My Herb Schildt book on C++ says: \"... In C++, if a function is declared as returning a value, it must return a value.\" However, if I write a function wit
Like the GMan said the only exception is the main function. I still see tons of books returning 0 in main which isn't really necessary. Oh well I guess it could be worse and you could be learning from a book that uses void main() instead of int main(). But I think what you should learn from all this is that your compiler is complaining for a reason and it's good you took note of it since it will usually save you headaches in the long run.
§6.6.3/2:
Flowing off the end of a function is equivalent to a return with no value; this results in undefined behavior in a value-returning function.
So it depends on your definition of mandatory. Do you have to? No. But if you want your program to have well-defined behavior, yes.*
*main
is an exception, see §3.6.1/5. If control reaches the end of main
without a return
, it will have the effect of return 0;
.
Is it mandatory? I don't believe so, however not returning a value in a non-void returning function is undefined as per my understanding of the c++ standards (except for main, which returns 0).
Does that mean it's OK? Probably not - if the function is supposed to return a value, you should be returning one, that could get real messy in complex code bases.
Yes, it must return a value.
Flowing off the end of a function is equivalent to a return with no value; this results in undefined behavior in a value-returning function.
This question will bring more light to the subject
It's not mandatory to have a return statement in a function declared as returning non-void and it doesn't have to lead to undefined behaviour.
Such a function could:
std::terminate
Of course, if a function avoids undefined behaviour by always doing one of the above it probably shouldn't be declared as returning non-void if possible.
One obvious case where it would need to is if it is a virtual function which for a particular point in a class hierarchy can't return a valid value and always exits via an exception.
Forgetting to include a return
statement in some control path of a value-returning function does not make your code ill-formed. I.e. you should normally expect the code to compile (maybe with a warning). In that sense it is not "mandatory".
However, actually flowing off the end of value-returning function in C++ is always undefined behavior. (In C it is undefined behavior only if the calling code actually uses the result.)