[Bug target/113981] New: risc-v: non-void C++ function with no return statement has no ret

[Bug target/113981] New: risc-v: non-void C++ function with no return statement has no ret

[Simon.Richter at hogyros dot de]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=113981

            Bug ID: 113981
           Summary: risc-v: non-void C++ function with no return statement
                    has no ret
           Product: gcc
           Version: 14.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: target
          Assignee: unassigned at gcc dot gnu.org
          Reporter: Simon.Richter at hogyros dot de
  Target Milestone: ---

On RISC-V with -O3, the C++ program

int f() {}

emits a completely empty function.

It correctly warns about the missing return statement, but also does not emit a
"ret" instruction.

[Bug target/113981] risc-v: non-void C++ function with no return statement has no ret

[pinskia at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=113981

Andrew Pinski <pinskia at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |RESOLVED
         Resolution|---                         |DUPLICATE

--- Comment #1 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
>but also does not emit a "ret" instruction.

Because it is undefined in C++ to return from a fuction without a value.

*** This bug has been marked as a duplicate of bug 86761 ***

[Bug target/113981] risc-v: non-void C++ function with no return statement has no ret

[redi at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=113981

--- Comment #2 from Jonathan Wakely <redi at gcc dot gnu.org> ---
With -O0 or -fsanitize-trap=return you get a trap. With -fsanitize=return you
get a UBsan error. With -O3 you asked the compiler to optimize the heck out of
a function with undefined behaviour, what do you expect?

Either that function is never called (in which case why would you want a wasted
ret instruction increasing the binary size?) or it's called and has undefined
behaviour, which is not going to end well with -O3.

Why would you not just fix it when you see the warning?