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<HTML><HEAD><TITLE><new></TITLE></HEAD><BODY><H1><A NAME="<new>"><CODE><new></CODE></A></H1><HR><P>Include the standard header <B><CODE><new></CODE></B>to define several types and functions that control allocation andfreeing of storage under program control.</P><P>Some of the functions declared in this header are<B><A NAME="replaceable functions">replaceable</A></B>.The implementation supplies a default version, whose behavior isdescribed in this document. A program can, however, define afunction with the same signature to replace the default versionat link time. The replacement version must satisfy the requirementsdescribed in this document.</P><PRE>namespace std {typedef void (*<B><A HREF="#new_handler">new_handler</A></B>)();class <B><A HREF="#bad_alloc">bad_alloc</A></B>;class <B><A HREF="#nothrow_t">nothrow_t</A></B>;extern const nothrow_t <B><A HREF="#nothrow">nothrow</A></B>; // FUNCTIONSnew_handler <B><A HREF="#set_new_handler">set_new_handler</A></B>(new_handler pnew) throw(); }; // OPERATORS -- NOT IN NAMESPACE stdvoid <B><A HREF="#operator delete">operator delete</A></B>(void *ptr) throw(); // REPLACEABLEvoid <B><A HREF="#operator delete">operator delete</A></B>(void *, void *) throw();void <B><A HREF="#operator delete">operator delete</A></B>(void *ptr, // REPLACEABLE const std::nothrow_t&) throw();void <B><A HREF="#operator delete[]">operator delete[]</A></B>(void *ptr) throw(); // REPLACEABLEvoid <B><A HREF="#operator delete[]">operator delete[]</A></B>(void *, void *) throw();void <B><A HREF="#operator delete[]">operator delete[]</A></B>(void *ptr, // REPLACEABLE const std::nothrow_t&) throw();void *<B><A HREF="#operator new">operator new</A></B>(std::size_t count) // REPLACEABLE throw(std::bad_alloc);void *<B><A HREF="#operator new">operator new</A></B>(std::size_t count, // REPLACEABLE const std::nothrow_t&) throw();void *<B><A HREF="#operator new">operator new</A></B>(std::size_t count, void *ptr) throw();void *<B><A HREF="#operator new[]">operator new[]</A></B>(std::size_t count) // REPLACEABLE throw(std::bad_alloc);void *<B><A HREF="#operator new[]">operator new[]</A></B>(std::size_t count, // REPLACEABLE const std::nothrow_t&) throw();void *<B><A HREF="#operator new[]">operator new[]</A></B>(std::size_t count, void *ptr) throw();</PRE><H2><A NAME="bad_alloc"><CODE>bad_alloc</CODE></A></H2><PRE>class <B>bad_alloc</B> : public <A HREF="exceptio.html#exception">exception</A> { };</PRE><P>The class describes an exception thrown to indicate thatan allocation request did not succeed. The value returned by<CODE><A HREF="exceptio.html#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="new_handler"><CODE>new_handler</CODE></A></H2><PRE>typedef void (*<B>new_handler</B>)();</PRE><P>The type describes a pointer object thatdesignates a function suitable for use as a<A HREF="#new handler">new handler</A>.</P><H2><A NAME="nothrow"><CODE>nothrow</CODE></A></H2><PRE>extern const nothrow_t <B>nothrow</B>;</PRE><P>The object is used as a function argument tomatch the parameter type<CODE><A HREF="#nothrow_t">nothrow_t</A></CODE>.</P><H2><A NAME="nothrow_t"><CODE>nothrow_t</CODE></A></H2><PRE>class <B>nothrow_t</B> {};</PRE><P>The class is used as a function parameter to<CODE>operator new</CODE> to indicate that the function shouldreturn a null pointer to report an allocation failure,rather than throw an exception.</P><H2><A NAME="operator delete"><CODE>operator delete</CODE></A></H2><PRE>void <B>operator delete</B>(void *ptr) throw(); // REPLACEABLEvoid <B>operator delete</B>(void *, void *) throw();void <B>operator delete</B>(void *ptr, // REPLACEABLE const std::nothrow_t&) throw();</PRE><P>The first function is called by a<B><A NAME="delete expression"><CODE>delete</CODE> expression</A></B>to render the value of <CODE>ptr</CODE> invalid.The program can define a function with this function signature that<A HREF="#replaceable functions">replaces</A>the default version defined by theStandard C++ library. The required behavior is to accept a value of<CODE>ptr</CODE> that is null or that was returned by an earlier call to<CODE><A HREF="#operator new">operator new</A>(size_t)</CODE>.