Need to generate unique keys for the class data members. Hence I am thinking of getting the difference between the address of the variable minus the address of the class object. For example:
struct X {
int i; // &i - &X() = 0 (GCC)
double d; // &d - &X() = 8 (GCC)
};
This is a one time exercise and hence will be happening in very beginning of the code execution for all the interested classes. So typically I will be declaring a dummy object of the class and finding the address difference by typecasting. Such as:
X x;
keyOf_i = long(&x.i) - long(&x);
keyOf_d = long(&x.d) - long(&x);
Is there any better way?
Assume that the access specifier (private
) are not the problem.
Will be also interested, if someone has got any other approach to generate unique keys for class data variables apart from this way.
Update: With using offseof()
macro, I am getting following warning in G++-6:
offsetof within non-standard-layout type ‘MyClass’ is undefined
Actually I have some string & other class variables as well inside MyClass
. I am fine, even if this undefined thing gives unique address whatsoever. However, would like to get more information of offsetof()
and other alternatives.
How about using offsetof() macro for this. Check http://man7.org/linux/man-pages/man3/offsetof.3.html for more details.
Sample code below from the man page: