关于operator new 的问题

[KingI]

#include <iostream>
using namespace std;
#include <new>
#include <exception>

class A
{
double i;
public:
A(int n=0) : i(n) { }
static void * operator new [](size_t size) throw (bad_alloc &);
static void operator delete [](void *p);
};

void * A::operator new [](size_t size) throw (bad_alloc &)
{
void *mem;
/* try { //问题就在这里
mem=::operator new (size);
}catch(...) {
throw bad_alloc();
}
*/
mem=::operator new (size);
if (!mem)
throw bad_alloc();

return mem;
}

void A::operator delete [](void *p)
{
::operator delete (p);
}

void main()
{
A *a＝NULL;
try {
a=new A[500000000];
}catch(bad_alloc &err) {
cerr<<err.what()<<endl;
return ;
}

delete []a;
cout<<"Done!\n";
}

问题就在这个void * A::operator new [](size_t size) throw (bad_alloc &)函数中：
为什么用异常处理机制捕捉不到内存不足的异常，而用if(!mem）可以成功呢？
全局的operator new中应该会抛出异常吧？

[fireman_lh]

在effective c++中这里是把set_new_handler出去的globalhandler再重新加载回来的

[fireman_lh]

template<class t>
void * newhandlersupport<t>::operator new(size_t size)
{
new_handler globalhandler =
std::set_new_handler(currenthandler);
void *memory;
try {
memory = ::operator new(size);
}
catch (std::bad_alloc&) {
std::set_new_handler(globalhandler);
throw;
}

std::set_new_handler(globalhandler);
return memory;
}

[fireman_lh]

我一直有个问题想问的是，如果在这里不把globalhandler重载回去的话，系统的globalhandler会一直保持这个吗？

[KingI]

To：fireman_lh()
刚才试了一下，可是编译器报错：error C2039: 'set_new_handler' : is not a member of 'std'

[bugebear3]

一直对异常都不太清楚,向楼上的学习

[horris]

mark and help up