_LIT( KFileName, "C:\\data\\others\\test.txt" );
_LIT( KText, "C:\\data\\others\\txtt.txt");
RFs fsSession;
User:

eaveIfError(fsSession.Connect());
CleanupClosePushL( fsSession );
TInt err = fsSession.MkDirAll(KFileName);
if ( (KErrNone != err) && (KErrAlreadyExists != err) )
{
CleanupStack:

opAndDestroy(1); // fsSession
return;
}
RFile file;
err = file.Replace(fsSession, KFileName, EFileWrite );
CleanupClosePushL( file );
if ( KErrNone != err )
{
CleanupStack:

opAndDestroy(2); // file, fsSession
return;
}
RFile filess;
err = filess.Open(fsSession, KText, EFileRead);
CleanupClosePushL( filess );
if ( KErrNone != err )
{
CleanupStack:

opAndDestroy();
return;
}
RFileWriteStream outputFileStream( file );
CleanupClosePushL( outputFileStream );
outputFileStream << filess ;
CleanupStack:

opAndDestroy(3);
fsSession.Close();
报错:
..\..\..\epoc32\include\s32strm.inl (instantiating: 'DoExternalizeL<RFile>(const RFile &, RWriteStream &, Externalize::Member)')
Why?