Question

Possible Duplicate:
What is the purpose of the statement “(void)c;”?

class ArgString : public Arg::Base
{
public:
    ...
    bool CanConvertToInt() const
    {
        const char *cstr = mValue.c_str();
        char *result = 0;
        long d = strtol(cstr, &result, 10);
        (void) d; // what is the usage of this line?
        return result != cstr;
    }

private:
    std::string mValue;
};

Can someone tell me what the purpose of the following line is?

(void) d;

Thank you

// Update //

As some people pointed out, the purpose of the line is to suppress the compilation warning. To me, that is very strange. Because this is much severe warning

    warning C4996: 'sprintf': This function or variable may be unsafe. Consider using sprintf_s instead. To disable deprecation, use
_CRT_SECURE_NO_WARNINGS. See online help for details.

Why we ignore this big warning and ONLY address the smaller one.

Answer 1

The pattern (void)d is typically done to tell a code analyzer that you are explicitly ignoring the return value of a function. Many C analyzers consider it an error to ignore a return value as it could result in ignoring a failure. This is a way of saying “I meant to do that”