Basic questions to debugging

[emigrand]

Since no human is going to keep up with 1000+ samples/second anyway, you should consider capturing the data every cycle but only redrawing the plot every 500 samples or the like.

I implemented something similar already, so replotting efforts are minimized, problem vanished!

To debug your code using Qwt components does not require a debug Qwt:

This is what I want to do. Writing my own program using Qwt classes. Then I want to debug the whole thing.

to debug Qwt code does.

Where is the difference? Or would this mean debugging the Qwt libraries and stuff?? I wouldn't dare, should I? So according to my goal outlined above, I still assume that I don't need to make a debug vesion of Qwt in order to be able to debug code that uses Qwt classes. But: If I do so, I get the error messages already mentioned:

:: error: cannot find -lqwtd
:: error: collect2: ld returned 1 exit status

Your build of the debug Qwt looks OK

Which build? I just asked if this is the way I would have to build it. But if I don't need to...(see above). But maybe I got this whole thing wrong again and I am supposed to build the debug version, otherwise I will not get rid of the errors??

I really would like to add these lines to my .pro file, because it looks clear and obvious:

CONFIG(release, debug|release) {
  message(Release build!)
  LIBS+=-Lc:/qwt-6.0.1/bin -lqwt
...
}
CONFIG(debug, debug|release) {
  message(Debug build!)
  LIBS+=-Lc:/qwt-6.0.1/bin -lqwtd
...
}

CONFIG(release, debug|release) {
  message(Release build!)
  LIBS+=-Lc:/qwt-6.0.1/bin -lqwt
...
}
CONFIG(debug, debug|release) {
  message(Debug build!)
  LIBS+=-Lc:/qwt-6.0.1/bin -lqwtd
...
}

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But I don't have a /bin-folder!!! Should this observation tell me something? Does it tell you something about my installation or mental condition?

I hope for the first...
Thank you Chris for your patience so far...

[ChrisW67]

If you need to single step through your code code then your code must be built with debug symbols. As you step through your code and it enters Qwt functions in the library you will either:

• See a low level disassembly of the release mode Qwt library routine, or
• A high level source code view of the debug mode Qwt library routine. (The source is embedded in the library to enable this.)

It seems unlikely that you want/need to debug the Qwt code. You can Step Over the Qwt calls to avoid the disassembly.

I am not intimately familiar with Windows Qwt builds. I assumed that the debug mode Qwt library would follow the same convention as the Qt libraries; appending a 'd' so that release and debug can exist side-by-side. If the debug library gets the same name, i.e. qwt.dll, then you are better off building release mode and installing into Path A, and debug mode installed into Path B and adjust INCLUDEPATH and LIBS accordingly.

I also assumed a directory structure. You will have to adjust paths to suit what has actually happened on your machine.