Question

I have a class A that I overload its operator=. However it is required that I need to do something like this:

volatile A x;
A y;
x = y;

which raised an error while compiling

error: no operator "=" matches these operands
       operand types are: volatile A = A

If I removed volatile, it’s compilable. Is there anyway to have this compiled without removing the “volatile” (and still keep the behavior of volatile) ?

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Basically this is a CUDA program in which ‘x’ is a shared memory ( all threads can access and modify its value ). I want it to be “volatile” in order to avoid the compiler optimization and re-use the value instead of accessing the memory address.

More on the problem: at the beginning A is just a primitive type e.g integer, volatile worked as expected and doesn’t cause any problem, now I want it to be a custom class ( integer 128-bit for example ). I’m not sure why C++ complain in this case but not with primitive data type.

Thanks in advance.

Answer 1

Assuming the volatile qualification is necessary, you’ll have to add a volatile assignment operator to A (A& A::operator=(const A&) volatile).

const_cast<A&>(x) = y will make it compile, but will technically cause undefined behaviour, and will certainly remove the guarantees that volatile gives.