Avoiding memory leaks during transfer of ownership

Article Metadata

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Compatibility

Platform(s): S60

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Article

Created: User:Technical writer 1 (26 Nov 2007)

Last edited: hamishwillee (15 Jun 2012)

Description

The following code demonstrates a common pattern for creating memory leaks:

 User::LeaveIfError(bar.TakesOwnershipIfSuccessful(CFoo::NewL()));

If the construction of CFoo succeeds, but then the function call that is supposed to take ownership of it fails, then the newly-created CFoo instance is orphaned.

Solution

The only way to do this safely is to use the cleanup stack:

 CFoo* foo = CFoo::NewL();
 CleanupStack::PushL(foo);
 User::LeaveIfError(bar.TakesOwnershipIfSuccessful(foo));
 CleanupStack::Pop(foo);

The most common situations where these kind of leaks occur are array operations such as Append() or Insert().