I have been told that "new-expression will call
operator new is part of the standard. The implementation is required to supply the operator at the global scope in each translation unit in your program. From [basic.stc.dynamic]/2
The library provides default definitions for the global allocation and deallocation functions. Some global allocation and deallocation functions are replaceable (18.6.1). A C++ program shall provide at most one definition of a replaceable allocation or deallocation function. Any such function definition replaces the default version provided in the library (188.8.131.52). The following allocation and deallocation functions (18.6) are implicitly declared in global scope in each translation unit of a program.
void* operator new(std::size_t); void* operator new(std::size_t); void operator delete(void*); void operator delete(void*); void operator delete(void*, std::size_t) noexcept; void operator delete(void*, std::size_t) noexcept;
This is why you do not need to include anything to use