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    10 <!DOCTYPE concept

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

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

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

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

    15 <ul>

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

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

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

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

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

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

    22 </ul>

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

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

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

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

    27 an L function. </p>

    28 </conbody></concept>