Assigning and Conditional Testing Simultaneously in C++

Question

I have three functions that return integer error codes, e.g.

int my_function_1(const int my_int_param);
int my_function_2(const int my_int_param);
int my_function_3(const int my_int_param);

I want to assign and test for error at the same time for brevity. Will the following work and be portable?

int error=0;
...
if ( error ||
     (error = my_function_1(val1) ||
      error = my_function_2(val2) ||
      error = my_function_3(val3)) ) {
   std::cout << "AN ERROR OCCURRED!!!" << std::endl;
}

Thanks!

Answer 1

error is initialized to 0.So the && will always evaluates to false. So other parts of the if condition are never evaluated. So this code will not work. If you remove the && condition the code should work portably as the standard guarantees the order of the evaluation in this case.

Answer 2

I don't understand why you have the error && at the beginning of the function, but the rest should do what you want. Short circuit evaluation of the || operators is guaranteed by the standard. I would consider it bad style though.

Edit: Based on your comment, you would need to replace error && with error ||. I will also add that this is a good reason to use exceptions rather than error codes, it makes your code so much easier to read.

Answer 3

Why not throw an exception?

void my_function_1(const int my_int_param);
void my_function_2(const int my_int_param);
void my_function_3(const int my_int_param);

try {
    my_function_1(...);
    my_function_2(...);
    my_function_3(...);
} catch(std::exception& e) {
    std::cout << "An error occurred! It is " << e.what() << "\n";
}

Answer 4

Yes, after the minor change of && with || it will work. But it's just too confusing (using = in tests is confusing) with not much benefit.

You could go for exception line another poster suggested, or simply put your checked code inside function and do like below.

int checked(){
    int error = 0;
    error = my_function_1(val1); if (error) return error;
    error = my_function_2(val1); if (error) return error;
    error = my_function_3(val1); if (error) return error;
    return error;
}

I believe any programmer will easily understand what is done here.