Can anybody explain below statment ?

Christian Ehrlicher

@Qt-embedded-developer said in Can anybody explain below statment ?:

can anybody tell what may be the cause of crash ?

You did something wrong.
Use a debugger, fix your code.

Qt embedded developer

dear yes i knew some thing is wrong. but its auto start application and randomly crash after 10 to 12 hour.

and to figure out i used GDB so it can tell what went wrong and its given me :

                                                                                               Thread 1 "QTApp" received signal SIGSEGV, Segmentation fault.
                  StatusController::slotPollingRequested (this=0x555555ea8440) at ../../QTApp/QTAppComponents/controllers/statuscontroller.cpp:781

781 ../../QTApp/QTAppComponents/controllers/statuscontroller.cpp: No such file or directory.

and its part of code is below :

                 if (lConnProbe->getProbeSts() != PROBEDISCONNECTED)
                    {
                        if(lConnProbe->getProbePerso() == "Arterial")
                        {
                            bACuvetteNotDetected = false;
                            list<int>::iterator errorcode;
                            for (errorcode = lConnProbe->getProbeErrorList()->begin(); errorcode != lConnProbe->getProbeErrorList()->end(); ++errorcode)
                            {
                                switch(*errorcode)
                                {
                                case EC_HSAT_COLOR_CHIP_FAILURE:
                                {
                                    TechnicalAlarmModelData lAlarm1;
                                    lAlarm1.aAlarmType = EnumClass::EnTechAlarmType::TECHALARM_INFO;
                                    lAlarm1.aAlarmString = "Arterial H/S-" + QString::fromStdString(lConnProbe->getSerialNumber()) + " Color Chip test failure <H151>";
                                    lAlarm1.aActionText = "Check surfaces of color chip and H/S and clean if necessary.\n\nIf error persists, use replacement H/S if available\n Technical Support";
                                    lModelDataList.push_back(lAlarm1);
                                }
                                break;

Christian Ehrlicher

I will not debug your code - provide a minimal, compilable example or use code checker or other tools like asan.
And why do you ask the same question you already did 17 hours ago?

https://forum.qt.io/topic/144226/what-is-the-reason-behind-below-crash-of-qt-application

Qt embedded developer

Dear @Christian-Ehrlicher Because i want to understand from back trace that what i done wrong. because nobody told me from back trace that what went wrong.

Because if i use asan or gdb. may they give same reason like above reason.

So if anybody explain above back trace it can help me.

This question is all about when this type of trace log get generated ? what it mean to say ? And thanks i removed that sub question becuase i want to do discussion of it in this post.

i have seen that there are lots of post available for similar type of trace.

So if any expert can help me when this happen it will redirect to right thing.

JonB

@Qt-embedded-developer
I don't think anyone can say what precisely is wrong from that backtrace. All the more so since it takes a long time to show up, so it's some particular situation.

@Qt-embedded-developer said in Can anybody explain below statment ?:

781 ../../QTApp/QTAppComponents/controllers/statuscontroller.cpp: No such file or directory.
and its part of code is below :

And which of those lines is #781?? You know, we do not.

Qt embedded developer

@JonB

781 line may be

below line

if (lConnProbe->getProbeSts() != PROBEDISCONNECTED)

or

switch(*errorcode)

this block of code also i mentioned above.

Axel Spoerl

@Qt-embedded-developer
A lot of posts about segmentation faults don’t mean that they all have the same reason. The error just means that unallocated memory is accessed. And without showing us a reproducible code example, we can only guess.

So let’s guess.

Your trace doesn’t look like you access a stale object or an invalid pointer. Yet, that can’t be completely excluded. You explain that you show data in a graph and it crashes after 15 hours. You don’t mention that you manage memory usage, e.g. you store only what is displayed and free what is not.
So the guess is that the application keeps consuming memory until the system runs out of it. Then the stack flows over and it accesses an unallocated memory page. Boom. Segfault at a completely random place.

JonB

@Qt-embedded-developer
As @Axel-Spoerl has just written. Meanwhile your if (lConnProbe->getProbeSts() != PROBEDISCONNECTED) and switch(*errorcode) are about 10 lines apart, so you should be able to locate line #781 a bit better than that. Though if you are in @Axel-Spoerl's "short of memory" case it won't help much, but still...

Qt embedded developer

@JonB @Axel-Spoerl

mean while i figure out from both which line is it.

Can anybody tell me.

IF my app need to store data of 15 hour and show immediately on qcustomplot ?

then what need to be the approach to deal with sort of memory?

because i have doubt that my data get stored into ram.

JonB

@Qt-embedded-developer
If you stuck to one question about this it would help. In your other thread
@Pl45m4 said in What is the reason behind below crash of QT application ?:

But there is no point to store all 15h of data at any time in your graph. Work with models and only show the visible area of your graph. Use downsampling to reduce the datapoints, when you show the whole timespan.

Qt embedded developer

@JonB means the immediate data which i need to show on qcustomplot based graph.

need to get store into local file and when user click on graph button and want to see variation into graph at time i need to load that onto qcustom plot.

my data is coming every one second. and data i need to show in three format 2min , 2 hr and 20hr

so i need to load according to that.

means when 2 minute interval data i am showing at that time no need to do down sampling but when show 2 hr or 20 hr data at that time need to do down sampling.

though there is doubt that when i load 20 hr data into ram and show at that time also this issue may come ?

JonB

@Qt-embedded-developer said in Can anybody explain below statment ?:

means when 2 minute interval data i am showing at that time no need to do down sampling but when show 2 hr or 20 hr data at that time need to do down sampling

So go ahead and do that! 20 hours of data every one second is 72,000 points, which is quite a lot for the user to look at.

In any case first look to see whether when it crashes after 20 hours, or after loading that data into memory, you are or are not anywhere near running out of free memory.

Qt embedded developer

@JonB Sorry i forgot to mention that i am showing 96
sensor data,

means that data is 72000 * 96.

i am showing multi graph. so at a time need is 4 sensor data.

so it is 72000 * 4.

And our crash line is

switch(*errorcode)