I am using Qt Creator to develop a C++ application, and I am trying to track down some memory leaks.
I have followed these instructions*, and have Valgrind isntalled on my Ubuntu machine.
I begin my application from the Analyze Memory section, and after clicking the stop button I am told that Tool Analyze Memory finished, 928 issues found. However, no results appear in the analysis section, which remains blank.
Am I doing something wrong? Where can I find the results of the memory analysis?
*Confusingly, the instructions ask for a 'release' build configuration, but selecting this causes a warning in Qt saying that the memory analysis tool requires a debug configuration. I have tried both ways round.
I've checked it in my Qt Creator and it works. I'm using version 2.3.1 with Qt 4.7.4 and Valgrind 3.7.0. I've tested it on dropsite example with Debug build configuration. I've also tested it with my CMake based project (compiled with -g and -O0 flags) and it also worked. Make sure, that next to start button Valgrind Memory Analyzer is chosen. On the same bar you'll find arrow icons. Next to them is icon of funnel (I think). Click it and make sure that types of errors you're interested in are checked.
If it won't work, and you don't want to use Valgrind tools from console, there are other Valgrind GUIs like Valkyrie.
EDIT: I've updated Qt Creator to version 2.4.0rc1 and checked it with my CMake project. It also showed no results, while reporting few hundred issues. Solution to this was checking External errors after clicking funnel icon.
EDIT2: In final 2.4.0 issue was fixed.
You did nothing wrong. In the Valgrind menu, press the Filter icon and select External Errors. You will see all issues appearing. Those are most likely not from your application, but Qt- or else-related, so you can often ignore them.
X issues found refers to the total number of issues; when External Errors is unselected, only those related to your app show up. If none appears, Valgrind has not detected any memory leak in your app.
Related
When I run Valgrind memcheck tool from Qt Creator on my unit test project (which is using google test), I have a weird issue with the output. Qt Creator is convenient as it filters out the external errors but with my unit test project it looks like it struggles to parse the valgrind ouput. As an example, at some point in one of my tests I have the following:
QRegularExpression regExp(RegExpGetter::date());
ASSERT_TRUE(regExp.isValid());
EXPECT_FALSE(regExp.match(QStringLiteral("29-02-2021")).hasMatch());
//...
And while some Valgrind output is parsed correctly by Qt Creator, others (such as the output produced by my test above, but also many other tests) are displayed in the console output formatted as xml. Now, I noticed that as soon as this issue arises, the next errors are not parsed correctly but are all displayed in the console (which makes it hard -- and that's an understatement, to detect my own errors). I created some explicit memory leaks and while some in the previously ran test suites are displayed correctly, others are not but I can still find them in the console if I search for them. Here's a screenshot of the issue.
I tried disabling Google Test ouput, thinking it may conflict with how Qt Creator parses the valgrind results, but it didn't help. Any idea how to solve my problem?
I am running valgrind 3.16.1 and Qt Creator 4.14.2 on an Ubuntu virtual machine.
I have recently installed Qt Creator 4.8.0 based on Qt 5.12.0 and I have it configured like in the image below. However, I haven't managed to start the debugger. As it can be seen, the debugger is correctly set for this kit, the one I'm using right now.
Any solution?
Thanks!
Wow! I found it!!! Here in the tab "projects", there are several build and run configurations. Despite you select a default kit, the final one being executed is the one in black under this tab.
Finally I disabled all of them except the one that was properly configured in the Kits window and it worked. I hope this information is helpful for someone. I don't think that part of the configuration is clear.
I got the same error, but in my case I was using the MSVC compiler and the kit didn't manage to find the CDB debugger. I was able to fix it by going to "Add or remove programs" -> "Windows Software Development Kit" -> Modify -> Change -> Debugging Tools for Windows.
In my case it was needed to select "Enable C++" under Debugger settings
screenshot
The same dumm error QT creator shows when you simply don't have gdb installed.
Worked in my case ;)
I had the same error in MacOS, debugger suddenly stopped working (LLDB debugger worked in XCode but not Qt Creator).
In this case, I reinstalled Qt Creator and reinitialized the config by removing the .config/QtProject directory located in homedir. This solved the problem.
I had the same issue when Qt Creator didn't recognized the path to the Debugger. Due to some reason it showed multiple Auto-detected Debuggers at the same location. And on the top one of the list with the red error indicator.
see
Projects->Manage Kits...->Debuggers
I removed the erroneous Debugger and restart the Qt Creator.
my Qt (QML/C++) application crashes and I can not find the reason why. I tried to output a lot of information but some signal/slot connection probably causes a crash. I spent many hours trying to find the reason but I failed.
The only good point is that I can reproduce the crash whenever I want.
Unfortunately I don't know hot to use the included GDB debugger. This is the output I got:
How do I find from this what happened and where? I need to find at least the function, in which my application crashed.
Or what else could I try? Unfortunately I can not disable the signal/slot connections or the associated functions, because then I can not get to the point, where it crashes.
Qt has detailed documentation on how to install a debugger found here: QtCreator Debugger
MingW does have a GDB that can be used to debug the application better. You can also use CDB to debug, just depends on your preference.
Once that is installed, you'll be able to set breakpoints and check variable information to see where your program is crashing using the Debugger view in QtCreator.
Tools->Options->Build & Run
If you have Qt version kit like this you need to check debuggers.
https://i.stack.imgur.com/LaY1p.png
https://i.stack.imgur.com/8kTG6.png
You need to install MinGW and after install you will be have debugger. After install press F5 to start debuging.
