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 <a name="Statements-for-C_002b_002b"></a>
 <div class="header">
 <p>
 Next: <a href="C_002b_002b-Expressions.html#C_002b_002b-Expressions" accesskey="n" rel="next">C++ Expressions</a>, Previous: <a href="Functions-for-C_002b_002b.html#Functions-for-C_002b_002b" accesskey="p" rel="prev">Functions for C++</a>, Up: <a href="C-and-C_002b_002b-Trees.html#C-and-C_002b_002b-Trees" accesskey="u" rel="up">C and C++ Trees</a> &nbsp; [<a href="index.html#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="Option-Index.html#Option-Index" title="Index" rel="index">Index</a>]</p>
 </div>
 <hr>
 <a name="Statements-for-C_002b_002b-1"></a>
 <h4 class="subsection">10.10.5 Statements for C++</h4>
 <a name="index-statements-1"></a>
 <a name="index-BREAK_005fSTMT"></a>
 <a name="index-CLEANUP_005fSTMT"></a>
 <a name="index-CLEANUP_005fDECL"></a>
 <a name="index-CLEANUP_005fEXPR"></a>
 <a name="index-CONTINUE_005fSTMT"></a>
 <a name="index-DECL_005fSTMT"></a>
 <a name="index-DECL_005fSTMT_005fDECL"></a>
 <a name="index-DO_005fSTMT"></a>
 <a name="index-DO_005fBODY"></a>
 <a name="index-DO_005fCOND"></a>
 <a name="index-EMPTY_005fCLASS_005fEXPR"></a>
 <a name="index-EXPR_005fSTMT"></a>
 <a name="index-EXPR_005fSTMT_005fEXPR"></a>
 <a name="index-FOR_005fSTMT"></a>
 <a name="index-FOR_005fINIT_005fSTMT"></a>
 <a name="index-FOR_005fCOND"></a>
 <a name="index-FOR_005fEXPR"></a>
 <a name="index-FOR_005fBODY"></a>
 <a name="index-HANDLER"></a>
 <a name="index-IF_005fSTMT"></a>
 <a name="index-IF_005fCOND"></a>
 <a name="index-THEN_005fCLAUSE"></a>
 <a name="index-ELSE_005fCLAUSE"></a>
 <a name="index-RETURN_005fSTMT"></a>
 <a name="index-RETURN_005fEXPR"></a>
 <a name="index-SUBOBJECT"></a>
 <a name="index-SUBOBJECT_005fCLEANUP"></a>
 <a name="index-SWITCH_005fSTMT"></a>
 <a name="index-SWITCH_005fCOND"></a>
 <a name="index-SWITCH_005fBODY"></a>
 <a name="index-TRY_005fBLOCK"></a>
 <a name="index-TRY_005fSTMTS"></a>
 <a name="index-TRY_005fHANDLERS"></a>
 <a name="index-HANDLER_005fPARMS"></a>
 <a name="index-HANDLER_005fBODY"></a>
 <a name="index-USING_005fSTMT"></a>
 <a name="index-WHILE_005fSTMT"></a>
 <a name="index-WHILE_005fBODY"></a>
 <a name="index-WHILE_005fCOND"></a>

 <p>A function that has a definition in the current translation unit will
 have a non-<code>NULL</code> <code>DECL_INITIAL</code>.  However, back ends should not make
 use of the particular value given by <code>DECL_INITIAL</code>.
 </p>
 <p>The <code>DECL_SAVED_TREE</code> macro will give the complete body of the
 function.
 </p>
 <a name="Statements-2"></a>
 <h4 class="subsubsection">10.10.5.1 Statements</h4>

 <p>There are tree nodes corresponding to all of the source-level
 statement constructs, used within the C and C++ frontends.  These are
 enumerated here, together with a list of the various macros that can
 be used to obtain information about them.  There are a few macros that
 can be used with all statements:
 </p>
 <dl compact="compact">
 <dt><code>STMT_IS_FULL_EXPR_P</code>
 <a name="index-STMT_005fIS_005fFULL_005fEXPR_005fP"></a>
 </dt>
 <dd><p>In C++, statements normally constitute &ldquo;full expressions&rdquo;; temporaries
 created during a statement are destroyed when the statement is complete.
 However, G++ sometimes represents expressions by statements; these
 statements will not have <code>STMT_IS_FULL_EXPR_P</code> set.  Temporaries
 created during such statements should be destroyed when the innermost
 enclosing statement with <code>STMT_IS_FULL_EXPR_P</code> set is exited.
 </p>
 </dd>
 </dl>

