-884.43
"
Thank you~
I know this is an old question, but I run in the same problem and wasted too much time on this, so maybe it will help someone else in the future.
I didn't understand exactly the reason for this, but it seems the problem appears when you play with time values on an arch that ends to a transition (I was updating an integer value to the current time, using IntInf.toInt(time())). Now, if I move the code on the outgoing arch of that transition (that is: the one that ends in a place) there is no error.
I want to program a daemon-manager that takes care that all daemons are running, like so (simplified pseudocode):
void watchMe(filename)
{
while (true)
{
system(filename); //freezes as long as filename runs
//oh, filename must be crashed. Nevermind, will be restarted
}
}
int main()
{
_beginThread(watchMe, "foo.exe");
_beginThread(watchMe, "bar.exe");
}
This part is already working - but now I am facing the problem that when an observed application - say foo.exe - crashes, the corresponding system-call freezes until I confirm this beautiful message box:
This makes the daemon useless.
What I think might be a solution is to make the main() of the observed programs (which I control) "uncrashable" so they are shutting down gracefully without showing this ugly message box.
Like so:
try
{
char *p = NULL;
*p = 123; //nice null pointer exception
}
catch (...)
{
cout << "Caught Exception. Terminating gracefully" << endl;
return 0;
}
But this doesn't work as it still produces this error message:
("Untreated exception ... Write access violation ...")
I've tried SetUnhandledExceptionFilter and all other stuff, but without effect.
Any help would be highly appreciated.
Greets
This seems more like a SEH exception than a C++ exception, and needs to be handled differently, try the following code:
__try
{
char *p = NULL;
*p = 123; //nice null pointer exception
}
__except(GetExceptionCode() == EXCEPTION_ACCESS_VIOLATION ?
EXCEPTION_EXECUTE_HANDLER : EXCEPTION_CONTINUE_SEARCH)
{
cout << "Caught Exception. Terminating gracefully" << endl;
return 0;
}
But thats a remedy and not a cure, you might have better luck running the processes within a sandbox.
You can change the /EHsc to /EHa flag in your compiler command line (Properties/ C/C++ / Code Generation/ Enable C++ exceptions).
See this for a similar question on SO.
You can run the watched process a-synchronously, and use kernel objects to communicate with it. For instance, you can:
Create a named event.
Start the target process.
Wait on the created event
In the target process, when the crash is encountered, open the named event, and set it.
This way, your monitor will continue to run as soon as the crash is encountered in the watched process, even if the watched process has not ended yet.
BTW, you might be able to control the appearance of the first error message using drwtsn32 (or whatever is used in Win7), and I'm not sure, but the second error message might only appear in debug builds. Building in release mode might make it easier for you, though the most important thing, IMHO, is solving the cause of the crashes in the first place - which will be easier in debug builds.
I did this a long time ago (in the 90s, on NT4). I don't expect the principles to have changed.
The basic approach is once you have started the process to inject a DLL that duplicates the functionality of UnhandledExceptionFilter() from KERNEL32.DLL. Rummaging around my old code, I see that I patched GetProcAddress, LoadLibraryA, LoadLibraryW, LoadLibraryExA, LoadLibraryExW and UnhandledExceptionFilter.
The hooking of the LoadLibrary* functions dealt with making sure the patching was present for all modules. The revised GetProcAddress had provide addresses of the patched versions of the functions rather than the KERNEL32.DLL versions.
And, of course, the UnhandledExceptionFilter() replacement does what you want. For example, start a just in time debugger to take a process dump (core dumps are implemented in user mode on NT and successors) and then kill the process.
My implementation had the patched functions implemented with __declspec(naked), and dealt with all the registered by hand because the compiler can destroy the contents of some registers that callers from assembly might not expect to be destroyed.
Of course there was a bunch more detail, but that is the essential outline.
I am having a strange problem in my code. I have many asserts scattered around the code and all have been working fine. Whenever an assert failed I got a message giving me line number of where the failure happened.
Today I wrote another assert in a function which loads a file. Just wanted to make sure that the fie existed. A very simple assert. Here is the relevant code:
//Check that the file exists and can be opened
FILE* f = fopen(filename, "rb");
#ifdef ASSERTIONS_ON
assert(f!=NULL);//#problem For some reason while all other asserts work, this one just crashes the program without reporting line
#else
if(f == NULL)
return MODEL_LOAD_FILENOTFOUND;
#endif
fclose(f);
I know that this does not help a lot but just wanted to showcase what my problem is. My OS is Windows 7. The compiler is GCC. The error message I get from Windows is the usual runtime error but without line reporting:
"The application has requested the Runtime to terminate it in an unusual way. Please contact the application's support team for more information"
What could be the problem? What can possibly cause an assert failure to just request termination without reporting a line where it happens, while in every other case in the same code it works as intended? Thanks in advance for any assistance!
You most likely have FUBAR'ed the stack somewhere before the assert executes.
I am using OpenCV 1 to do some image processing, and am confused about the cvSetErrMode function (which is part of CxCore).
OpenCV has three error modes.
Leaf: The program is terminated after the error handler is called.
Parent: The program is not terminated, but the error handler is called.
Silent: Similar to Parent mode, but no error handler is called
At the start of my code, I call cvSetErrMode(CV_ErrModeParent) to switch from the default 'leaf' mode to 'parent' mode so my application is not terminated with an exception/assertion pop up.
Unfortunately 'parent' mode doesn't seem to be working. I still get the message dialog pop up, and my application still terminates.
If I call cvSetErrMode(CV_ErrModeSilent) then it actually goes silent, and no longer quits the application or throws up a dialog... but this also means that I dont know that an error has occurred. In this case, I think the mode is being set correctly.
Has anyone else seem this behaviour before and might be able to recommend a solution?
References:
cvSetErrMode function reference
Open CV Error handling mode reference
I am going to answer my own question, because after some fiddling around I have worked out what happens.
When you switch to 'parent' mode instead of leaf mode, there is an error handler that gets called cvGuiBoxReport(). cvGuiBoxReport() is the default error handler. It seems that even in parent mode, cvGuiBoxReport() still terminates your application! Oops.
So, to get around that you can write your own error handler, and redirect the error to be handled and NOT terminate the application.
An example error handler:
int MyErrorHandler(int status, const char* func_name, const char* err_msg, const char* file_name, int line, void*)
{
std::cerr << "Woohoo, my own custom error handler" << std::endl;
return 0;
}
You can set up parent mode and redirect your error with:
cvSetErrMode(CV_ErrModeParent);
cvRedirectError(MyErrorHandler);
In a week of servers crashing from uploading corrupt or empty images to our image processing server, here are some thoughts on how I solved the intricacies of OpenCV's error handling. We are using V2.2 in a C++ server.
The problem arises in cv::imread() and cv::imdecode() when the image to be loaded is corrupt (or empty). Normally OpenCV just exits the process with with some error messages, not a good idea when you're running a server which should work all the time.
Reviewing the source code at https://code.ros.org/trac/opencv/browser/trunk/opencv/modules/core/include/opencv2/core/core.hpp I ignored the hint in the source comments for cv::setBreakOnError() and discovered the that following pattern works:
cv::setBreakOnError(true); // Can be set globally
...
...
cv::Mat srcImage = cv::imread(filename, 1);
if (!srcImage.data) throw std::exception("bad image");
cv::imread() will now not exit the process, but passes control to your own exception handling, so you can do with it what you like.
Finding this has saved a lot of heartbreak.