I set Qt Creator to break when a C++ exception is thrown:
I then tested it with this code:
try {
throw std::runtime_error("error");
} catch (std::exception &e) {
qDebug("%s", e.what());
}
But it didn't break on throw std::runtime_error("error");. I'm using CDB, not GDB, because I'm using the MSVC Kit.
Edit: There is another question where CDB is working for the OP, even if slowly. So it should work in principle. My configuration is: Qt Creator 3.3.0, compiling with Qt4/MSVC 9.0 (x86), the debugger is CDB 6.2.9200.16384.
Edit 2: This is what I'm getting in the CDB log window (I made a diff between the CDB log with and without the breakpoint):
<bu100400 CxxThrowException
<!qtcreatorcdbext.breakpoints -t 1 -v
<!qtcreatorcdbext.pid -t 2
dATTEMPT SYNC
d*** Bp expression 'CxxThrowException' contains symbols not qualified with module name.
1 breakpoint(s) pending...
*** Unable to resolve unqualified symbol in Bp expression 'CxxThrowException' from module 'C:\Windows\WinSxS\x86_microsoft.windows.common-controls_6595b64144ccf1df_5.82.7601.18201_none_ec80f00e8593ece5\comctl32.dll'.
Full CDB log (in case needed): http://pastebin.com/jhNRy9bE
Edit 3: #HansPassant's explained why it fails in the comments:
Keep in mind that you are using a very old version of MSVC++, big changes at VS2012. The pastebin shows it being out of sync pretty badly, never getting to the DLL that contains __CxxThrowException#8 (MSVCR90D.dll) before the exception is thrown. It is simple with the sxe debugger command, automatic break when any exception is thrown.. Maybe you shouldn't be using QT's UI at all, it looks too gimpy. – Hans Passant 10 hours ago
Just look at the trace, the debugger shows what DLLs it is searching for "CxxThrowException". It never gets to msvcr90d.dll. And the exception is thrown while it is searching for the symbol after which it all ends. Completely out of sync. – Hans Passant 56 mins ago
I'll just write up why this is going wrong, a workaround is going to be difficult to find. The debugger trace in your pastebin tells the tale.
The basic issue is that the communication between the debugger and the QT front-end is rather poor. And in your case it gets out of sync, QT doesn't wait long enough for the debugger to complete the command. QT tries to set a breakpoint on the msvcr90d.dll!__CxxThrowException#8 function, the one that raises a C++ exception in the Microsoft CRT. This function can be present in more than one executable file if the program uses multiple CRTs. A pretty common mishap, caused by building with /MT. And sometimes intentional if you use a well-isolated DLL that you interface with by using COM.
This takes a while as you might imagine, the complaint in the linked question, the debugger has to plow through the symbol information for every DLL that's loaded. It will take especially long if the PDB for the DLL needs to be downloaded from the symbol server and doesn't otherwise get cached so it is available the next time you debug. Not your issue afaict, it does setup the cache location to C:\Users\sasho\AppData\Local\Temp\symbolcache. Go have a look-see to verify that you do see PDBs for the operating system DLLs there.
This operation is tricky, the debugger doesn't give a good signal that it is done searching the DLLs. What the QT should do is verify the debugger feedback against the list of DLLs it obtained. It does not do that, it issues the g command before the debugger is done searching. Could be a timeout that is too short but it actually looks like QT doesn't count on the debugger performing this command in the background. A convenience to a human, not exactly very helpful here :)
There ought to be a way to configure CDB to not perform this search in the background. This is well-hidden, I don't see anything in the debugger.chm help file but it probably wasn't updated in a while. Google doesn't help either. I'd recommend you ask a question about it. Most significantly perhaps is that you have a rather major mismatch in version numbers. The compiler you use is 2008 vintage, the debugger is quite new, SDK 8.0 version, I can't tell what QT version you use.
So a possible workaround is to intentionally use an older version of CDB, one that's more likely to have been tested with the QT front-end version you use. Download the corresponding SDK version, version 6.0 matches the VS2008 time frame. I think the "Debugging Tools for Windows" was still a separate download back then and not yet included in the SDK. Another workaround is to stop relying on the friendly QT front-end and learn to drive CDB from the command prompt. Moderately more useful is WINDBG, uses the same debugging engine but has a GUI interface. Just moderate, it is still mostly prompt driven. You do lose several days of your life learning the commands however. Getting the debugger to break when an exception is thrown is trivial, use the sxe command.
I'm trying to use QT Creator for an open-source project I downloaded from github.
After some fuddling around I managed to get the project to compile in QT Creator and run in debug mode.
However, I have an issue : strangely the breakpoints that I set are only available for that instance for the debug run for QT Creator. When I stop the debugging, and relaunch the debugging, the previously stated breakpoints are still there, but they are no longer valid. (meaning Qt Creator skips over them). I've verified that new breakpoints are still valid - it's the old ones that become invalid even though they are still listed.
I did not even update any code, just added breakpoints, hit debug and the old breakpoints became invalid even though they are still showing.
No sacarsm intended, but is this a "feature"? If so, how do I turn it off?
If not a feature, what can I try?
It's very painful to re-add breakpoints every time I run a debug.
Using Mac OSX 10.9 here, Qt 5.2, with Qt Creator 3.0 for Mac.
Thanks.
EDIT : Some more info. I realised that whenever the breakpoint works, it has a tiny hour glass next to it, like in the picture. What does the hour glass mean? It could just be something dumb that I'm not doing....
in the end I filed a bug with Qt Creator. For those interested pls check here.
https://bugreports.qt-project.org/browse/QTCREATORBUG-11184