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<concept id="GUID-BE893F87-E7F6-56E5-BD27-328B532F8332" xml:lang="en"><title>Hello
World Example: Using P.I.P.S.</title><prolog><metadata><keywords/></metadata></prolog><conbody>
<p>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 <filepath>libdl</filepath> library to
implement this lookup by name mechanism. </p>
<p>The example defines a simple DLL using the P.I.P.S. <codeph>STDDLL</codeph> target
type, with an exported function. It also creates a simple EXE, using the <codeph>STDEXE</codeph> 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. </p>
<section><title>Download</title> <p>Click on the following link to download
the example: <xref href="guid-6013a680-57f9-415b-8851-c4fa63356636/zips/guid-42af5ea2-87c6-46ef-b872-af35876c73c7.zip" scope="external">HelloWorldExample.zip</xref></p><p>Click: <xref href="guid-6013a680-57f9-415b-8851-c4fa63356636/guid-42af5ea2-87c6-46ef-b872-af35876c73c7.html" scope="peer">browse</xref> to view the example code. </p> </section>
<section><title>Description</title> <p>The following sections provide more
information about the example. </p> <p><b> Creating a simple DLL using P.I.P.S.
STDDLL target type</b> </p> <p>The example creates a DLL file that declares
and defines an exported function. The target type of this DLL file is <codeph>STDDLL</codeph>.
It contains a header and a source file: </p> <ul>
<li id="GUID-A0857840-AD8C-5313-A642-801A79382855"><p> <filepath>helloworlddllexample.h</filepath>:
this declares a function with external linkage. Note that for a <codeph>STDDLL</codeph> library,
functions and data with external linkage are exported by default, without
any requirement for <codeph>IMPORT_C</codeph> and <codeph>EXPORT_C</codeph> declarations
in header or source files. </p> </li>
<li id="GUID-973CE8AE-5B87-5234-8145-20A6632E7F9C"><p> <filepath>helloworlddllexample.cpp</filepath>:
this defines the function declared in the header file, which displays a hello
world message to the console. </p> </li>
</ul> <p><b> Creating a simple EXE using P.I.P.S. STDEXE target type</b> </p> <p>The
example creates an EXE file which calls the exported function of the loaded
DLL. The target type of this EXE file is <codeph>STDEXE</codeph>. It calls
the following <filepath>libdl</filepath> functions to use the lookup by name
mechanism: </p> <ul>
<li id="GUID-08422DA9-EE4F-502C-8D31-EB19BC86F98B"><p> <xref href="GUID-51FB35C0-CFC2-357A-8ACA-FE7480C53AD3.dita"><apiname>dlopen()</apiname></xref>:
This function is used to load the DLL file which contains an exported function. </p> </li>
</ul> <ul>
<li id="GUID-0EC17FCA-7B6A-5FBF-8693-1C4BD629F553"><p> <xref href="GUID-312604D7-59D9-3C67-9D4F-42CFA24EAA2B.dita"><apiname>dlsysm()</apiname></xref>:
This function gets the address of a symbol defined within the DLL loaded by
the <codeph>dlopen()</codeph> call. </p> </li>
</ul> <ul>
<li id="GUID-EFC5BA53-F378-5D2B-A550-1055DA8CBAD7"><p> <xref href="GUID-F74DC7CB-1E3F-368E-99A7-DD4B38FF7EF0.dita"><apiname>dlclose()</apiname></xref>:
This function informs the system that the DLL loaded by a previous <codeph>dlopen()</codeph> call
is no longer needed by the application. </p> </li>
</ul> <ul>
<li id="GUID-B6003F4A-8919-5D15-844E-294A9020A2C2"><p> <xref href="GUID-F5B2CFAB-99F5-3A24-8F6C-ECAA61922FB0.dita"><apiname>dlerror()</apiname></xref>:
This function is used to get the last error that occurred from any of the <filepath>libdl</filepath> APIs. </p> </li>
</ul> <p>The EXE links to <filepath>libdl.lib</filepath> to use these functions. </p> </section>
<section><title>Build</title> <p>The <xref href="GUID-3100800B-B2F7-50EF-BD4C-3C345ECCB2A5.dita">Symbian
build process</xref> describes how to build this example application. </p> <p>The <filepath>HelloWorldExample</filepath> builds
two files, a DLL file <filepath>helloworlddllexample.dll</filepath>, and an
EXE file <filepath>helloworldexeexample.exe</filepath>, in the standard locations. </p> <p>To
run the example, start <filepath>helloworldexeexample.exe</filepath> 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. </p> </section>
</conbody></concept>