Question

Possible Duplicate:
What does “(void) new” mean in C++?

I’m not familiar with C++ and I don’t understand the line right after the method signature:

int EAN13Reader::decodeMiddle(Ref<BitArray> row,
        int startGuardBegin,
        int startGuardEnd,
        std::string& resultString)
{
    (void)startGuardBegin;
    ...
}

What’s (void)startGuardBegin;? A method invokation?

Answer 1

It tells the compiler that the argument is unused and thus it shouldn’t show an “unused argument” warning.

While compilers such as GCC usually have other ways (int startGuardBegin __attribute__ ((unused))) to indicated this, usually somehow in the function header, casting it to (void) does not rely on any compiler-specific features.