 <p>Here is the list of the various statement nodes, and the macros used to
 access them.  This documentation describes the use of these nodes in
 non-template functions (including instantiations of template functions).
 In template functions, the same nodes are used, but sometimes in
 slightly different ways.
 </p>
 <p>Many of the statements have substatements.  For example, a <code>while</code>
 loop will have a body, which is itself a statement.  If the substatement
 is <code>NULL_TREE</code>, it is considered equivalent to a statement
 consisting of a single <code>;</code>, i.e., an expression statement in which
 the expression has been omitted.  A substatement may in fact be a list
 of statements, connected via their <code>TREE_CHAIN</code>s.  So, you should
 always process the statement tree by looping over substatements, like
 this:
 </p><div class="smallexample">
 <pre class="smallexample">void process_stmt (stmt)
      tree stmt;
 {
   while (stmt)
     {
       switch (TREE_CODE (stmt))
         {
         case IF_STMT:
           process_stmt (THEN_CLAUSE (stmt));
           /* <span class="roman">More processing here.</span>  */
           break;

         &hellip;
         }

       stmt = TREE_CHAIN (stmt);
     }
 }
 </pre></div>
 <p>In other words, while the <code>then</code> clause of an <code>if</code> statement
 in C++ can be only one statement (although that one statement may be a
 compound statement), the intermediate representation will sometimes use
 several statements chained together.
 </p>
 <dl compact="compact">
 <dt><code>BREAK_STMT</code></dt>
 <dd>
 <p>Used to represent a <code>break</code> statement.  There are no additional
 fields.
 </p>
 </dd>
 <dt><code>CILK_SPAWN_STMT</code></dt>
 <dd>
 <p>Used to represent a spawning function in the Cilk Plus language extension.
 This tree has one field that holds the name of the spawning function.
 <code>_Cilk_spawn</code> can be written in C in the following way:
 </p>
 <div class="smallexample">
 <pre class="smallexample"><code>_Cilk_spawn</code> &lt;function_name&gt; (&lt;parameters&gt;);
 </pre></div>

 <p>Detailed description for usage and functionality of <code>_Cilk_spawn</code> can be
 found at http://www.cilkplus.org
 </p>
 </dd>
 <dt><code>CILK_SYNC_STMT</code></dt>
 <dd>
 <p>This statement is part of the Cilk Plus language extension.  It indicates that
 the current function cannot continue in parallel with its spawned children.
 There are no additional fields.  <code>_Cilk_sync</code> can be written in C in the
 following way:
 </p>
 <div class="smallexample">
 <pre class="smallexample"><code>_Cilk_sync</code>;
 </pre></div>

