C++ new operator weird syntax

[leonardo1]

Hi,

I was reading the E Appendix of "The C++ Programming Language , Special Edition" when I came across on page 948 with the following syntax:
"new(b.space) T(x);" where b.space is a pointer and x an object of type T. Does this syntax works in modern C++ compilers?

Thank you

[laserlight]

Why not test and find out for yourself? Or if you want others to help you test, then post the smallest and simplest program that you expect to be compilable. Not everyone has a copy of TC++PL.

[Hermit]

This is called placement new, and basically it's for constructing objects at a particular (pre-allocated) memory address without allocating anything. In the TC++PL example, a copy of x will be constructed at the address pointed to by b.space.

[Lindley]

In any reasonably optimizing compiler, this is identical to

*b.space = T(x);


Assuming a copy constructor or operator= exists for the class. If x really is of type T, then I assume it does; in which case it's effectively the same as


*b.space = x;