Qt debugger is taking its own initial values
Hello guys, :-)
I’m writing a simple function for merge sorting. Of course everyone will tell me “use std algorithm sorters”, but I can’t do that because the container, in which is that data I wanna sort, is somehow a very complicated linked list and I can’t do it with std containers. I’m gonna finish this sorter and do my minor changes to fit in my container.
The problem is the following: I’m debugging the function of sorting step by step. The program starts with initial conditions for the variables i, j and k. But Qt debugger sometimes give random values for i, although it’s initialised. It’s driving me crazy, and I can’t understand why that’s happenening. Any clue? please find the code below:
- template <typename T>
- void sort(vector<T> &data)
- {
- vector<T> tempData = data;
- unsigned long int currentPower = 1;
- unsigned long int i, j, k;
- i = 0;
- while(currentPower < data.size())
- {
- while (i < data.size())
- {
- j = 0;
- k = 0;
- while(j < currentPower || k < currentPower) //here I start my first breakpoint for debugging, where i isn't 0 sometimes.
- {
- ...
- }
- i += 2*currentPower;
- }
- currentPower *= 2;
- }
- data = tempData;
- }
Any ideas? I always have to start the program like 10 times to get i to be initialised as 0.
Thanks for any efforts :-)
14 replies
I’ve done that. The debugger is sometimes skipping some lines… I tried setting a breakpoint at the very first line
- vector<T> tempData = data;
and it some times skips it!!!!! I don’t understand what’s going on!!! it’s acting crazy!
Is there someway (that I don’t know of) to start debugging from the middle? perhaps I’m doing that without knowing it!!!!
Are you sure that the code matches the binary? If the debugger skips lines, halts on strange locations and shows odd values you most probably looking at a different version of the source than the one which was used to compile the current binary.
Try to recompile your project with the sources you are actually using to debug the binary.
Here’s the build log for a debug version:
——————————————————————————————————-
17:54:15: Running build steps for project MergeSort…
17:54:15: Configuration unchanged, skipping qmake step.
17:54:16: Starting: “D:\QtSDK\mingw\bin\mingw32-make.exe”
D:/QtSDK/mingw/bin/mingw32-make.exe -f Makefile.Debug
mingw32-make.exe1: Entering directory `C:/Users/Sam/Dropbox/common_src/MergeSort/MergeSort-build-desktop-Qt_4_8_0_for_Desktop_-_MinGW__Qt_SDK__Debug’
g++ -c -g -frtti -fexceptions -mthreads -Wall -DUNICODE -DQT_LARGEFILE_SUPPORT -DQT_DLL -DQT_CORE_LIB -DQT_HAVE_MMX -DQT_HAVE_3DNOW -DQT_HAVE_SSE -DQT_HAVE_MMXEXT -DQT_HAVE_SSE2 -DQT_THREAD_SUPPORT -I“d:\QtSDK\Desktop\Qt\4.8.0\mingw\include\QtCore” -I“d:\QtSDK\Desktop\Qt\4.8.0\mingw\include” -I“d:\QtSDK\Desktop\Qt\4.8.0\mingw\include\ActiveQt” -I“debug” -I”..\MergeSort” -I”.” -I“d:\QtSDK\Desktop\Qt\4.8.0\mingw\mkspecs\win32-g++” -o debug\main.o ..\MergeSort\main.cpp
..\MergeSort\main.cpp: In function ‘int main(int, char**)’:
..\MergeSort\main.cpp:143: warning: comparison between signed and unsigned integer expressions
..\MergeSort\main.cpp: In function ‘void sort(std::vector<T, std::allocator<_CharT> >&) [with T = double]’:
..\MergeSort\main.cpp:147: instantiated from here
..\MergeSort\main.cpp:28: warning: comparison between signed and unsigned integer expressions
..\MergeSort\main.cpp:32: warning: comparison between signed and unsigned integer expressions
..\MergeSort\main.cpp:147: instantiated from here
..\MergeSort\main.cpp:103: warning: unused variable ‘xxx’
g++ -Wl,-subsystem,console -mthreads -o debug\MergeSort.exe debug/main.o -L“d:\QtSDK\Desktop\Qt\4.8.0\mingw\lib” -lQtCored4
mingw32-make.exe1: Leaving directory `C:/Users/Sam/Dropbox/common_src/MergeSort/MergeSort-build-desktop-Qt_4_8_0_for_Desktop_-_MinGW__Qt_SDK__Debug’
17:54:19: The process “D:\QtSDK\mingw\bin\mingw32-make.exe” exited normally.
——————————————————————————————————
The part “…” has only some other while loops and break commands. No goto or return commands.
I don’t have a problem now, since I finished writing the sort function I wanted to write. But the problem persists and still there, and in the future it will happen again.
The problem is that the debugger “resumes” debugging after stopping it, and not starting from the beginning. I don’t know how to disable this stupid feature. If anyone knows, please say, because this summarises the problem.
Please start a console program with your Qt and try to debug stuff similar to my code, and you’ll see how it “resumes” debugging. I’m using Qt SDK 1.2.
Bug reported:
https://bugreports.qt-project.org/browse/QTBUG-24388
Thanks for the help guys. Hopefully they’ll solve it soon :-)
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