Re: Verify and expression

Andrei Alexandrescu (See Website For Email) posted:


The original code contained such a variable, so I took the liberty of
presuming it had a purpose. There's not much merit in writing "assert
(false)", as your error message will simply describe the error as "false"
rather than "start_bus()".

Essentially, I think the OP wants a function/macro that works exactly like
assert, except that it still evaluates its argument when in Release Mode.
Furthermore, I think the OP wants to retain the value of the expression. The
following might be a start:

#include <iostream>
#include <ostream>
#include <cstdlib>

template<class T>
T const &Verify(T const &expr,char const *const str)
{
    if(!expr)
    {
        std::cerr << "VERIFY Failure. \"" __FILE__ "\": Line "
                  << __LINE__ << " -- " << str << std::endl;

        exit(EXIT_FAILURE);
    }

    return expr;
}

template<class T>
T &Verify(T &expr,char const *const str)
{
    return const_cast<T&>(
        Verify(const_cast<T const&>(expr),str)
        );
}

#define VERIFY(expr) (Verify((expr),#expr))

class MyClass {
public:

    MyClass() {}

    operator double() const { return 56.8; }

    operator bool() const { return false; }

};

int main()
{
    MyClass obj;

    double val = VERIFY(obj);

    MyClass &r = VERIFY(obj);

    std::cout << val << std::endl;
}

--

Frederick Gotham

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