I am new to OCaml which I installed via opam. My compiler is dune. Each time I build my project and run it, it crashes but I get no information from where it crashes in the code.
A friend of mine who is doing the same thing get information about the line where it crashes.
If anyone have an idea it will be incredible !
Best regards,
You could add the following in you main, which turns on the recording of exception backtraces:
let main =
record_backtrace true;
...
Alternativelly, you can set the b flag through the OCAMLRUNPARAM variable.
you can try using try\catch, exceptions and printing to find where the problem is at.
in case the exception is something you have raised, you can try to replace it with a costume exception to get the various details.
exception Yourexception of string;;
raise (Yourexception "the problem is here") ;;
if the problem is an OS exception, such as stack overflow, you can try placing prints all over the place, and slowly pinpoint the exact location
print_string( "1\n");
and when all else fail, use try and catch to slowly pinpoint the location (you can google the exception to help pinpoint the cause. for example finding that list raise the exception or something)
try (-your code-)
with exception -> (- print or handle or whatever - );;
these steps help with most of the languages, so its nice to remember them
Related
I'm trying to write vtkImageData as a DICOM. I keep getting an "Access Reading Violation" when I try to write the image.
Unhandled exception at 0x00007FFDA30ECA50 : 0xC0000005: Access violation reading location 0x000001BD38D5C000
Here is my code:
vtkSmartPointer<vtkDICOMWriter> dcmWriter = vtkSmartPointer<vtkDICOMWriter>::New();
dcmWriter->SetInputData(testDat);
dcmWriter->SetFileName(fullPath.toStdString().c_str());
dcmWriter->Update(); // this line breaks
dcmWriter->Write();
testDat is a vtkSmartPointer<vtkImageData> type and has data in it. Any thoughts on whats causing the error? I can't find anything similar online.
I followed this example: https://github.com/dgobbi/vtk-dicom/blob/master/Examples/TestDICOMWriter.cxx
I don't have metadata, but that shouldn't be a problem.
I need to make some guesses here because you didn't post all of your code, but I suspect that the problem happens in the following line:
dcmWriter->SetFileName(fullPath.toStdString().c_str());
toStdString() is most probably returning a temporary std::string (fullPath looks like a Qt QString), on which you call c_str(). After the statement, your temporary is destroyed and whatever you have passed to SetFileName is now a dangling pointer. Hence the segfault.
Try the following instead::
const auto pathString = fullPath.toStdString();
dcmWriter->SetFileName(pathString.c_str());
This should hopefully work fine. Even if not, it definitely is an issue with your code.
These lines are from the example you posted:
writer->SetFilePrefix("/tmp");
writer->SetFilePattern("%s/IM-0001-%04.4d.dcm");
and you use
dcmWriter->SetFileName(fullPath.toStdString().c_str());
It seems that vtkDICOMWriter writes several files so you probably need to provide a file pattern. Anyway, it's hard to guess why it gives a reading error and it's hard to help if you don't post a full working example.
Last, vtkDICOMWriter is not a class from vtk, it was released separetely (it seems) in 2017. This means it's not tested against the rest of VTK at every new release.
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.
There is something strange happening when I try to debug application. Simply the debugger does not stop on breakpoints when I set breakpoints in catch portion of try-catch block.
Here is an example.
try {
throw std::overflow_error("test");
} catch (...) {
qDebug() << "caught"; // HERE, I SET BREAKPOINT ON THIS LINE
}
It prints the "caught" on screen when exception occurs but it does not stop on this line. (If you ever wonder; Yes, I'm building app in Debug mode and running in Debug mode)
Am I suffering from lack of fundamental knowledge about how gdb works? (I mean maybe it does not stop because breakpoints in catch portion does not work)
Any help would be greatly appreciated.
Thanks.
To catch an exception in IDE, you need issue gdb commands directly in gdb console.
Here's link how to get into gdb console in Qt Create IDE:
Accessing gdb console in Qt-Creator
Once you're the type
catch throw
to stop when your program throws an exception or
catch catch
to stop in the catch block.
If you need to catch a specific library exception, read this thread: GDB: How to break when a specific exception type is thrown?
for people using LLDB,
# set on both throw and catch
breakpoint set -E C++ -h true
# or on catch
b __cxa_begin_catch
# or on throw
b __cxa_throw
while will set breakpoints on throw and catch.
#ben sen, I guess any opinization may result in such a behavior. There are many ways how those options can be specified (via environment variables aka CFLAGS or via IDE options to the project), but they all result to some particular -O option given to the compiller command line. Even if nothing is given at all, please check what is the default optimization for your compiller. My proposal would be to explicitely give -O0 to the compiller and check that no other -O options are supplied.
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.
im having issues with MySQL++ and desperately need help.
I'm using Visual Studio 2010, MySQL++ v3.1.0 and MySQL v5.1.59( x86 & x64 );
All Library's have been compiled correctly. This error only occurs in Debug version due to the compiler setting "Both (/RTC1, equiv. to /RTCsu) (/RTC1)" being on.
Edit: I should note that this only happens in Debug version. In Release it works like a charm
I've tracked the problem back to the mysqlpp_d.dll, the MySQL++ object are crashing on there destructors due to reference counting. It complains about not being capable of accessing the memory of the ref counter, and when it tries to decrease it, it crashes. At least thats what I think happens.
I tried this to make sure everything gets derefrenced and removed in the correct order (even tho its irrelevant, but helped me track the true problem down I hope): http://pastebin.com/Ru0uYcy9
It crashes with:
First-chance exception at 0x000007feeef5dd4c (mysqlpp_d.dll) in Launcher.exe: 0xC0000005: Access violation writing location 0x000007feeeff5148.
Unhandled exception at 0x000007feeef5dd4c (mysqlpp_d.dll) in Launcher.exe: 0xC0000005: Access violation writing location 0x000007feeeff5148.
And breakes here:
http://pastebin.com/9Mfr7NwB
This code has a serious bug:
mysqlpp::UseQueryResult res;
{
mysqlpp::Query query = conn.query();
query << "SELECT USER();";
res = query.use();
row = res.fetch_row();
}
You aren't consuming all the result sets. In MySQL, stored procedures that return data return at least two separate result sets: the first is the results you asked for, and the second is status information about the call itself. See examples/multiquery.cpp in the MySQL++ source distribution for the correct way to handle this. Also see section 3.16 in the MySQL++ user manual.
The main consequence of this is that later queries on the same connection will fail.
I think your memory corruption is actually a secondary effect, and that the primary problem stems from ignoring the MySQL C API's attempts to tell you that you're trying to run two overlapping queries on the same connection, because you didn't consume the entire first result set. From what little code you've posted, I can see that you're ignoring returned error codes, so if you've also disabled MySQL++ exceptions, your code will completely ignore this error and blithely go on to stomp all over things it shouldn't.
By the way, please lose the trailing semicolon on the query. It isn't needed with the C API, and can cause confusion, especially in the face of multi-queries. Use semicolons only to separate multiple statements in a single query.