CWlanScanInfo leaks memory?

[jpgustaf]

Hi!

I tried the following function with S60 3rd ed. FP1 but it seems like CWlanScanInfo leaks memory the function leaves even if it's added to the cleanup stack.

CWlanScanInfo* scanInfo=CWlanScanInfo::NewL();
CleanupStack::PushL( scanInfo );
if ( someThingHappens ) 
   {
   User::Leave( KErrMyOwnError );
   }
CleanupStack::PopAndDestroy();

Is there something I have done wrong (some additional steps to add CWlanScanInfo into the cleanup stack)?

[wizard_hu_]

Why do you think that there is a leak?

[jpgustaf]

Thanks for your reply.

Why do you think that there is a leak?

My application exits with ALLOC: 260200ba, that seems to disappear if CWlanScanInfo is not created.

The full function looks like this

CDesC8Array* CWlanScanner::AccessPointMacArrayL()
    {
    const TInt KMaxNumberOfAccessPoints( 20 );
    CDesC8Array* accessPoints = 
        new (ELeave) CDesC8ArrayFlat(KMaxNumberOfAccessPoints);
    CleanupStack::PushL( accessPoints );

    CWlanScanInfo* scanInfo=CWlanScanInfo::NewL();	
    CleanupStack::PushL( scanInfo );
    CWlanMgmtClient* client=CWlanMgmtClient::NewL(); // <--- This leaves if WLAN is not supported
    CleanupStack::PushL( client );

    client->GetScanResults(*scanInfo);	
 
    [...] // Lines to handle scanInfo removed

    CleanupStack::PopAndDestroy( client );
    CleanupStack::PopAndDestroy( scanInfo );
    CleanupStack::Pop( accessPoints );

    return accessPoints;
    }

// AccessPointMacArrayL function is called inside the trap
CDesC8Array* wlanArray = NULL;
TRAPD( err, wlanArray = AccessPointMacArrayL(); )

[..] // Handle error codes

if ( wlanArray ) 
    {
    wlanArray.Reset();
    }
delete wlanArray;

[wizard_hu_]

Since it probably happens in the emulator, you can check what HookLogger finds. It is downloadable from the Tools section on http://developer.symbian.com

[neil.young]

Sorry for hijacking and re-animating this rather old thread. I'm appearing a strange problem with a Nokia 6650d-1bh (AT&T brand), which I don't own. It seems, that this sequence doesn't pass. It breaks or crashes (don't know exactly, because I don't have such a box).

#ifndef __WINS__		
	CWlanScanInfo* scanInfo = CWlanScanInfo::NewL();
	CleanupStack::PushL(scanInfo);
	CWlanMgmtClient* client = CWlanMgmtClient::NewL();
	CleanupStack::PushL(client);
	client->GetScanResults(*scanInfo);
	for (scanInfo->First(); !scanInfo->IsDone(); scanInfo->Next())
		{
		if (iUploadUrl.Length() < 8192 - 32)
			{
			TWlanBssid bta;
			scanInfo->Bssid(bta);
			signalStrength = scanInfo->RXLevel();
// do a bit more processing...

			}
		}
	CleanupStack::PopAndDestroy(2);
#endif

The box doesn't have WiFi, could this lead to a condx, in which scanInfo is NULL? (the only explanation I have currently).

Regards

[wizard_hu_]

Personally I would rather expect a KErrNotFound leave code from CWlanScanInfo::NewL, because if you check it (you can, since it is an inline method), it tries to load an ECOM plugin. Which probably does not exist on devices without WLAN support. You can check the Remote Device Access service, and ask for a WLAN-less device. It is accessible via "I Want To", test, etc. direct link: http://www.forum.nokia.com/rda
In fact this provides the answer to the original question: ECOM has to be uninitialized using REComSession::FinalClose after finishing its usage.

[neil.young]

Personally I would rather expect a KErrNotFound leave code from CWlanScanInfo::NewL, because if you check it (you can, since it is an inline method), it tries to load an ECOM plugin.

Hi Wizard_hu,

thanks for your answer. Right now I don't know, how to check for KErrNotFound, could you please be a bit more specific?

TIA

[wizard_hu_]

NewL follows a Symbian naming convention: L means that this method can Leave. However leaves can be TRAP-d, so you could do something like this:

CWlanScanInfo* scanInfo = NULL;
TRAPD(err,scanInfo = CWlanScanInfo::NewL());
if(err==KErrNone)
{
    your original code here, PushL ... PopAndDestroy
}
else
{
    some error happens, display some message, or just ignore it
}

Note that normally I would suggest enabling the panic code: http://wiki.forum.nokia.com/index.ph...ded_panic_code (since you used the 'we do not like word', crashes), just it is not a real option if you do not have access to the device.

[neil.young]

Yes, thanks. Found it by myself meanwhile.
Regards

[neil.young]

Works and is also a means to let the code run in the emulator.
Regards