<?xml version="1.0" encoding="utf-8"?>

<!-- Copyright (c) 2007-2010 Nokia Corporation and/or its subsidiary(-ies) All rights reserved. -->

<!-- This component and the accompanying materials are made available under the terms of the License 

"Eclipse Public License v1.0" which accompanies this distribution, 

and is available at the URL "http://www.eclipse.org/legal/epl-v10.html". -->

<!-- Initial Contributors:

    Nokia Corporation - initial contribution.

Contributors: 

-->

<!DOCTYPE concept

  PUBLIC "-//OASIS//DTD DITA Concept//EN" "concept.dtd">

<concept id="GUID-EA71F52C-DB4C-500D-9051-31BEF29E171D" xml:lang="en"><title>Basic

exception support</title><shortdesc>Describes the operating support for exceptions.</shortdesc><prolog><metadata><keywords/></metadata></prolog><conbody>

<p>The basic operating system support for exceptions comes from</p>

<ul>

<li id="GUID-E168AD4F-366A-5EAF-98F2-0C1B187E1AE0"><p>the <codeph>TRAP</codeph> macro

and its variant, <codeph>TRAPD</codeph>, which allow code to be run under

a <keyword>trap harness</keyword> </p> </li>

<li id="GUID-3B4C9F10-A89C-5979-ABC7-5106C7B9AFED"><p>the <codeph>User::Leave()</codeph> call,

which terminates the current function, and returns to the trap harness, specifying

an error code.</p> </li>

</ul>

<p>These are analogous to C++’s exception handling support (<codeph>try/catch</codeph> and <codeph>throw</codeph>). </p>

<p>By convention, all functions that can leave — directly or indirectly —

have an L appended onto their name (and can therefore be referred to as <keyword>L

functions</keyword>). The function invoked by a trap harness will always be

an L function. </p>