Chapter 1

Format Argument
type
Interpretation
%d TInt Decimal value of 32-bit signed integer.
%e TReal Real in scientific notation.
%g TReal Real in general format.
%x TUint 32-bit unsigned integer in hexadecimal.
%s TText* String passed as the address of a NULL-terminated string of
Unicode characters.
%S TDesC* String passed as the address of a descriptor
Beware of the difference between %s (for C strings) and %S (for descriptors). Also note that
the descriptor version requires the argument to be a pointer to the descriptor.
The SDK documents the format characters along with its documentation for
TDes::Format(). There are many more options, including width and precision specifiers
and variable argument positions.
8.1.8 RDebug Class
The RDebug class, defined in e32svr.h, includes a host of functions, of which the most
interesting is Print(). If you're debugging under
the emulator, RDebug::Print() prints to the debug output window. If you're debugging on
target hardware, RDebug::Print() uses a serial port, which you can connect to a PC,
using a terminal emulator to view the debug output. The port can be set using HAL::Set(),
specifying EDebugPort and the port number, or if you are using the eshell text shell,
using the debugport command.
This kind of 'print debugging' is useful when a log of activity is handy, or when you have no
access to the debugger. The trade-off is that you need a serial port spare on both your target
hardware and your PC.
8.2 C Standard Library
STDLIB is the Symbian OS implementation of the standard C library. It delivers standard C
functions, which are in general thin layers over corresponding Symbian OS functions.
This means, on the one hand, that you can use almost all your favorite C APIs, from
strlen() and malloc() to fopen() and quicksort(), and on the other, that you can
usually guess the behavior of functions such as User::QuickSort() because they're
there to support standard library functions.
The Symbian OS C standard library was written to support the Java Virtual Machine (JVM)
port, which uses Sun's C source code for the JVM with only minor alterations. By this
measure alone, the standard library is well tested and powerful. It delivers POSIX-compliant
C APIs layering over the Symbian OS user library, file server, and sockets server.
One of STDLIB's design goals was to enable C-language modules to be ported from other
systems – particularly those written for a POSIX-like environment and using the standard C