C++中的set_new_handler函数
首先，namespace std中有如下定义：
Typedef void (*new_handler)();
new_handler set_new_handler(new_handler new_p) throw();//C++98
new_handler set_new_handler (new_handler new_p) noexcept;//C++11
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译文开始：对于函数set_new_handler
函数说明
1. set_new_handler函数的作用是设置new_p指向的函数为new操作或new[]操作失败时调用的处理函数。
2. 设置的处理函数可以尝试使更多空间变为可分配状态，这样新一次的new操作就可能成功。当且仅当该函数成功获得更多可用空间它才会返回；否则它将抛出bad_alloc异常（或者继承该异常的子类）或者终止程序（例如调用abort或exit）。
3. 如果设置的处理函数返回了（例如，该函数成功获得了更多的可用空间）,它可能将被反复调用，直到内存分配成功，或者它不再返回，或者被其它函数所替代。
4. 在尚未用set_new_handler设置处理函数，或者设置的处理函数为空时，将调用默认的处理函数，该函数在内存分配失败时抛出bad_alloc异常。
参数说明
new_p:该函数指针所指的函数应为空参数列表且返回值类型为void
该函数可以尝试获得更多的可用空间，或者抛出异常，或者终止程序。
如果是一个空指针，处理函数将被重置为默认值（将会执行抛出bad_alloc异常）。
返回值
返回先前被设置的处理函数指针；如果尚未被设置或者已被重置，将返回空指针。
返回的函数指针是无参的void返回值类型的函数指针。
下面是一个简单的示例程序：
// new_handler example
#include <iostream> // std::cout
#include <cstdlib> // std::exit
#include <new> // std::set_new_handler
void no_memory () {
std::cout << "Failed to allocate memory!\n";
std::exit (1);
}
int main () {
std::set_new_handler(no_memory);
std::cout << "Attempting to allocate 1 GiB...";
char* p = new char [1024*1024*1024];
std::cout << "Ok\n";
delete[] p;
return 0;
}
new操作分配内存失败时将调用no_memory函数。
数据争用：
调用此函数不会引入数据竞争，任何这样的调用将会和随后set_new_handler和set_new_handler的调用同步。
注意，此要求仅适用于set_new_handler函数，但对于作为参数（new_p）传递的新处理函数却非必须。
异常安全：
无异常抛出保证：该函数（set_new_handler）不会抛出异常。
注意，如果new_p是没有实现适当功能的函数指针（见上面的参数说明），或者如果new_p是无效的指针，它会导致未定义的行为。
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原文如下：
Set new handler function
Sets new_p as the new-handlerfunction.
The new-handler function is a function which is called by thedefault allocation functions (operatornew and operatornew[]) when they fail to allocate storage.
The new-handler function may try to make more storageavailable for a new attempt to allocate the storage. If -and only if- thefunction succeeds in making more storage available, it may return. Otherwise itshall either throw a bad_allocexception (or a derived class) orterminate the program (such as by calling abort or exit).
If the new-handler function returns (i.e., it made morestorage available), it may be called repeatedly for as long as theallocationfunction fails to allocate the requested storage, or until the new-handlerfunction does not return or is replaced.
Before this function is called by the program for the first time, or if new_p isa null-pointer, the default allocation functions directlythrow bad_alloc on failure.
Parameters
new_p
Functionthat takes no arguments and returns no value (void).
The function can make more storage available, or throw an exception, orterminate the program.
If this is a null-pointer, the new-handler function isreset to none (and bad_alloc is thrown instead).
new_handler isa function pointer type for functions that take no arguments and return novalue.
Return value
The value ofthe current new-handler function if this has already been setby this function previously, or a null-pointer if this is thefirst call to set_new_handler (or if it was reset by a previouscall).
new_handler isa function pointer type taking no arguments and returning no value.
Data races
Calling this function does notintroduce data races, and any such call is synchronized with subsequent callstoset_new_handler and get_new_handler.
Notice that this requirement applies only to the set_new_handler function,but not necessarily to the new-handler functionpassed as argument (new_p).
Exception safety
No-throwguarantee: this function (set_new_handler) never throwsexceptions.
Notice that if new_p is a function that does not implement theproper functionality (described above), or if new_p is aninvalid pointer, it causes undefined behavior.