[Bug optimization/13000] New: Using -Ox cannot detect missing return statement in a function

[Bug optimization/13000] New: Using -Ox cannot detect missing return statement in a function

[cheng at powertv dot com]

In the following contrived code snippet, gcc 2.953 will not complain about the 
function not returning a value despite its function signature says so when 
compiling with optimizations enabled (e.g. -O1 or -O2).  Disabling 
optimizations with -O0 will enable the compiler to display an appropriate error 
message.  This problem appears in both C and C++ test code.


typedef int ui32;

static ui32 AddPrimitiveDvrResource(ui32 hSession, ui32 *pSessNode,
									
	void *pvResourceDescriptor, ui32 dwSize);

static ui32 AddPrimitiveDvrResource(ui32 hSession, ui32 *pSessNode,
									
	void *pvResourceDescriptor, ui32 dwSize)
{
	ui32 rc;

	if (dwSize != 32)
	{
		rc = 0;
	}
	else
	{
		// set the DVR ID in the session node even if subsequent steps 
fail
		
		if (dwSize) 
		{
			rc = dwSize;
		}
		else
		{
			if (!pSessNode)
			{
				rc = 2;
			}
			else
			{
				ui32 dwTranscryptorAvrID = 0;
	
				if (rc = dwTranscryptorAvrID)
				{
					dwTranscryptorAvrID;
				}
				else
				{
					ui32 dk;

					if (rc = 16)
					{
						dk = rc;
					}
					else
					{
						if (dk) 
						{
							rc = 1;
						}
						else
						{
							rc = 0;
						}
					}
				}
			}
		}
	}
}

int main(int argc, char **argv)
{
	int result = AddPrimitiveDvrResource(0,0,0,0);

	return 0;
}

-- 
           Summary: Using -Ox cannot detect missing return statement in a
                    function
           Product: gcc
           Version: 2.95.3
            Status: UNCONFIRMED
          Severity: normal
          Priority: P2
         Component: optimization
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: cheng at powertv dot com
                CC: gcc-bugs at gcc dot gnu dot org


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=13000

[Bug optimization/13000] Using -Ox cannot detect missing return statement in a function

[pinskia at gcc dot gnu dot org]

------- Additional Comments From pinskia at gcc dot gnu dot org  2003-11-10 23:13 -------
Been fixed since at least 3.1.

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


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=13000

[Bug optimization/13000] Using -Ox cannot detect missing return statement in a function

[falk dot hueffner at student dot uni-tuebingen dot de]

------- Additional Comments From falk dot hueffner at student dot uni-tuebingen dot de  2003-11-10 23:29 -------
Subject: Re:  Using -Ox cannot detect missing return statement in a function

"pinskia at gcc dot gnu dot org" <gcc-bugzilla@gcc.gnu.org> writes:

> ------- Additional Comments From pinskia at gcc dot gnu dot org  2003-11-10 23:13 -------
> Been fixed since at least 3.1.

Seems to be back in tree-ssa though (warning at -O0, -O1 and -O3, but
not at -O2, weird).  Unfortunately, I don't have a mainline compiler
to check right now.



-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=13000

[Bug optimization/13000] [tree-ssa] Using -Ox cannot detect missing return statement in a function

[pinskia at gcc dot gnu dot org]

------- Additional Comments From pinskia at gcc dot gnu dot org  2003-11-10 23:36 -------
Reopening based on Falk's tree-ssa problem.

-- 
           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|RESOLVED                    |UNCONFIRMED
           Keywords|                            |diagnostic
         Resolution|FIXED                       |
            Summary|Using -Ox cannot detect     |[tree-ssa] Using -Ox cannot
                   |missing return statement in |detect missing return
                   |a function                  |statement in a function
   Target Milestone|---                         |tree-ssa


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=13000

[Bug optimization/13000] [tree-ssa] Using -Ox cannot detect missing return statement in a function

[pinskia at gcc dot gnu dot org]

-- 
           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |NEW
     Ever Confirmed|                            |1
   Last reconfirmed|0000-00-00 00:00:00         |2003-11-11 00:20:32
               date|                            |


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=13000

[Bug optimization/13000] [tree-ssa] Using -Ox cannot detect missing return statement in a function

[steven at gcc dot gnu dot org]

-- 
           What    |Removed                     |Added
----------------------------------------------------------------------------
OtherBugsDependingO|                            |13127
              nThis|                            |


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=13000

[Bug optimization/13000] [3.4 Regression] Using -Ox cannot detect missing return statement in a function

[pinskia at gcc dot gnu dot org]

------- Additional Comments From pinskia at gcc dot gnu dot org  2003-12-01 04:34 -------
I can also reproduce this on the mainline (20031119).