 </dd>
 <dt><code>CLEANUP_STMT</code></dt>
 <dd>
 <p>Used to represent an action that should take place upon exit from the
 enclosing scope.  Typically, these actions are calls to destructors for
 local objects, but back ends cannot rely on this fact.  If these nodes
 are in fact representing such destructors, <code>CLEANUP_DECL</code> will be
 the <code>VAR_DECL</code> destroyed.  Otherwise, <code>CLEANUP_DECL</code> will be
 <code>NULL_TREE</code>.  In any case, the <code>CLEANUP_EXPR</code> is the
 expression to execute.  The cleanups executed on exit from a scope
 should be run in the reverse order of the order in which the associated
 <code>CLEANUP_STMT</code>s were encountered.
 </p>
 </dd>
 <dt><code>CONTINUE_STMT</code></dt>
 <dd>
 <p>Used to represent a <code>continue</code> statement.  There are no additional
 fields.
 </p>
 </dd>
 <dt><code>CTOR_STMT</code></dt>
 <dd>
 <p>Used to mark the beginning (if <code>CTOR_BEGIN_P</code> holds) or end (if
 <code>CTOR_END_P</code> holds of the main body of a constructor.  See also
 <code>SUBOBJECT</code> for more information on how to use these nodes.
 </p>
 </dd>
 <dt><code>DO_STMT</code></dt>
 <dd>
 <p>Used to represent a <code>do</code> loop.  The body of the loop is given by
 <code>DO_BODY</code> while the termination condition for the loop is given by
 <code>DO_COND</code>.  The condition for a <code>do</code>-statement is always an
 expression.
 </p>
 </dd>
 <dt><code>EMPTY_CLASS_EXPR</code></dt>
 <dd>
 <p>Used to represent a temporary object of a class with no data whose
 address is never taken.  (All such objects are interchangeable.)  The
 <code>TREE_TYPE</code> represents the type of the object.
 </p>
 </dd>
 <dt><code>EXPR_STMT</code></dt>
 <dd>
 <p>Used to represent an expression statement.  Use <code>EXPR_STMT_EXPR</code> to
 obtain the expression.
 </p>
 </dd>
 <dt><code>FOR_STMT</code></dt>
 <dd>
 <p>Used to represent a <code>for</code> statement.  The <code>FOR_INIT_STMT</code> is
 the initialization statement for the loop.  The <code>FOR_COND</code> is the
 termination condition.  The <code>FOR_EXPR</code> is the expression executed
 right before the <code>FOR_COND</code> on each loop iteration; often, this
 expression increments a counter.  The body of the loop is given by
 <code>FOR_BODY</code>.  Note that <code>FOR_INIT_STMT</code> and <code>FOR_BODY</code>
 return statements, while <code>FOR_COND</code> and <code>FOR_EXPR</code> return
 expressions.
 </p>
 </dd>
 <dt><code>HANDLER</code></dt>
 <dd>
 <p>Used to represent a C++ <code>catch</code> block.  The <code>HANDLER_TYPE</code>
 is the type of exception that will be caught by this handler; it is
 equal (by pointer equality) to <code>NULL</code> if this handler is for all
 types.  <code>HANDLER_PARMS</code> is the <code>DECL_STMT</code> for the catch
 parameter, and <code>HANDLER_BODY</code> is the code for the block itself.
 </p>
 </dd>
 <dt><code>IF_STMT</code></dt>
 <dd>
 <p>Used to represent an <code>if</code> statement.  The <code>IF_COND</code> is the
 expression.
 </p>
 <p>If the condition is a <code>TREE_LIST</code>, then the <code>TREE_PURPOSE</code> is
 a statement (usually a <code>DECL_STMT</code>).  Each time the condition is
 evaluated, the statement should be executed.  Then, the
 <code>TREE_VALUE</code> should be used as the conditional expression itself.
 This representation is used to handle C++ code like this:
 </p>
 <p>C++ distinguishes between this and <code>COND_EXPR</code> for handling templates.
 </p>
 <div class="smallexample">
 <pre class="smallexample">if (int i = 7) &hellip;
 </pre></div>

