Hello +World Example: Using P.I.P.S.

This example application shows a simple EXE and DLL written using P.I.P.S. +(P.I.P.S. Is POSIX on Symbian Platform). It also shows the dynamic lookup +of symbols by name mechanism used in Unix-like operating systems, instead +of the native Symbian Platform lookup by ordinal mechanism. P.I.P.S., from +Symbian OS v9.3, provides APIs from libdl library to +implement this lookup by name mechanism.

The example defines a simple DLL using the P.I.P.S. STDDLL target +type, with an exported function. It also creates a simple EXE, using the STDEXE target +type, which calls the DLL's exported function using the lookup by name mechanism. +These P.I.P.S. specific target types are required to enable the specific options +for compilers and linkers to generate P.I.P.S. executables and to make symbol +information available in the executable image.

Description

The following sections provide more +information about the example.

Creating a simple DLL using P.I.P.S. +STDDLL target type

The example creates a DLL file that declares +and defines an exported function. The target type of this DLL file is STDDLL. +It contains a header and a source file:

helloworlddllexample.h: +this declares a function with external linkage. Note that for a STDDLL library, +functions and data with external linkage are exported by default, without +any requirement for IMPORT_C and EXPORT_C declarations +in header or source files.
helloworlddllexample.cpp: +this defines the function declared in the header file, which displays a hello +world message to the console.

Creating a simple EXE using P.I.P.S. STDEXE target type

The +example creates an EXE file which calls the exported function of the loaded +DLL. The target type of this EXE file is STDEXE. It calls +the following libdl functions to use the lookup by name +mechanism:

dlopen(): +This function is used to load the DLL file which contains an exported function.

dlsysm(): +This function gets the address of a symbol defined within the DLL loaded by +the dlopen() call.

dlclose(): +This function informs the system that the DLL loaded by a previous dlopen() call +is no longer needed by the application.

dlerror(): +This function is used to get the last error that occurred from any of the libdl APIs.

The EXE links to libdl.lib to use these functions.

Build

The Symbian +build process describes how to build this example application.

The HelloWorldExample builds +two files, a DLL file helloworlddllexample.dll, and an +EXE file helloworldexeexample.exe, in the standard locations.

To +run the example, start helloworldexeexample.exe from +the file system or from your IDE. After launching the executable, depending +on the emulator you are using, you may need to navigate away from the application +launcher or shell screen to view the console.