visual studio header file

[Wu zhen hai]

I read vs head file found something, who can illustrate them with simple language, I do not understand their funtion.

 #pragma pack(push,_CRT_PACKING)
 #pragma warning(push,3)
 #pragma push_macro("new")
 #undef new

 #pragma warning(disable: 4522 4800)
//....

 #pragma pop_macro("new")
 #pragma warning(pop)
 #pragma pack(pop) 

[helios]

1. Save the current packing behavior on a stack and set it to _CRT_PACKING.
2. Save the current warning level on a stack and set it to level 3.
3. Save the current value of macro new on a stack.
4. Undefine new.
6. Disable warnings.
9. Restore macro new and pop the stack.
10. Restore warning level and pop the stack.
11. Restore packing behavior and pop the stack.

Note that there's three separate stacks at work, here.