 <p>where there is a new local variable (or variables) declared within the
 condition.
 </p>
 <p>The <code>THEN_CLAUSE</code> represents the statement given by the <code>then</code>
 condition, while the <code>ELSE_CLAUSE</code> represents the statement given
 by the <code>else</code> condition.
 </p>
 </dd>
 <dt><code>SUBOBJECT</code></dt>
 <dd>
 <p>In a constructor, these nodes are used to mark the point at which a
 subobject of <code>this</code> is fully constructed.  If, after this point, an
 exception is thrown before a <code>CTOR_STMT</code> with <code>CTOR_END_P</code> set
 is encountered, the <code>SUBOBJECT_CLEANUP</code> must be executed.  The
 cleanups must be executed in the reverse order in which they appear.
 </p>
 </dd>
 <dt><code>SWITCH_STMT</code></dt>
 <dd>
 <p>Used to represent a <code>switch</code> statement.  The <code>SWITCH_STMT_COND</code>
 is the expression on which the switch is occurring.  See the documentation
 for an <code>IF_STMT</code> for more information on the representation used
 for the condition.  The <code>SWITCH_STMT_BODY</code> is the body of the switch
 statement.   The <code>SWITCH_STMT_TYPE</code> is the original type of switch
 expression as given in the source, before any compiler conversions.
 </p>
 </dd>
 <dt><code>TRY_BLOCK</code></dt>
 <dd><p>Used to represent a <code>try</code> block.  The body of the try block is
 given by <code>TRY_STMTS</code>.  Each of the catch blocks is a <code>HANDLER</code>
 node.  The first handler is given by <code>TRY_HANDLERS</code>.  Subsequent
 handlers are obtained by following the <code>TREE_CHAIN</code> link from one
 handler to the next.  The body of the handler is given by
 <code>HANDLER_BODY</code>.
 </p>
 <p>If <code>CLEANUP_P</code> holds of the <code>TRY_BLOCK</code>, then the
 <code>TRY_HANDLERS</code> will not be a <code>HANDLER</code> node.  Instead, it will
 be an expression that should be executed if an exception is thrown in
 the try block.  It must rethrow the exception after executing that code.
 And, if an exception is thrown while the expression is executing,
 <code>terminate</code> must be called.
 </p>
 </dd>
 <dt><code>USING_STMT</code></dt>
 <dd><p>Used to represent a <code>using</code> directive.  The namespace is given by
 <code>USING_STMT_NAMESPACE</code>, which will be a NAMESPACE_DECL.  This node
 is needed inside template functions, to implement using directives
 during instantiation.
 </p>
 </dd>
 <dt><code>WHILE_STMT</code></dt>
 <dd>
 <p>Used to represent a <code>while</code> loop.  The <code>WHILE_COND</code> is the
 termination condition for the loop.  See the documentation for an
 <code>IF_STMT</code> for more information on the representation used for the
 condition.
 </p>
 <p>The <code>WHILE_BODY</code> is the body of the loop.
 </p>
 </dd>
 </dl>

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 Next: <a href="C_002b_002b-Expressions.html#C_002b_002b-Expressions" accesskey="n" rel="next">C++ Expressions</a>, Previous: <a href="Functions-for-C_002b_002b.html#Functions-for-C_002b_002b" accesskey="p" rel="prev">Functions for C++</a>, Up: <a href="C-and-C_002b_002b-Trees.html#C-and-C_002b_002b-Trees" accesskey="u" rel="up">C and C++ Trees</a> &nbsp; [<a href="index.html#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="Option-Index.html#Option-Index" title="Index" rel="index">Index</a>]</p>
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	<a name="Statements-for-C_002b_002b"></a>
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	<p>
	Next: <a href="C_002b_002b-Expressions.html#C_002b_002b-Expressions" accesskey="n" rel="next">C++ Expressions</a>, Previous: <a href="Functions-for-C_002b_002b.html#Functions-for-C_002b_002b" accesskey="p" rel="prev">Functions for C++</a>, Up: <a href="C-and-C_002b_002b-Trees.html#C-and-C_002b_002b-Trees" accesskey="u" rel="up">C and C++ Trees</a>   [<a href="index.html#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="Option-Index.html#Option-Index" title="Index" rel="index">Index</a>]</p>
	</div>
	<hr>
	<a name="Statements-for-C_002b_002b-1"></a>
	<h4 class="subsection">10.10.5 Statements for C++</h4>
	<a name="index-statements-1"></a>
	<a name="index-BREAK_005fSTMT"></a>
	<a name="index-CLEANUP_005fSTMT"></a>
	<a name="index-CLEANUP_005fDECL"></a>
	<a name="index-CLEANUP_005fEXPR"></a>
	<a name="index-CONTINUE_005fSTMT"></a>
	<a name="index-DECL_005fSTMT"></a>
	<a name="index-DECL_005fSTMT_005fDECL"></a>
	<a name="index-DO_005fSTMT"></a>
	<a name="index-DO_005fBODY"></a>
	<a name="index-DO_005fCOND"></a>
	<a name="index-EMPTY_005fCLASS_005fEXPR"></a>
	<a name="index-EXPR_005fSTMT"></a>
	<a name="index-EXPR_005fSTMT_005fEXPR"></a>
	<a name="index-FOR_005fSTMT"></a>
	<a name="index-FOR_005fINIT_005fSTMT"></a>
	<a name="index-FOR_005fCOND"></a>
	<a name="index-FOR_005fEXPR"></a>
	<a name="index-FOR_005fBODY"></a>
	<a name="index-HANDLER"></a>
	<a name="index-IF_005fSTMT"></a>
	<a name="index-IF_005fCOND"></a>
	<a name="index-THEN_005fCLAUSE"></a>
	<a name="index-ELSE_005fCLAUSE"></a>
	<a name="index-RETURN_005fSTMT"></a>
	<a name="index-RETURN_005fEXPR"></a>
	<a name="index-SUBOBJECT"></a>
	<a name="index-SUBOBJECT_005fCLEANUP"></a>
	<a name="index-SWITCH_005fSTMT"></a>
	<a name="index-SWITCH_005fCOND"></a>
	<a name="index-SWITCH_005fBODY"></a>
	<a name="index-TRY_005fBLOCK"></a>
	<a name="index-TRY_005fSTMTS"></a>
	<a name="index-TRY_005fHANDLERS"></a>
	<a name="index-HANDLER_005fPARMS"></a>
	<a name="index-HANDLER_005fBODY"></a>
	<a name="index-USING_005fSTMT"></a>
	<a name="index-WHILE_005fSTMT"></a>
	<a name="index-WHILE_005fBODY"></a>
	<a name="index-WHILE_005fCOND"></a>

