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Re: Strange behavior of Point in watches [message #22891 is a reply to message #22890]

Tue, 25 August 2009 10:07

mirek
Messages: 14266
Registered: November 2005

Ultimate Member

dolik.rce wrote on Tue, 25 August 2009 03:42

Hello,
I've encountered strange problem while debugging my code... Here is simplest possible testcase:

#include <CtrlLib/CtrlLib.h>
using namespace Upp;

class win : public TopWindow{
public:
	typedef win CLASSNAME;
	virtual void LeftDown(Point p,dword flags){
		DUMP(p);
	}
};

GUI_APP_MAIN{
	win().Run();
}

I setup breakpoint in LeftDown() and run in debug mode. When the execution stops at the breakpoint, opening Quick watch window and entering "p" yields:

{
  <Upp::Moveable<Upp::Point_<int>, Upp::EmptyClass>> = {
    <Upp::EmptyClass> = {<No data fields>}, <No data fields>}, 
  members of Upp::Point_<int>: 
  x = -1078378568, 
  y = 8388608
}

Same values are shown if I add watch in the bottom panel of theide. But the most interesting (or puzzling) thing is, that the output in log file is correct, i.e. something like "p = [59, 138]".

At first, I thought that it is a problem in watches, but for something like "Point P(10,20);" watches show correct result. It can be very confusing, I was looking for bug almost an hour on absolutely wrong place, because of this...

Just in case this is compiler/platform specific: I use gcc 4.3 on ubuntu.

Regards,
Honza

PS: I'm not sure if this belongs here. If not, feel free to move this topic to some better place.

It is because correct stack frame for the function is not yet established - gdb reads incorrect values.

If you step inside, you they get corrected.

This is dbg feature, there is nothing we can do about it...

Mirek

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