Chapter 1

marking a function GLDEF_C, you show that you have thought about it being exported from
the object module. E32Main() returns an integer – a TInt. You could have written int
instead of TInt, but since C++ compilers don't guarantee that int is a 32-bit signed integer,
Symbian OS uses typedefs for standard types to make sure they are guaranteed to be the
same across all Symbian OS implementations and compilers.
E32Main() sets up an error-handling framework. It sets up a cleanup stack and then calls
ConsoleMainL() under a trap harness. The trap harness catches errors – more precisely,
it catches any functions that leave. If you're familiar with the exception handling in standard
C++ or Java, TRAP() is like try and catch all in one, User::Leave() is like throw, and a
function with L at the end of its name is like a function with throws in its prototype. It's very
important to know what these functions are: the Symbian OS convention is to give them a
name ending in L().
Here's ConsoleMainL():
// Console harness
void ConsoleMainL()
{
// Get a console
gConsole = Console::NewL(_L("Hello Text"),
CleanupStack::PushL(gConsole);
// Call function
MainL();
// Pause before terminating
User::After(5000000); // 5 second delay
// Finished with console
CleanupStack::PopAndDestroy(gConsole);
}
TSize(KConsFullScreen, KConsFullScreen));
This function allocates a console before calling MainL() to do the Printf() of the 'Hello
world!' message. After that, it briefly pauses and then deletes the console again. If we were
creating this example for a target machine that had a keyboard, we could have replaced the
delay code:
// Pause before terminating
User::After(5000000); // 5 second delay
with something like:
// Wait for key
console->Printf(_L("[ press any key ]"));
console->Getch(); // Get and ignore character
so that the application would wait for a keypress before terminating.