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Int assigning problem

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mcco1

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Int assigning problem

Aug 19th, 2009

I have this piece of code

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 C++ Syntax (Toggle Plain Text) 
// some function
int px;
void SomeFunction( void *dummy )
{
	...
 
	RECT rect;
	GetWindowRect(hWnd, &rect);
	px = ((rect.right - rect.left) / 2) - 60;
 
	...
 
	// Terminate thread
	_endthread();
}
// some function
int px;
void SomeFunction( void *dummy )
{
	...

	RECT rect;
	GetWindowRect(hWnd, &rect);
	px = ((rect.right - rect.left) / 2) - 60;

	...

	// Terminate thread
	_endthread();
}

And my problem is px doesn't get assigned.. it stays 0.. although in the debugger I can see all the values inside rect..
please help me

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Re: Int assigning problem

Aug 19th, 2009

What are the values of RECT members?

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mcco1

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Re: Int assigning problem

Aug 19th, 2009

•

Originally Posted by Laiq Ahmed

What are the values of RECT members?

http://msdn.microsoft.com/en-us/libr...97(VS.85).aspx

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typedef struct _RECT {
  LONG left;
  LONG top;
  LONG right;
  LONG bottom;
}RECT, *PRECT;
typedef struct _RECT {
  LONG left;
  LONG top;
  LONG right;
  LONG bottom;
}RECT, *PRECT;

The values are numbers

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Re: Int assigning problem

Aug 19th, 2009

Thank you mcco for providing me the definition of RECT structure

kindly provide me the values (numbers), It seems that your expression evaluates to zero thats why I've asked to provide me the values not the RECT members.

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Re: Int assigning problem

Aug 19th, 2009

•

Originally Posted by mcco1

I have this piece of code
Help with Code Tags

C++ Syntax (Toggle Plain Text)
// some function
int px;
void SomeFunction( void *dummy )
{
	...
 
	RECT rect;
	GetWindowRect(hWnd, &rect);
	px = ((rect.right - rect.left) / 2) - 60;
 
	...
 
	// Terminate thread
	_endthread();
}
// some function int px; void SomeFunction( void *dummy ) { ... RECT rect; GetWindowRect(hWnd, &rect); px = ((rect.right - rect.left) / 2) - 60; ... // Terminate thread _endthread(); }
And my problem is px doesn't get assigned.. it stays 0.. although in the debugger I can see all the values inside rect..
please help me

What about if you change px from int to long? Does that give you any differemt results?
The thing to take note of here is that px is currently declared as an int. Whereas rect.right and rect.left are both LONG/long variables.

Therefore if the result of your calculation is less than 1.0 (e.g. something like 0.43455664), then because px is an int, the calculated value will be truncated to 0.
Whereas if you alter px to be long, you'll get the actual calculated value (in my example 0.4345564).

I could be wrong, but that looks like the most obvious explanation to me!

oh, hang on.....Looking at that code, another thing strikes me as odd....
px is declared outside of the function, but used inside it..
That's probably your problem right there!
The px used in the function and the px outside of the function might not be the same variable, they might have different scope.
If you could post some more code, we might be able to determine whether or not this is the case!

Cheers for now,
Jas.

Last edited by JasonHippy; Aug 19th, 2009 at 11:33 am.

There are 10 types of people in this world.....
Those who understand binary .....
And those who don't!

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MrSpigot

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Re: Int assigning problem

Aug 19th, 2009

•

Originally Posted by JasonHippy

What about if you change px from int to long? Does that give you any differemt results?
The thing to take note of here is that px is currently declared as an int. Whereas rect.right and rect.left are both LONG/long variables.

Therefore if the result of your calculation is less than 1.0 (e.g. something like 0.43455664), then because px is an int, the calculated value will be truncated to 0.
Whereas if you alter px to be long, you'll get the actual calculated value (in my example 0.4345564).

A 'long' variable in this context is still an integer, not a float, so changing px to long will make no difference.
The most likely explanation, as you suggested, is that px has also been declared locally and the OP is examining the global variable.

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Re: Int assigning problem

Aug 19th, 2009

Try
::px = ((rect.right - rect.left) / 2) - 60;

I am assuming there is a local variable hiding the global.

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Re: Int assigning problem

Aug 19th, 2009

Check out if you have declared a variable inside SomeFunction with the same name as px, in this case the local variable is used and the global variable is cached.

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Re: Int assigning problem

Aug 19th, 2009

Sorry the global variable is hidden not cached

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mcco1

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Re: Int assigning problem

#10

Aug 19th, 2009

•

Originally Posted by JasonHippy

oh, hang on.....Looking at that code, another thing strikes me as odd....
px is declared outside of the function, but used inside it..
That's probably your problem right there!
The px used in the function and the px outside of the function might not be the same variable, they might have different scope.
If you could post some more code, we might be able to determine whether or not this is the case!

Cheers for now,
Jas.

Thanks! that was my problem!
this function is pretty long and I forgot that I have another px in it.