	<p>A function that has a definition in the current translation unit will
	have a non-<code>NULL</code> <code>DECL_INITIAL</code>. However, back ends should not make
	use of the particular value given by <code>DECL_INITIAL</code>.
	</p>
	<p>The <code>DECL_SAVED_TREE</code> macro will give the complete body of the
	function.
	</p>
	<a name="Statements-2"></a>
	<h4 class="subsubsection">10.10.5.1 Statements</h4>

	<p>There are tree nodes corresponding to all of the source-level
	statement constructs, used within the C and C++ frontends. These are
	enumerated here, together with a list of the various macros that can
	be used to obtain information about them. There are a few macros that
	can be used with all statements:
	</p>
	<dl compact="compact">
	<dt><code>STMT_IS_FULL_EXPR_P</code>
	<a name="index-STMT_005fIS_005fFULL_005fEXPR_005fP"></a>
	</dt>
	<dd><p>In C++, statements normally constitute “full expressions”; temporaries
	created during a statement are destroyed when the statement is complete.
	However, G++ sometimes represents expressions by statements; these
	statements will not have <code>STMT_IS_FULL_EXPR_P</code> set. Temporaries
	created during such statements should be destroyed when the innermost
	enclosing statement with <code>STMT_IS_FULL_EXPR_P</code> set is exited.
	</p>
	</dd>
	</dl>

	<p>Here is the list of the various statement nodes, and the macros used to
	access them. This documentation describes the use of these nodes in
	non-template functions (including instantiations of template functions).
	In template functions, the same nodes are used, but sometimes in
	slightly different ways.
	</p>
	<p>Many of the statements have substatements. For example, a <code>while</code>
	loop will have a body, which is itself a statement. If the substatement
	is <code>NULL_TREE</code>, it is considered equivalent to a statement
	consisting of a single <code>;</code>, i.e., an expression statement in which
	the expression has been omitted. A substatement may in fact be a list
	of statements, connected via their <code>TREE_CHAIN</code>s. So, you should
	always process the statement tree by looping over substatements, like
	this:
	</p><div class="smallexample">
	<pre class="smallexample">void process_stmt (stmt)
	tree stmt;
	{
	while (stmt)
	{
	switch (TREE_CODE (stmt))
	{
	case IF_STMT:
	process_stmt (THEN_CLAUSE (stmt));
	/* <span class="roman">More processing here.</span> */
	break;

