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<HTML><HEAD><TITLE><exception></TITLE></HEAD><BODY><H1><A NAME="<exception>"><CODE><exception></CODE></A></H1><HR><P>Include the standard header <B><CODE><exception></CODE></B>to define several types and functions related to the handlingof exceptions.</P><PRE> // DECLARATIONSclass <B><A HREF="#exception">exception</A></B>;class <B><A HREF="#bad_exception">bad_exception</A></B>; // FUNCTIONStypedef void (*<B><A HREF="#terminate_handler">terminate_handler</A></B>)();typedef void (*<B><A HREF="#unexpected_handler">unexpected_handler</A></B>)();terminate_handler <B><A HREF="#set_terminate">set_terminate</A></B>(terminate_handler pnew) throw();unexpected_handler <B><A HREF="#set_unexpected">set_unexpected</A></B>(unexpected_handler pnew) throw();void <B><A HREF="#terminate">terminate</A></B>();void <B><A HREF="#unexpected">unexpected</A></B>();bool <B><A HREF="#uncaught_exception">uncaught_exception</A></B>(); // END OF DECLARATIONS</PRE><H2><A NAME="bad_exception"><CODE>bad_exception</CODE></A></H2><PRE>class <B>bad_exception</B> : public <A HREF="#exception">exception</A> { };</PRE><P>The class describes an exception that can be thrown from an<A HREF="#unexpected handler">unexpected handler</A>.The value returned by<CODE><A HREF="#exception::what">what</A>()</CODE>is an implementation-defined<A HREF="lib_over.html#C string">C string</A>.None of the member functions throw any exceptions.</P><H2><A NAME="exception"><CODE>exception</CODE></A></H2><PRE>class <B>exception</B> {public: <B>exception</B>() throw(); <B>exception</B>(const exception& right) throw(); exception& <B>operator=</B>(const exception& right) throw(); virtual <B>~exception</B>() throw(); virtual const char *<B>what</B>() const throw(); };</PRE><P>The class serves as the base class for all exceptions thrownby certain expressions and by the Standard C++ library. The<A HREF="lib_over.html#C string">C string</A> value returned by<B><CODE><A NAME="exception::what">what</A>()</CODE></B>is left unspecified by the default constructor,but may be defined by the constructors for certain derived classesas an implementation-defined<A HREF="lib_over.html#C string">C string</A>.</P><P>None of the member functions throw any exceptions.</P><H2><A NAME="set_terminate"><CODE>set_terminate</CODE></A></H2><PRE>terminate_handler <B>set_terminate</B>(terminate_handler pnew) throw();</PRE><P>The function establishes a new<A HREF="#terminate handler">terminate handler</A>as the function <CODE>*pnew</CODE>. Thus, <CODE>pnew</CODE> mustnot be a null pointer. The function returns the address of theprevious terminate handler.</P><H2><A NAME="set_unexpected"><CODE>set_unexpected</CODE></A></H2><PRE>unexpected_handler <B>set_unexpected</B>(unexpected_handler pnew) throw();</PRE><P>The function establishes a new<A HREF="#unexpected handler">unexpected handler</A>as the function <CODE>*pnew</CODE>. Thus, <CODE>pnew</CODE> mustnot be a null pointer. The function returns the address of theprevious unexpected handler.</P><H2><A NAME="terminate"><CODE>terminate</CODE></A></H2><PRE>void <B>terminate</B>();</PRE><P>The function calls a<B><A NAME="terminate handler">terminate handler</A></B>,a function of type <CODE>void ()</CODE>.If <CODE>terminate</CODE> is called directly by the program,the terminate handler is the one most recently set by a call to<CODE><A HREF="#set_terminate">set_terminate</A></CODE>.If <CODE>terminate</CODE> is called for any of several otherreasons during evaluation of a throw expression,the terminate handler is the one in effect immediately afterevaluating the throw expression.</P><P>A terminate handler may not return to its caller. At<A HREF="lib_over.html#program startup">program startup</A>,the terminate handler is a function that calls<CODE><A HREF="stdlib.html#abort">abort</A>()</CODE>.</P><H2><A NAME="terminate_handler"><CODE>terminate_handler</CODE></A></H2><PRE>typedef void (*<B>terminate_handler</B>)();</PRE><P>The type describes a pointer to a function suitable for use as a<A HREF="#terminate handler">terminate handler</A>.</P><H2><A NAME="uncaught_exception"><CODE>uncaught_exception</CODE></A></H2><PRE>bool <B>uncaught_exception</B>();</PRE><P>The function returns true only if a thrown exception is being currentlyprocessed. Specifically, it returns true after completing evaluation of athrow expression and before completing initialization of the exceptiondeclaration in the matching handler or calling<CODE><A HREF="#unexpected">unexpected</A></CODE> as a result of thethrow expression.</P><H2><A NAME="unexpected"><CODE>unexpected</CODE></A></H2><PRE>void <B>unexpected</B>();</PRE><P>The function calls an<B><A NAME="unexpected handler">unexpected handler</A></B>,a function of type <CODE>void ()</CODE>.If <CODE>unexpected</CODE> is called directly by the program,the unexpected handler is the one most recently set by a call to<CODE><A HREF="#set_unexpected">set_unexpected</A></CODE>.If <CODE>unexpected</CODE> is called when controlleaves a function by a thrown exception of a type not permitted by an<B><A NAME="exception specification">exception specification</A></B>for the function, as in:</P><PRE>void func() throw() // function may throw no exceptions {throw "bad"; } // throw calls unexpected()</PRE><P>the unexpected handler is the one in effect immediately afterevaluating the throw expression.</P><P>An unexpected handler may not return to its caller. It mayterminate execution by:</P><UL><LI>throwing an object of a type listed in the exception specification(or an object of any type if the unexpected handler is called directlyby the program)</LI><LI>throwing an object of type<A HREF="#bad_exception"><CODE>bad_exception</CODE></A></LI><LI>calling<CODE><A HREF="#terminate">terminate</A>()</CODE>,<CODE><A HREF="stdlib.html#abort">abort</A>()</CODE>, or<CODE><A HREF="stdlib.html#exit">exit</A>(int)</CODE></LI></UL><P>At <A HREF="lib_over.html#program startup">program startup</A>,the unexpected handler is a function that calls<CODE><A HREF="#terminate">terminate</A>()</CODE>.</P><H2><A NAME="unexpected_handler"><CODE>unexpected_handler</CODE></A></H2><PRE>typedef void (*<B>unexpected_handler</B>)();</PRE><P>The type describes a pointer to a function suitable for use as an<A HREF="#unexpected handler">unexpected handler</A>.</P><HR><P>See also the<B><A HREF="index.html#Table of Contents">Table of Contents</A></B> and the<B><A HREF="_index.html">Index</A></B>.</P><P><I><A HREF="crit_pjp.html">Copyright</A> © 1992-2002by P.J. Plauger. All rights reserved.</I></P><!--V4.01:1125--></BODY></HTML>⌨️ 快捷键说明
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