examples/Base/MemMan/Cleanup/ELeaveOnFail/ELeaveOnFail.cpp

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Description:
Example shows attempt to construct an object and specifying
(ELeave) after the 'new' operator. 
Specifying (ELeave) causes a leave on failure to allocate memory 
for the new object. 
NOTE: the structure of this example is different to standard E32 examples  
*/



#include <e32cons.h>

//
// Common format text
//

_LIT(KCommonFormat1,"Value of iInt is %d.\n");


  // All messages written to this
LOCAL_D CConsoleBase* console;
  
  // Flag which determines whether the doSomething() member function
  // of the CExample class should leave when called.
LOCAL_D TBool leaveFlag = ETrue;

  // Parameter for __UHEAP_SETFAIL
  // Allocation guaranteed to fail at this number of allocation attempts;
  // i.e. if set to n, allocation fails on the nth attempt. 
  // NB only used in debug mode
#ifdef _DEBUG
LOCAL_D TInt allocFailNumber = 1;
#endif
  
  // Function prototypes
LOCAL_C void doExampleL();      
LOCAL_C void callExampleL();



//
// -----> CExample (definition)
//
// The class is used by the example code
//
class CExample : public CBase
        {
public :
        void DoSomethingL();
public :
        TInt iInt;
        };


//
// -----> CExample (implementation)
//
void CExample::DoSomethingL() 
        {
          // Leave if the global flag is set
        if (leaveFlag)
                {
                _LIT(KMsgLeaving,"DoSomethingL leaving.\n");
                console->Printf(KMsgLeaving);
                User::Leave(KErrGeneral);               
                }
        console->Printf(KCommonFormat1,iInt);
        }

//
// Main function called by E32
//
GLDEF_C TInt E32Main()
    {
          // Get cleanup stack
        CTrapCleanup* cleanup=CTrapCleanup::New();

          // Some more initialization, then do the example
        TRAPD(error,callExampleL());
          
          // callExampleL() should never leave.
        _LIT(KMsgPanicEpoc32ex,"EPOC32EX");
        __ASSERT_ALWAYS(!error,User::Panic(KMsgPanicEpoc32ex,error));

          // destroy the cleanup stack
        delete cleanup;
        
          // return
        return 0;
    }


//
//
//
LOCAL_C void callExampleL() 
    {
          // Initialize and call the example code under cleanup stack.
        _LIT(KMsgExampleCode,"Symbian platform Example Code");
        console = Console::NewL(KMsgExampleCode,TSize(KConsFullScreen,KConsFullScreen));
          // Put console onto the cleanup stack.
        CleanupStack::PushL(console);

          // Perform the example function under the protection of a 
          // TRAP harness.
        TRAPD(error,doExampleL());
        _LIT(KMsgOK,"ok");
        _LIT(KFormat2,"failed: leave code = %d");
        if (error)
                console->Printf(KFormat2,error);
        else
                console->Printf(KMsgOK);
          
          // Continue
        _LIT(KMsgPressAnyKey," [press any key]");
        console->Printf(KMsgPressAnyKey);
        console->Getch();

          // Remove the console object from the cleanupstack
          // and destroy it. 
        CleanupStack::PopAndDestroy();
    }


//
// Do the example
//
void doExampleL()
        {
          // Memory alloc fails on the 'allocFailNumber' attempt. 
          //
          // Note that if you set this to some low value sucah as 1 or 2, then as a side effect,
          // you may also see a dialog box stating "Not enough memory".
        __UHEAP_SETFAIL(RHeap::EDeterministic,allocFailNumber);
          // Allocate - leave if allocation fails.
          // The (ELeave) causes a leave if allocation fails; replaces
          // a call to User::LeaveIfNull(myExample);
          // Compare with the code in LeaveOnFailure
          //
          // Note that the memory allocation will fail and the "new" operation
          // will leave if allocFailNumber is 1.
        CExample* myExample = new (ELeave) CExample;
          // Do something with the CExample object
        myExample->iInt = 5;
          //
        console->Printf(KCommonFormat1,myExample->iInt);
          // Delete the CExample object
        delete myExample;
        }

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