是否可以使用std :: nothrow参数进行放置新操作？

Question

I have a use case where I want to use placement new but also want to ensure that the new operation won't throw.

I figure I'd want something like the below (note this doesn't compile) but I wasn't sure how exactly to do it.

char buf1[100];                                                                                                           
Foo* foo = new (std::nothrow) (buf1) Foo(100);

Answer 1

There is no need to use std::nothrow in a placement new expression. unlike new / new[] , placement new / new[] are already defined as being noexcept .

[new.delete.placement]

 [[nodiscard]] void* operator new(std::size_t size, void* ptr) noexcept; [[nodiscard]] void* operator new[](std::size_t size, void* ptr) noexcept; 

If you look in [new.delete.single] and [new.delete.array] you'll see that the placement version will call the corresponding std::nothrow versions of new / new[] .