C++ new的nothrow关键字和new_handler用法
new && new(std::nothrow)
new(std::nothrow) 顾名思义，即不抛出异常，当new一个对象失败时，默认设置该对象为NULL，这样可以方便的通过if(p == NULL) 来判断new操作是否成功
普通的new操作，如果分配内存失败则会抛出异常，虽然后面一般也会写上if(p == NULL) 但是实际上是自欺欺人，因为如果分配成功，p肯定不为NULL；而如果分配失败，则程序会抛出异常，if语句根本执行不到。
因此，建议在c++代码中，凡是涉及到new操作，都采用new(std::nothrow)，然后if(p==NULL)的方式进行判断
#include <new>
#include <iostream>
#include <stdlib.h>
#include <stdio.h>
using namespace std;
//void __cdecl newhandler()
//{
// printf(".....%20s,%10d,,,,,,,
", __FUNCTION__, __LINE__);
// return;
//}
int main()
{
// set_new_handler(newhandler);
char *p = new char[0x2000000];
if(NULL == p)
{
//记录日志
printf(".....%20s,%10d,,,,,,,
", __FUNCTION__, __LINE__);
return false;
}
printf(".....%20s,%10d, p=0x%10x,,,,,,,
", __FUNCTION__, __LINE__, p);
return 0;
}
不做任何处理，抛出异常：
[root@dvrdvs nfs] # ./a.out terminate calleda.out/636: potentially unexpected fatal signal 6. after throwing an instance of ' Pid: 636, comm: a.out what(): std:CPU: 0 Tainted: P (3.0.8 #1-svn16375) :bad_alloc PC is at 0x40253a98 LR is at 0x40253a44 pc : [<40253a98>] lr : [<40253a44>] psr: 60000010 sp : bef34bb0 ip : 4029615c fp : bef34c6c r10: 008ae1d8 r9 : 00000000 r8 : 401ca704 r7 : 0000010c r6 : 40296394 r5 : 00000006 r4 : 0000027c r3 : 40296144 r2 : 00000006 r1 : 0000027c r0 : 00000000 Flags: nZCv IRQs on FIQs on Mode USER_32 ISA ARM Segment user Control: 0005317f Table: 824bc000 DAC: 00000015 [<c002dd4c>] (show_regs+0x0/0x50) from [<c0055e08>] (get_signal_to_deliver+0x35c/0x384) r4:020c0027 r3:0000000a [<c0055aac>] (get_signal_to_deliver+0x0/0x384) from [<c002eb70>] (do_signal+0x70/0x56c) [<c002eb00>] (do_signal+0x0/0x56c) from [<c002f0c0>] (do_notify_resume+0x54/0x60) [<c002f06c>] (do_notify_resume+0x0/0x60) from [<c002c194>] (work_pending+0x24/0x28) r4:0000027c r3:20000013 Aborted
若设置了set_new_handler，则会进入到死循环