I am reading a document given to me by a professor and I'm trying to understand the following line of code.
C *r = new(p) C[3];
what exactly is the code doing? What does the C[3] after the new(p) accomplish?
This line of code constructs an array of 3 items of type C, similar to this, which is hopefully more familiar to you:
C *r = new C[3];
The primary difference is that new(p) does not allocate new memory; instead it constructs the array in a pre-existing memory buffer pointed by p. For example:
char *p = new char[3*sizeof(C)];
C *r = new(p) C[3];
Another difference is that you can't use delete[] to call the deconstructors and free the memory. You have to call the deconstructors manually
for (int i=0; i<3: i++) r->~C();
delete[] p;
See also What uses are there for "placement new"? and Wikipedia.
Collected from the Internet
Please contact [email protected] to delete if infringement.
Comments