-- 
           What    |Removed                     |Added
----------------------------------------------------------------------------
   Last reconfirmed|2003-11-11 00:20:32         |2003-12-01 04:34:28
               date|                            |
            Summary|[tree-ssa] Using -Ox cannot |[3.4 Regression] Using -Ox
                   |detect missing return       |cannot detect missing return
                   |statement in a function     |statement in a function
   Target Milestone|tree-ssa                    |3.4
            Version|tree-ssa                    |3.4


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=13000

[Bug optimization/13000] [3.4 Regression] Using -O2 cannot detect missing return statement in a function

[pinskia at gcc dot gnu dot org]

------- Additional Comments From pinskia at gcc dot gnu dot org  2003-12-25 00:10 -------
>From Phil's regression hunter:
: Search converges between 2003-09-04-trunk (#391) and 2003-09-05-trunk (#392).
Before that GCC gave at -O2:
input.c: In function `AddPrimitiveDvrResource':
input.c:41: warning: statement with no effect
input.c:10: warning: unused parameter 'hSession'
input.c:12: warning: unused parameter 'pvResourceDescriptor'


-- 
           What    |Removed                     |Added
----------------------------------------------------------------------------
   Last reconfirmed|2003-12-01 04:34:28         |2003-12-25 00:10:12
               date|                            |
            Summary|[3.4 Regression] Using -Ox  |[3.4 Regression] Using -O2
                   |cannot detect missing return|cannot detect missing return
                   |statement in a function     |statement in a function


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=13000

[Bug optimization/13000] [3.4 Regression] [unit-at-a-time] Using -O2 cannot detect missing return statement in a function

[pinskia at gcc dot gnu dot org]

------- Additional Comments From pinskia at gcc dot gnu dot org  2003-12-25 00:22 -------
It also works with -fno-unit-at-a-time or with -O3.
Jan could look into what causes this?

-- 
           What    |Removed                     |Added
----------------------------------------------------------------------------
         AssignedTo|unassigned at gcc dot gnu   |hubicka at gcc dot gnu dot
                   |dot org                     |org
             Status|NEW                         |ASSIGNED
            Summary|[3.4 Regression] Using -O2  |[3.4 Regression] [unit-at-a-
                   |cannot detect missing return|time] Using -O2 cannot
                   |statement in a function     |detect missing return
                   |                            |statement in a function


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=13000

[Bug optimization/13000] [3.4 Regression] [unit-at-a-time] Using -O2 cannot detect missing return statement in a function

[hubicka at ucw dot cz]

------- Additional Comments From hubicka at ucw dot cz  2003-12-25 16:05 -------
Subject: Re:  [3.4 Regression] [unit-at-a-time] Using -O2 cannot detect missing return statement in a function

> 
> ------- Additional Comments From pinskia at gcc dot gnu dot org  2003-12-25 00:22 -------
> It also works with -fno-unit-at-a-time or with -O3.
> Jan could look into what causes this?

This is caused by a fact that we either fully inline or decide to not
compile function at all.  Because the warning come from the brackend, we
never notice it.  This is kind of problem we had all the time, just it
is more common now.  I hope to do something about it in a tree-ssa
branch.

Honza
> 
> -- 
>            What    |Removed                     |Added
> ----------------------------------------------------------------------------
>          AssignedTo|unassigned at gcc dot gnu   |hubicka at gcc dot gnu dot
>                    |dot org                     |org
>              Status|NEW                         |ASSIGNED
>             Summary|[3.4 Regression] Using -O2  |[3.4 Regression] [unit-at-a-
>                    |cannot detect missing return|time] Using -O2 cannot
>                    |statement in a function     |detect missing return
>                    |                            |statement in a function
> 
> 
> http://gcc.gnu.org/bugzilla/show_bug.cgi?id=13000
> 
> ------- You are receiving this mail because: -------
> You are the assignee for the bug, or are watching the assignee.


