Question: I use a (C) library with functions taking different parameters but always returning an int greater than zero in case of error:

```
int functionA(int param1, char param2); /* return an error code on failure, 0 otherwise */
int functionB(LIB_BOOLEAN param1);      /* return an error code on failure, 0 otherwise */
// ...

```

I would like to turn them all to be exception ready:

```
if (functionA(param1, param2) > 0)
{ throw std::runtime_error("Method failed"); }

```

Is it possible to write a template to do it once for all method ?

EDIT:
The idea is to avoid checking the result for each functions every time I use them.

Answer: 
Here is a template-based solution using C++17's new `auto` template parameters:

```
template <auto &> struct CallerImpl;

template <typename ...Args, int (&F)(Args ...)>
struct CallerImpl<F>
{
    static int CallOrThrow(Args ... args)
    {
        if (int n = F(args...); n > 0)
            throw std::runtime_error("Method failed");
        else
            return n;
    }
};

template <auto & F, typename ... Brgs>
int CallOrThrow(Brgs ... brgs)
{
    return CallerImpl<F>::CallOrThrow(brgs...);
}

```

Usage example:

```
int foo(double, char)
{
    std::cout << "Foo called\n";
    return 8;
}

CallOrThrow<foo>(1.5, 'x');

```
Here’s one approach that doesn’t require changing call sites. Assuming these C functions all have the same convention for return codes, you can write a wrapper that converts the return code to an exception.

```
inline void checked(const char *name, int result) {
    if (result > 0)
        throw std::runtime_error(name);
}

```

Then introduce a preprocessor definition for each function.

```
#define functionA(...) checked("functionA", functionA(__VA_ARGS__))

```

This works because `functionA` will not be expanded within the definition of the `functionA` macro. And variadic macros are standard since C++11.