[Bug c/108476] Please turn -Wreturn-type on by default for C

["alexhenrie24 at gmail dot com" <gcc-bugzilla@gcc.gnu.org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=108476

--- Comment #3 from Alex Henrie <alexhenrie24 at gmail dot com> ---
(In reply to Andrew Pinski from comment #1)
> Note the warning should really be split into two different options. One for
> the return type of the declaration and one for the missing return in
> non-void case.
That would be nice, I agree. I'd just like to note that since the warning
should occur by default in both situations, this feature request does not
depend on splitting the warning in two.

(In reply to Jakub Jelinek from comment #2)
> The reason it is enabled by default for C++ is that the 2 languages differ
> significantly in this regard.  Falling through the end of a non-void
> function in C++ is undefined behavior, in C it is not, in C it is only UB if
> the caller actually uses the uninitialized return value (which is much
> harder to warn about).
Yes, I did read the note about that in the documentation (although I didn't
quote that part in comment #0). You're right that it's slightly less bad in C
because not specifying the return value is immediately undefined behavior in
C++, whereas in C it only becomes undefined behavior once the return value is
used. However, few people know about that subtle difference between C and C++
(which leads to a false sense of security when the warning does not appear in
C), and not specifying the return value will almost certainly lead to undefined
behavior in C even though technically there are situations where it does not.

> And in C it is enabled in -Wall, which you should use anyway if you care
> about warnings.
I do use -Wall whenever I can. Unfortunately, not everyone does (particularly
novices or people stuck with awful embedded-toolchain IDEs that don't make it
easy to change compiler settings), so I'd like the default to be both less
confusing and more protective against likely undefined behavior.