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=13000

[Bug optimization/13000] [3.4 Regression] [unit-at-a-time] Using -O2 cannot detect missing return statement in a function

[pinskia at gcc dot gnu dot org]

-- 
           What    |Removed                     |Added
----------------------------------------------------------------------------
           Severity|normal                      |minor


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=13000

[Bug optimization/13000] [3.4 Regression] [unit-at-a-time] Using -O2 cannot detect missing return statement in a function

[hubicka at gcc dot gnu dot org]

------- Additional Comments From hubicka at gcc dot gnu dot org  2004-01-03 21:21 -------
Needs the analysis done before inlining

-- 
           What    |Removed                     |Added
----------------------------------------------------------------------------
   Target Milestone|3.4.0                       |tree-ssa


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=13000

[Bug optimization/13000] [3.4/3.5 Regression] [unit-at-a-time] Using -O2 cannot detect missing return statement in a function

[pinskia at gcc dot gnu dot org]

-- 
           What    |Removed                     |Added
----------------------------------------------------------------------------
   Target Milestone|tree-ssa                    |3.5.0


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=13000

[Bug tree-optimization/13000] [3.4/3.5 Regression] [unit-at-a-time] Using -O2 cannot detect missing return statement in a function

[rth at gcc dot gnu dot org]

------- Additional Comments From rth at gcc dot gnu dot org  2004-08-18 07:35 -------
Looking at it.

-- 
           What    |Removed                     |Added
----------------------------------------------------------------------------
         AssignedTo|hubicka at gcc dot gnu dot  |rth at gcc dot gnu dot org
                   |org                         |


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=13000

[Bug tree-optimization/13000] [3.4/4.0 Regression] [unit-at-a-time] Using -O2 cannot detect missing return statement in a function

[pinskia at gcc dot gnu dot org]

------- Additional Comments From pinskia at gcc dot gnu dot org  2004-11-21 14:10 -------
*** Bug 18588 has been marked as a duplicate of this bug. ***

-- 
           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |debian-gcc at lists dot
                   |                            |debian dot org


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=13000

[Bug tree-optimization/13000] [3.4/4.0 Regression] [unit-at-a-time] Using -O2 cannot detect missing return statement in a function

[pinskia at gcc dot gnu dot org]

------- Additional Comments From pinskia at gcc dot gnu dot org  2005-01-18 00:39 -------
Hmm, This seems like a place where the tree-profiling branch can come in handing as we always 
produce the CFG for all functions even the ones which we inline and don't emit.

-- 
           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |pinskia at gcc dot gnu dot
                   |                            |org


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=13000

[Bug tree-optimization/13000] [3.4/4.0 Regression] [unit-at-a-time] Using -O2 cannot detect missing return statement in a function

[ian at airs dot com]

------- Additional Comments From ian at airs dot com  2005-01-19 15:51 -------
Proposed patch: http://gcc.gnu.org/ml/gcc-patches/2005-01/msg01223.html

-- 
           What    |Removed                     |Added
----------------------------------------------------------------------------
           Keywords|                            |patch


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=13000

[Bug tree-optimization/13000] [3.4/4.0 Regression] [unit-at-a-time] Using -O2 cannot detect missing return statement in a function

[ian at airs dot com]

------- Additional Comments From ian at airs dot com  2005-01-21 02:52 -------
Updated patch: http://gcc.gnu.org/ml/gcc-patches/2005-01/msg01443.html

-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=13000

[Bug tree-optimization/13000] [3.4/4.0 Regression] [unit-at-a-time] Using -O2 cannot detect missing return statement in a function

[cvs-commit at gcc dot gnu dot org]

------- Additional Comments From cvs-commit at gcc dot gnu dot org  2005-01-21 19:06 -------
Subject: Bug 13000

CVSROOT:	/cvs/gcc
Module name:	gcc
Changes by:	ian@gcc.gnu.org	2005-01-21 19:05:54

Modified files:
	gcc/testsuite  : ChangeLog 
	gcc/testsuite/gcc.dg: 20040206-1.c 

Log message:
	PR tree-optimization/13000
	* gcc.dg/20040206-1.c: Change warning to point where function is
	being inlined.

Patches:
http://gcc.gnu.org/cgi-bin/cvsweb.cgi/gcc/gcc/testsuite/ChangeLog.diff?cvsroot=gcc&r1=1.4917&r2=1.4918
http://gcc.gnu.org/cgi-bin/cvsweb.cgi/gcc/gcc/testsuite/gcc.dg/20040206-1.c.diff?cvsroot=gcc&r1=1.4&r2=1.5



-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=13000

[Bug tree-optimization/13000] [3.4/4.0 Regression] [unit-at-a-time] Using -O2 cannot detect missing return statement in a function

[cvs-commit at gcc dot gnu dot org]

------- Additional Comments From cvs-commit at gcc dot gnu dot org  2005-01-21 19:05 -------
Subject: Bug 13000

CVSROOT:	/cvs/gcc
Module name:	gcc
Changes by:	ian@gcc.gnu.org	2005-01-21 19:05:25

Modified files:
	gcc            : ChangeLog tree-inline.c tree-cfg.c gimple-low.c 
	                 gimplify.c c-typeck.c 

Log message:
	PR tree-optimization/13000
	* tree-inline.c: Include "tree-flow.h".
	(expand_call_inline): If warn_return_type, warn if non-void inline
	function falls through.
	* tree-cfg.c (execute_warn_function_return): Don't warn about
	control reaching end if TREE_NO_WARNING is set.  Set
	TREE_NO_WARNING.
	* gimple-low.c (block_may_fallthru): Don't assume that SWITCH_EXPR
	has been lowered.
	* gimplify.c (shortcut_cond_expr): Don't emit a jump over the else
	branch if we don't need one.
	* c-typeck.c: Include "tree-flow.h"
	(c_finish_bc_stmt): Don't add a goto if the current statement
	list doesn't fall through to the current point.