	…
	}

	stmt = TREE_CHAIN (stmt);
	}
	}
	</pre></div>
	<p>In other words, while the <code>then</code> clause of an <code>if</code> statement
	in C++ can be only one statement (although that one statement may be a
	compound statement), the intermediate representation will sometimes use
	several statements chained together.
	</p>
	<dl compact="compact">
	<dt><code>BREAK_STMT</code></dt>
	<dd>
	<p>Used to represent a <code>break</code> statement. There are no additional
	fields.
	</p>
	</dd>
	<dt><code>CILK_SPAWN_STMT</code></dt>
	<dd>
	<p>Used to represent a spawning function in the Cilk Plus language extension.
	This tree has one field that holds the name of the spawning function.
	<code>_Cilk_spawn</code> can be written in C in the following way:
	</p>
	<div class="smallexample">
	<pre class="smallexample"><code>_Cilk_spawn</code> <function_name> (<parameters>);
	</pre></div>

	<p>Detailed description for usage and functionality of <code>_Cilk_spawn</code> can be
	found at http://www.cilkplus.org
	</p>
	</dd>
	<dt><code>CILK_SYNC_STMT</code></dt>
	<dd>
	<p>This statement is part of the Cilk Plus language extension. It indicates that
	the current function cannot continue in parallel with its spawned children.
	There are no additional fields. <code>_Cilk_sync</code> can be written in C in the
	following way:
	</p>
	<div class="smallexample">
	<pre class="smallexample"><code>_Cilk_sync</code>;
	</pre></div>

	</dd>
	<dt><code>CLEANUP_STMT</code></dt>
	<dd>
	<p>Used to represent an action that should take place upon exit from the
	enclosing scope. Typically, these actions are calls to destructors for
	local objects, but back ends cannot rely on this fact. If these nodes
	are in fact representing such destructors, <code>CLEANUP_DECL</code> will be
	the <code>VAR_DECL</code> destroyed. Otherwise, <code>CLEANUP_DECL</code> will be
	<code>NULL_TREE</code>. In any case, the <code>CLEANUP_EXPR</code> is the
	expression to execute. The cleanups executed on exit from a scope
	should be run in the reverse order of the order in which the associated
	<code>CLEANUP_STMT</code>s were encountered.
	</p>
	</dd>
	<dt><code>CONTINUE_STMT</code></dt>
	<dd>
	<p>Used to represent a <code>continue</code> statement. There are no additional
	fields.
	</p>
	</dd>
	<dt><code>CTOR_STMT</code></dt>
	<dd>
	<p>Used to mark the beginning (if <code>CTOR_BEGIN_P</code> holds) or end (if
	<code>CTOR_END_P</code> holds of the main body of a constructor. See also
	<code>SUBOBJECT</code> for more information on how to use these nodes.
	</p>
	</dd>
	<dt><code>DO_STMT</code></dt>
	<dd>
	<p>Used to represent a <code>do</code> loop. The body of the loop is given by
	<code>DO_BODY</code> while the termination condition for the loop is given by
	<code>DO_COND</code>. The condition for a <code>do</code>-statement is always an
	expression.
	</p>
	</dd>
	<dt><code>EMPTY_CLASS_EXPR</code></dt>
	<dd>
	<p>Used to represent a temporary object of a class with no data whose
	address is never taken. (All such objects are interchangeable.) The
	<code>TREE_TYPE</code> represents the type of the object.
	</p>
	</dd>
	<dt><code>EXPR_STMT</code></dt>
	<dd>
	<p>Used to represent an expression statement. Use <code>EXPR_STMT_EXPR</code> to
	obtain the expression.
	</p>
	</dd>
	<dt><code>FOR_STMT</code></dt>
	<dd>
	<p>Used to represent a <code>for</code> statement. The <code>FOR_INIT_STMT</code> is
	the initialization statement for the loop. The <code>FOR_COND</code> is the
	termination condition. The <code>FOR_EXPR</code> is the expression executed
	right before the <code>FOR_COND</code> on each loop iteration; often, this
	expression increments a counter. The body of the loop is given by
	<code>FOR_BODY</code>. Note that <code>FOR_INIT_STMT</code> and <code>FOR_BODY</code>
	return statements, while <code>FOR_COND</code> and <code>FOR_EXPR</code> return
	expressions.
	</p>
	</dd>
	<dt><code>HANDLER</code></dt>
	<dd>
	<p>Used to represent a C++ <code>catch</code> block. The <code>HANDLER_TYPE</code>
	is the type of exception that will be caught by this handler; it is
	equal (by pointer equality) to <code>NULL</code> if this handler is for all
	types. <code>HANDLER_PARMS</code> is the <code>DECL_STMT</code> for the catch
	parameter, and <code>HANDLER_BODY</code> is the code for the block itself.
	</p>
	</dd>
	<dt><code>IF_STMT</code></dt>
	<dd>
	<p>Used to represent an <code>if</code> statement. The <code>IF_COND</code> is the
	expression.
	</p>
	<p>If the condition is a <code>TREE_LIST</code>, then the <code>TREE_PURPOSE</code> is
	a statement (usually a <code>DECL_STMT</code>). Each time the condition is
	evaluated, the statement should be executed. Then, the
	<code>TREE_VALUE</code> should be used as the conditional expression itself.
	This representation is used to handle C++ code like this:
	</p>
	<p>C++ distinguishes between this and <code>COND_EXPR</code> for handling templates.
	</p>
	<div class="smallexample">
	<pre class="smallexample">if (int i = 7) …
	</pre></div>