</P><P>The default behavior for a null value of <CODE>ptr</CODE> isto do nothing. Any other value of <CODE>ptr</CODE> must be a value returnedearlier by a call as described above.The default behavior for such a non-null value of <CODE>ptr</CODE> is toreclaim storage allocated by the earlier call.It is unspecified under what conditions part or allof such reclaimed storage is allocated by a subsequent call to<CODE><A HREF="#operator new">operator new</A>(size_t)</CODE>,or to any of<CODE><A HREF="stdlib.html#calloc">calloc</A>(size_t)</CODE>,<CODE><A HREF="stdlib.html#malloc">malloc</A>(size_t)</CODE>, or<CODE><A HREF="stdlib.html#realloc">realloc</A>(void*, size_t)</CODE>.</P><P>The second function is called by a<B><A NAME="placement delete expression">placement<CODE>delete</CODE> expression</A></B> corresponding to a<A HREF="#new expression"><CODE>new</CODE> expression</A>of the form<CODE>new(std::size_t)</CODE>.It does nothing.</P><P>The third function is called by a placement<CODE>delete</CODE> expression corresponding to a<CODE>new</CODE> expression of the form<CODE>new(std::size_t, const std::nothrow_t&)</CODE>.The program can define a function with this function signature that<A HREF="#replaceable functions">replaces</A>the default version defined by theStandard C++ library. The required behavior is to accept a value of<CODE>ptr</CODE> that is null or that was returned by an earlier call to<CODE><A HREF="#operator new">operator new</A>(size_t)</CODE>.The default behavior is to evaluate <CODE>delete(ptr)</CODE>.</P><H2><A NAME="operator delete[]"><CODE>operator delete[]</CODE></A></H2><PRE>void <B>operator delete[]</B>(void *ptr) throw(); // REPLACEABLEvoid <B>operator delete[]</B>(void *, void *) throw();void <B>operator delete[]</B>(void *ptr, // REPLACEABLE const std::nothrow_t&) throw();</PRE><P>The first function is called by a<B><A NAME="delete[] expression"><CODE>delete[]</CODE> expression</A></B>to render the value of <CODE>ptr</CODE> invalid.The program can define a function with this function signature that<A HREF="#replaceable functions">replaces</A>the default version defined by theStandard C++ library.</P><P>The required behavior is to accept a value of <CODE>ptr</CODE>that is null or that was returned by an earlier call to<CODE><A HREF="#operator new[]">operator new[]</A>(size_t)</CODE>.The default behavior is to evaluate <CODE>delete(ptr)</CODE>.</P><P>The second function is called by a<B><A NAME="placement delete[] expression">placement<CODE>delete[]</CODE> expression</A></B> corresponding to a<A HREF="#new[] expression"><CODE>new[]</CODE> expression</A> of the form<CODE>new[](std::size_t)</CODE>.It does nothing.</P><P>The third function is called by a placement<CODE>delete</CODE> expression corresponding to a<CODE>new[]</CODE> expression of the form<CODE>new[](std::size_t, const std::nothrow_t&)</CODE>.The program can define a function with this function signature that<A HREF="#replaceable functions">replaces</A>the default version defined by theStandard C++ library. The required behavior is to accept a value of<CODE>ptr</CODE> that is null or that was returned by an earlier call to<CODE><A HREF="#operator new[]">operator new[]</A>(size_t)</CODE>.The default behavior is to call<CODE>operator delete(ptr, std::nothrow)</CODE>.</P><H2><A NAME="operator new"><CODE>operator new</CODE></A></H2><PRE>void *<B>operator new</B>(std::size_t count) throw(bad_alloc); // REPLACEABLEvoid *<B>operator new</B>(std::size_t count, // REPLACEABLE const std::nothrow_t&) throw();void *<B>operator new</B>(std::size_t count, void *ptr) throw();</PRE><P>The first function is called by a<B><A NAME="new expression"><CODE>new</CODE> expression</A></B>to allocate <CODE>count</CODE> bytes of storagesuitably aligned to represent any object of that size.The program can define a function with this function signature that<A HREF="#replaceable functions">replaces</A>the default version defined by the Standard C++ library.</P><P>The required behavior is to return a non-null pointer onlyif storage can be allocated as requested. Each such allocationyields a pointer to storage disjoint from any other allocated storage.The order and contiguity of storage allocated by successive callsis unspecified. The initial stored value is unspecified.The returned pointer designates the start (lowestbyte address) of the allocated storage. If <CODE>count</CODE> is zero, thevalue returned does not compare equal to any other value returnedby the function.