关于operator new重载和异常的问题
为什么这个代码片段会输出很多“here”？
我认为程序应该在调用 throw std::invalid_argument( "fool" ); 后终止。
#include <memory>
#include <iostream>
void* operator new(std::size_t size)
{
std::cout << "here" << std::endl;
throw std::invalid_argument( "fool" ); //commit out this, there would be many many ouputs
return std::malloc(size);
}
void operator delete(void* ptr)
{
return free(ptr);
}
int main()
{
//std::unique_ptr<int> point2int(new int(999));
int* rawpoint2int = new int(666);
}
Why this code snippet ouputs a lot of "here"?
I think the program should terminate when after throw std::invalid_argument( "fool" ); has been called.
#include <memory>
#include <iostream>
void* operator new(std::size_t size)
{
std::cout << "here" << std::endl;
throw std::invalid_argument( "fool" ); //commit out this, there would be many many ouputs
return std::malloc(size);
}
void operator delete(void* ptr)
{
return free(ptr);
}
int main()
{
//std::unique_ptr<int> point2int(new int(999));
int* rawpoint2int = new int(666);
}
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std::invalid_argument的 文档 包含线索：您可以看到字符串参数是按设计复制的。这意味着如果您以这种方式抛出此异常，则几乎可以保证重新输入
new。您还应该注意，
malloc可以返回nullptr，这将违反operator new的设计，该设计应返回有效指针或抛出异常。在这种情况下抛出的正常异常类型是 std::bad_alloc。我无法想象你为什么要抛出
std::invalid_argument。我想您可能在某个构造函数中遇到了这个问题，并决定测试分配本身。从技术上讲，您可以通过传递默认构造的字符串作为参数来解决该问题：
Eww，yucky。我建议您找到一个更合适的异常来抛出（如果您确实需要一个异常），或者创建您自己的非分配异常。
The documentation for
std::invalid_argumentholds the clue:You can see that the string argument is copied by design. This means that re-entering
newis pretty much guaranteed if you are throwing this exception in this way.You should also be aware that
malloccan returnnullptrwhich will violate the design ofoperator newwhich should either return a valid pointer or throw.The normal kind of exception to throw in this case is
std::bad_alloc. I cannot imagine why you are wanting to throwstd::invalid_argument. I thought perhaps you were encountering this issue in a constructor somewhere and decided to test the allocation itself.Technically you can resolve the problem by passing a default-constructed string as the argument:
Eww, yucky. I recommend you find a more appropriate exception to throw (if you actually need one), or create your own non-allocating exception.