Multiple purposes depending on what you cast
- Marking your intention to the compiler that an expression that is entirely a no-op is intended as written (for inhibiting warnings, for example)
- Marking your intention to to the compiler and programmer that the result of something is ignored (the result of a function call, for example)
- In a function template, if a return type is given by a template parameter type
T, and you return the result of some function call that could be different from T in some situation. An explicit cast to T could, in the void case, prevent a compile time error:
int f() { return 0; } void g() { return (void)f(); }
- Inhibiting the compiler to choose a comma operator overload (
(void)a, b will never invoke an overloaded comma operator function).
Note that the Standard guarantees that there will never be an operator void() called if you cast a class object to void (some GCC versions ignore that rule, though).
