Potential memory leak?

Qian Xu qian.xu at funkwerk-itk.com
Fri Nov 27 00:59:26 PST 2009


Hi All,

I am using QtD to do some gui stuff. As the QtD documentation described, Qt-
data types should be declared with keyword "scope", so that all variables 
can be deallocated in a right order.

I found a memory leak problem accidentally, when I executed the following 
code very frequently:

// public QRegion united(QRegion region) {...}
 
  scope regionA = new QRegion;
  scope regionB = regionA.united(anotherRegion); // Good Example
  scope regionA = regionA.united(anotherRegion); // Bad Example

I create a variable regionA and unite it with another region. The result of 
the function united is assigned to variable regionB. Everything is fine.

The third line sounds be correct as well. A new instance will be created and 
then the variable regionA will be assigned to this new instance, the old 
instance will be deallocated as soon as the code exits its scope. 

However the old instance, where the variable regionA previously was pointed 
to, still exists. 

I cannot reproceduce this problem with simple D data types.
But do you think this is a bug of dmd 1.051?

Qian Xu




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