Add simple xdf loader executable

[tstenner]

This adds a short example that loads an xdf file and prints some statistics.

[Yida-Lin]

OK, something really weird; both methods load the file, but one gives a weird invalid length thing. I am not sure how to explain this. Both using Qt 5.9.9 MinGW 5.3 Debug.

[tstenner]

I think the end of file isn't handled properly, so the last read might return garbage data

[Yida-Lin]

The funny thing is, even if I just declare an uint_64 variable but without using it, SigViewer loads the file fine. Not so when I remove this line.

[tstenner]

I'm guessing there's something funky going on somewhere else and the additional 8 bytes on the stack shift the problem to somewhere else where it's not noticeable in your test right away.
Valgrind might help, but if you sent me a stacktrace where sigviewer hangs I might have an idea where the problem is.

[Yida-Lin]

I am not so sure how to get the stacktrace, since it hangs instead of breaks on a specific line (well, technically I possibly could, if I really step over one line at a time until it hangs... but not sure I have enough time for that).

Also, if we want to keep this test program long term, maybe better putting it under some subfolder specifically dedicated to testing and add as a sub-project? Currently I don't think it directly "builds" with the project file in Qt Creator since it builds as a library.

[tstenner]

I am not so sure how to get the stacktrace, since it hangs instead of breaks on a specific line (well, technically I possibly could, if I really step over one line at a time until it hangs...

You could also pause the program execution when it hangs. It's not as useful as breaking where something fails, but it still tells you which parts of the program were reached and which not.

[Yida-Lin]

Good to know! Didn't pay enough attention to the pause button before. Here is a screenshot after I click "pause" (when it hangs).