[Bug c++/54278] New: "control reaches end of non-void function

[Bug c++/54278] New: "control reaches end of non-void function

[travis at gockelhut dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=54278

             Bug #: 54278
           Summary: "control reaches end of non-void function
    Classification: Unclassified
           Product: gcc
           Version: unknown
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
        AssignedTo: unassigned@gcc.gnu.org
        ReportedBy: travis@gockelhut.com


Created attachment 28027
  --> http://gcc.gnu.org/bugzilla/attachment.cgi?id=28027
compile with g++-4.7 -Wreturn-type to recreate

struct ThingWithDtor
    {
        ~ThingWithDtor();
    };

    struct Aborter
    {
        __attribute__((noreturn)) ~Aborter();
    };

    int foo(int x)
    {
        ThingWithDtor t __attribute__((unused));
        if (x)
            return x;
        Aborter();
    }


noreturn.cpp: In function ‘int foo(int)’:
noreturn.cpp:16:1: warning: control reaches end of non-void function
[-Wreturn-type]

[Bug c++/54278] __attribute__((noreturn)) called from destructor when another auto-scoped variable has a non-trivial dtor erroneously fails with "control reaches end of non-void function" at -O0

[travis at gockelhut dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=54278

Travis Gockel <travis at gockelhut dot com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
            Version|unknown                     |4.7.0
            Summary|"control reaches end of     |__attribute__((noreturn))
                   |non-void function           |called from destructor when
                   |                            |another auto-scoped
                   |                            |variable has a non-trivial
                   |                            |dtor erroneously fails with
                   |                            |"control reaches end of
                   |                            |non-void function" at -O0

--- Comment #1 from Travis Gockel <travis at gockelhut dot com> 2012-08-16 00:06:48 UTC ---
Accidentally hit enter...

The key here is that ThingWithDtor is non-trivial -- if you mark
~ThingWithDtor() as =default (or remove the declaration), it will not warn. If
you call a noreturn function directly instead of relying on ~Aborter(), it will
not warn. If both branches of the if create an Aborter, it will not warn.


Everything must be compiled with -Wreturn-type and -O0. This all compiles just
fine with g++ 4.6.3.

---

Using built-in specs.
COLLECT_GCC=g++-4.7
COLLECT_LTO_WRAPPER=/usr/lib/gcc/x86_64-linux-gnu/4.7/lto-wrapper
Target: x86_64-linux-gnu
Configured with: ../src/configure -v --with-pkgversion='Ubuntu/Linaro
4.7.0-7ubuntu3' --with-bugurl=file:///usr/share/doc/gcc-4.7/README.Bugs
--enable-languages=c,c++,go,fortran,objc,obj-c++ --prefix=/usr
--program-suffix=-4.7 --enable-shared --enable-linker-build-id
--with-system-zlib --libexecdir=/usr/lib --without-included-gettext
--enable-threads=posix --with-gxx-include-dir=/usr/include/c++/4.7
--libdir=/usr/lib --enable-nls --disable-bootstrap --with-sysroot=/
--enable-clocale=gnu --enable-libstdcxx-debug --enable-libstdcxx-time=yes
--enable-gnu-unique-object --enable-plugin --enable-objc-gc --disable-werror
--with-arch-32=i686 --with-tune=generic --enable-checking=release
--build=x86_64-linux-gnu --host=x86_64-linux-gnu --target=x86_64-linux-gnu
Thread model: posix
gcc version 4.7.0 (Ubuntu/Linaro 4.7.0-7ubuntu3)

[Bug c++/54278] __attribute__((noreturn)) called from destructor when another auto-scoped variable has a non-trivial dtor erroneously fails with "control reaches end of non-void function" at -O0

[paolo.carlini at oracle dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=54278

Paolo Carlini <paolo.carlini at oracle dot com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |NEW
   Last reconfirmed|                            |2013-08-21
                 CC|travis at gockelhut dot com        |
     Ever confirmed|0                           |1

[Bug c++/54278] [6 regression] __attribute__((noreturn)) called from destructor when another auto-scoped variable has a non-trivial dtor erroneously fails with "control reaches end of non-void function" at -O0

[danikiw542 at bcpfm dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=54278

danikiw542 at bcpfm dot com changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |danikiw542 at bcpfm dot com

--- Comment #8 from danikiw542 at bcpfm dot com ---
This warning is as the admonition portrayed In kind with no value. If control
arrives at the end of a function and no return is encountered, GCC accepts an
arrival with no arrival value. However, for this, the capacity requires an
arrival value. Toward the finish of the function, return suitable value,
regardless of whether control never comes there.

Also you can solve that by doing follows:
The problem is that other compilers have a warning about "unreachable code". If
every switch case is handled, the compiler detects that the return statement
cannot be reached. I have to suppress this warning or use the preprocessor to
only have that return statement on certain compilers. Something like this piece
of code.   Link to the code.

https://kodlogs.com/blog/852/warning-control-reaches-end-non-void-function-wreturn-type

[Bug c++/54278] [6 regression] __attribute__((noreturn)) called from destructor when another auto-scoped variable has a non-trivial dtor erroneously fails with "control reaches end of non-void function" at -O0

[pinskia at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=54278

--- Comment #9 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
(In reply to danikiw542 from comment #8)
> https://kodlogs.com/blog/852/warning-control-reaches-end-non-void-function-
> wreturn-type


values not defined in enum's are still valid and well defined, that is a
different issue all together and unrelated to this bug.  There are others which
have been closed as invalid for the reason mentioned here.