[Bug c/12603] New: No return statement warning on function that never returns with -O3

[Bug c/12603] New: No return statement warning on function that never returns with -O3

[james at ittc dot ku dot edu]

PLEASE REPLY TO gcc-bugzilla@gcc.gnu.org ONLY, *NOT* gcc-bugs@gcc.gnu.org.

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=12603

           Summary: No return statement warning on function that never
                    returns with -O3
           Product: gcc
           Version: 3.3.1
            Status: UNCONFIRMED
          Severity: minor
          Priority: P3
         Component: c
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: james at ittc dot ku dot edu
                CC: gcc-bugs at gcc dot gnu dot org,james at ittc dot ku dot
                    edu
 GCC build triplet: i686-pc-linux-gnu
  GCC host triplet: i686-pc-linux-gnu
GCC target triplet: i686-pc-linux-gnu

The following function compiles without warning at optimization level -O2 or
below.  With -Wall -O3, gcc says:

noreturn.c: In function `this_function_never_returns':
noreturn.c:5: warning: no return statement in function returning non-void

This happens with gcc 3.2.2 - 3.3.1, at least.

int
this_function_never_returns ()
{
  for (;;);
}

This is an extremely stripped down version of a problem with XEmacs and
Fcommand_loop_1, which must be declared to return a Lisp_Object (since it is a
Lisp-visible function), but which contains an infinite loop.  The obvious
solution of putting a return statement at the end causes some compilers to
complain about unreachable code.  Adding __attribute__ ((noreturn)) did not make
the warning go away.

[Bug optimization/12603] No return statement warning on function that never returns with -O3

[pinskia at gcc dot gnu dot org]

PLEASE REPLY TO gcc-bugzilla@gcc.gnu.org ONLY, *NOT* gcc-bugs@gcc.gnu.org.

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=12603


pinskia at gcc dot gnu dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |NEW
          Component|c                           |optimization
     Ever Confirmed|                            |1
           Keywords|                            |diagnostic
   Last reconfirmed|0000-00-00 00:00:00         |2003-10-18 17:44:11
               date|                            |


------- Additional Comments From pinskia at gcc dot gnu dot org  2003-10-18 17:44 -------
This should not warn at -O3, I think this is related to the control flow graph some how.

[Bug optimization/12603] No return statement warning on function that never returns with -O3

[kazu at cs dot umass dot edu]

------- Additional Comments From kazu at cs dot umass dot edu  2003-11-24 20:54 -------
This problem does not seem to occur with gcc-3.4 20031124.


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=12603

[Bug optimization/12603] No return statement warning on function that never returns with -O3

[pinskia at gcc dot gnu dot org]

------- Additional Comments From pinskia at gcc dot gnu dot org  2003-11-24 22:51 -------
I can still reproduce it with the mainline (20031124).

-- 
           What    |Removed                     |Added
----------------------------------------------------------------------------
   Last reconfirmed|2003-10-18 17:44:11         |2003-11-24 22:51:09
               date|                            |


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=12603

[Bug c/12603] No return statement warning on function that never returns with -O3

[pinskia at gcc dot gnu dot org]

------- Additional Comments From pinskia at gcc dot gnu dot org  2004-03-06 05:48 -------
The problem is that -O3, DECL_INLINE for the function decl becomes true because -O3 
enables -finline-functions.  So it looks like a different check is needed for the C front-end.

-- 
           What    |Removed                     |Added
----------------------------------------------------------------------------
          Component|optimization                |c


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=12603

[Bug c/12603] No return statement warning on function that never returns with -O3

[zwin at users dot sourceforge dot net]

------- Additional Comments From zwin at users dot sourceforge dot net  2004-05-02 15:36 -------
I am also getting this warning about no return statement for methods in C++.
While a global function int noret() { for (;;); } does not fire the warning, the
same in a method does (3.2.3).

-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=12603

[Bug c/12603] No return statement warning on function that never returns with -O3

[pinskia at gcc dot gnu dot org]

------- Comment #10 from pinskia at gcc dot gnu dot org  2008-10-20 20:42 -------
(In reply to comment #9)
> This got fixed somehow. There is a testcase in the testsuite to make sure we do
> not regress.

This was most likely fixed by:
2008-09-17  Jan Hubicka  <jh@suse.cz>

        PR c++/18071
        * tree.h (DECL_INLINE): remove.
        (DECL_DECLARED_INLINE_P): Update docs.
        (DECL_NO_INLINE_WARNING_P): new.
        (tree_function_decl): Replace inline_flag by no_inline_warning_flag.
        * tree-inline.c (inlinable_function_p): Set DECL_NO_INLINE_WARNING_P.

:)
Which removed DECL_INLINE.  As I mentioned in comment #4 DECL_INLINE was the
issue.


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=12603

[Bug c/12603] No return statement warning on function that never returns with -O3

[manu at gcc dot gnu dot org]

------- Comment #9 from manu at gcc dot gnu dot org  2008-10-20 18:28 -------
This got fixed somehow. There is a testcase in the testsuite to make sure we do
not regress.


-- 

manu at gcc dot gnu dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|ASSIGNED                    |RESOLVED
         Resolution|                            |FIXED


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=12603

[Bug c/12603] No return statement warning on function that never returns with -O3

[manu at gcc dot gnu dot org]

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------- Comment #8 from manu at gcc dot gnu dot org  2008-10-20 18:27 -------
Subject: Bug 12603

Author: manu
Date: Mon Oct 20 18:26:21 2008
New Revision: 141244

URL: http://gcc.gnu.org/viewcvs?root=gcc&view=rev&rev=141244
Log:
2008-10-20  Manuel López-Ibáñez  <manu@gcc.gnu.org>

        PR 12603
        * gcc.dg/pr12603.c: New testcase.

Added:
    trunk/gcc/testsuite/gcc.dg/pr12603.c
Modified:
    trunk/gcc/testsuite/ChangeLog


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=12603

[Bug c/12603] No return statement warning on function that never returns with -O3

[manu at gcc dot gnu dot org]

------- Comment #7 from manu at gcc dot gnu dot org  2008-08-29 13:28 -------
No warning in GCC 4.4 with any of those:

-O0 -Wall -Wextra -Wreturn-type -Wunreachable-code
-O1 -Wall -Wextra -Wreturn-type -Wunreachable-code
-O2 -Wall -Wextra -Wreturn-type -Wunreachable-code
-O3 -Wall -Wextra -Wreturn-type -Wunreachable-code
-O3 -finline -Wall -Wextra -Wreturn-type -Wunreachable-code

If you can reproduce the problem in a recent GCC, let us know. I will add the
testcase to the testsuite before closing this.


-- 

manu at gcc dot gnu dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
         AssignedTo|unassigned at gcc dot gnu   |manu at gcc dot gnu dot org
                   |dot org                     |
             Status|NEW                         |ASSIGNED
      Known to fail|                            |4.4.0
   Last reconfirmed|2005-12-18 00:38:04         |2008-08-29 13:28:06
               date|                            |


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=12603

[Bug c/12603] No return statement warning on function that never returns with -O3

[pinskia at gcc dot gnu dot org]

------- Comment #6 from pinskia at gcc dot gnu dot org  2007-02-15 19:30 -------
*** Bug 30794 has been marked as a duplicate of this bug. ***


-- 

pinskia at gcc dot gnu dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |ian at airs dot com


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=12603