</P><P>The default behavior is to execute a loop. Within the loop,the function first attempts to allocate the requested storage. Whetherthe attempt involves a call to<CODE><A HREF="stdlib.html#malloc">malloc</A>(size_t)</CODE>is unspecified. If the attempt is successful, the function returnsa pointer to the allocated storage.Otherwise, the function calls the designated<A HREF="#new handler">new handler</A>. If thecalled function returns, the loop repeats. The loop terminates whenan attempt to allocate the requested storage is successful or whena called function does not return.</P><P>The required behavior of a<B><A NAME="new handler">new handler</A></B>is to perform one of the following operations:</P><UL><LI>make more storage available for allocation and then return</LI><LI>call either<CODE><A HREF="stdlib.html#abort">abort</A>()</CODE> or<CODE><A HREF="stdlib.html#exit">exit</A>(int)</CODE></LI><LI>throw an object of type<A HREF="#bad_alloc"><CODE>bad_alloc</CODE></A></LI></UL><P>The default behavior of a<A HREF="#new handler">new handler</A> is to throw an object of type<CODE>bad_alloc</CODE>. A null pointer designates the defaultnew handler.</P><P>The order and contiguity of storage allocated by successivecalls to <CODE>operator new(size_t)</CODE> is unspecified,as are the initial values stored there.</P><P>The second function:</P><PRE>void *<B>operator new</B>(std::size_t count, const std::nothrow_t&) throw();</PRE><P>is called by a<A HREF="#placement new expression">placement<CODE>new</CODE> expression</A>to allocate <CODE>count</CODE> bytes of storagesuitably aligned to represent any object of that size.The program can define a function with this function signature that<A HREF="#replaceable functions">replaces</A>the default version defined by the Standard C++ library.<P>The default behavior is to return<CODE>operator new(count)</CODE> if thatfunction succeeds. Otherwise, it returns a null pointer.</P><P>The third function:</P><PRE>void *<B>operator new</B>(std::size_t count, void *ptr) throw();</PRE><P>is called by a<B><A NAME="placement new expression">placement <CODE>new</CODE> expression</A></B>,of the form <CODE>new (args) T</CODE>.Here, <CODE>args</CODE> consists of a single object pointer.The function returns <CODE>ptr</CODE>.</P><H2><A NAME="operator new[]"><CODE>operator new[]</CODE></A></H2><PRE>void *<B>operator new[]</B>(std::size_t count) // REPLACEABLE throw(std::bad_alloc);void *<B>operator new[]</B>(std::size_t count, // REPLACEABLE const std::nothrow_t&) throw();void *<B>operator new[]</B>(std::size_t count, void *ptr) throw();</PRE><P>The first function is called by a<B><A NAME="new[] expression"><CODE>new[]</CODE> expression</A></B>to allocate <CODE>count</CODE> bytes of storagesuitably aligned to represent any array object ofthat size or smaller. The program can define a functionwith this function signature that<A HREF="#replaceable functions">replaces</A>the default version defined by the Standard C++ library.</P><P>The required behavior is the same as for<CODE><A HREF="#operator new">operator new</A>(size_t)</CODE>.The default behavior is to return<CODE><A HREF="#operator new">operator new</A>(count)</CODE>.</P><P>The second function is called by a<A HREF="#placement new[] expression">placement<CODE>new[]</CODE> expression</A>to allocate <CODE>count</CODE> bytes of storagesuitably aligned to represent any array object of that size.The program can define a function with this function signature that<A HREF="#replaceable functions">replaces</A>the default version defined by the Standard C++ library.<P>The default behavior is to return<CODE>operator new(count)</CODE> if thatfunction succeeds. Otherwise, it returns a null pointer.</P><P>The third function is called by a<B><A NAME="placement new[] expression">placement<CODE>new[]</CODE> expression</A></B>,of the form <CODE>new (args) T[N]</CODE>.Here, <CODE>args</CODE> consists of a single object pointer.The function returns <CODE>ptr</CODE>.</P><H2><A NAME="set_new_handler"><CODE>set_new_handler</CODE></A></H2><PRE>new_handler <B>set_new_handler</B>(new_handler pnew) throw();</PRE><P>The function stores <CODE>pnew</CODE> in a static<A HREF="#new handler">new handler</A> pointerthat it maintains, then returns the value previouslystored in the pointer. The new handler is used by<CODE><A HREF="#operator new">operator new</A>(size_t)</CODE>.</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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