	<p>where there is a new local variable (or variables) declared within the
	condition.
	</p>
	<p>The <code>THEN_CLAUSE</code> represents the statement given by the <code>then</code>
	condition, while the <code>ELSE_CLAUSE</code> represents the statement given
	by the <code>else</code> condition.
	</p>
	</dd>
	<dt><code>SUBOBJECT</code></dt>
	<dd>
	<p>In a constructor, these nodes are used to mark the point at which a
	subobject of <code>this</code> is fully constructed. If, after this point, an
	exception is thrown before a <code>CTOR_STMT</code> with <code>CTOR_END_P</code> set
	is encountered, the <code>SUBOBJECT_CLEANUP</code> must be executed. The
	cleanups must be executed in the reverse order in which they appear.
	</p>
	</dd>
	<dt><code>SWITCH_STMT</code></dt>
	<dd>
	<p>Used to represent a <code>switch</code> statement. The <code>SWITCH_STMT_COND</code>
	is the expression on which the switch is occurring. See the documentation
	for an <code>IF_STMT</code> for more information on the representation used
	for the condition. The <code>SWITCH_STMT_BODY</code> is the body of the switch
	statement. The <code>SWITCH_STMT_TYPE</code> is the original type of switch
	expression as given in the source, before any compiler conversions.
	</p>
	</dd>
	<dt><code>TRY_BLOCK</code></dt>
	<dd><p>Used to represent a <code>try</code> block. The body of the try block is
	given by <code>TRY_STMTS</code>. Each of the catch blocks is a <code>HANDLER</code>
	node. The first handler is given by <code>TRY_HANDLERS</code>. Subsequent
	handlers are obtained by following the <code>TREE_CHAIN</code> link from one
	handler to the next. The body of the handler is given by
	<code>HANDLER_BODY</code>.
	</p>
	<p>If <code>CLEANUP_P</code> holds of the <code>TRY_BLOCK</code>, then the
	<code>TRY_HANDLERS</code> will not be a <code>HANDLER</code> node. Instead, it will
	be an expression that should be executed if an exception is thrown in
	the try block. It must rethrow the exception after executing that code.
	And, if an exception is thrown while the expression is executing,
	<code>terminate</code> must be called.
	</p>
	</dd>
	<dt><code>USING_STMT</code></dt>
	<dd><p>Used to represent a <code>using</code> directive. The namespace is given by
	<code>USING_STMT_NAMESPACE</code>, which will be a NAMESPACE_DECL. This node
	is needed inside template functions, to implement using directives
	during instantiation.
	</p>
	</dd>
	<dt><code>WHILE_STMT</code></dt>
	<dd>
	<p>Used to represent a <code>while</code> loop. The <code>WHILE_COND</code> is the
	termination condition for the loop. See the documentation for an
	<code>IF_STMT</code> for more information on the representation used for the
	condition.
	</p>
	<p>The <code>WHILE_BODY</code> is the body of the loop.
	</p>
	</dd>
	</dl>

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