force to check return value

#ifndef NDEBUG
#include

template
class CheckReturnML
{
public:

    CheckReturnML(const T& value) :
        value(value), check(true){}

    ~CheckReturnML()
    {
        if(check)
            assert("must check return value" == nullptr);
    }

    operator T(void)
    {
        check = false;

        return value;
    }

private:
    T value;
    mutable bool check;
};

#define CRML(x) using x##c = CheckReturnML; \
                using u##x##c = CheckReturnML;
CRML(char)
CRML(short)
CRML(int)
CRML(long)
using longlongc = CheckReturnML;
using ulonglongc = CheckReturnML;

#else // !NDEBUG

#define CRML(x) using x##c = x; \
                using u##x##c = unsigned x;
CRML(char)
CRML(short)
CRML(int)
CRML(long)
using longlongc = long long;
using ulonglongc = unsigned long long;

#endif // !!NDEBUG
 

不能在编译时check，runtime check不太完美。