Patches:
http://gcc.gnu.org/cgi-bin/cvsweb.cgi/gcc/gcc/ChangeLog.diff?cvsroot=gcc&r1=2.7221&r2=2.7222
http://gcc.gnu.org/cgi-bin/cvsweb.cgi/gcc/gcc/tree-inline.c.diff?cvsroot=gcc&r1=1.166&r2=1.167
http://gcc.gnu.org/cgi-bin/cvsweb.cgi/gcc/gcc/tree-cfg.c.diff?cvsroot=gcc&r1=2.144&r2=2.145
http://gcc.gnu.org/cgi-bin/cvsweb.cgi/gcc/gcc/gimple-low.c.diff?cvsroot=gcc&r1=2.17&r2=2.18
http://gcc.gnu.org/cgi-bin/cvsweb.cgi/gcc/gcc/gimplify.c.diff?cvsroot=gcc&r1=2.104&r2=2.105
http://gcc.gnu.org/cgi-bin/cvsweb.cgi/gcc/gcc/c-typeck.c.diff?cvsroot=gcc&r1=1.411&r2=1.412



-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=13000

[Bug tree-optimization/13000] [3.4 Regression] [unit-at-a-time] Using -O2 cannot detect missing return statement in a function

[ian at airs dot com]

------- Additional Comments From ian at airs dot com  2005-01-21 19:07 -------
Fixed on mainline.

-- 
           What    |Removed                     |Added
----------------------------------------------------------------------------
      Known to fail|4.0.0 3.4.0                 |3.4.0
      Known to work|3.3                         |3.3 4.0.0
            Summary|[3.4/4.0 Regression] [unit- |[3.4 Regression] [unit-at-a-
                   |at-a-time] Using -O2 cannot |time] Using -O2 cannot
                   |detect missing return       |detect missing return
                   |statement in a function     |statement in a function
   Target Milestone|4.0.0                       |3.4.4


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=13000

[Bug tree-optimization/13000] [3.4 Regression] [unit-at-a-time] Using -O2 cannot detect missing return statement in a function

[ian at airs dot com]

------- Additional Comments From ian at airs dot com  2005-01-21 19:14 -------
Note that if we do move to a better solution, i.e., building a CFG for inline
functions, we should remove the patch to c_finish_bc_stmt in c-typeck.c.  It
prevents -Wunreachable from ever warning about an unreachable break or continue
statement (we currently do not issue a warning about those statements anyhow).

We may want to consider removing the patch to shortcut_cond_expr in gimplify.c,
although that one is relatively harmless.

And of course if we build a CFG, we should adjust the patch to
expand_call_inline, although that will probably be pretty obvious.

See the e-mail thread starting here:
    http://gcc.gnu.org/ml/gcc-patches/2005-01/msg01223.html

-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=13000

[Bug tree-optimization/13000] [3.4 Regression] [unit-at-a-time] Using -O2 cannot detect missing return statement in a function

[rth at gcc dot gnu dot org]

------- Additional Comments From rth at gcc dot gnu dot org  2005-01-27 01:58 -------
I am uninterested in fixing this for 3.4.

-- 
           What    |Removed                     |Added
----------------------------------------------------------------------------
         AssignedTo|rth at gcc dot gnu dot org  |unassigned at gcc dot gnu
                   |                            |dot org
             Status|ASSIGNED                    |NEW


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=13000

[Bug tree-optimization/13000] [3.4 Regression] [unit-at-a-time] Using -O2 cannot detect missing return statement in a function

[giovannibajo at libero dot it]

------- Additional Comments From giovannibajo at libero dot it  2005-04-12 17:35 -------
Since this bug was fixed in 4.1, I'm removing the dependencies with the 4.1 
metabug.

-- 
           What    |Removed                     |Added
----------------------------------------------------------------------------
OtherBugsDependingO|17652                       |
              nThis|                            |


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=13000

[Bug tree-optimization/13000] [3.4 Regression] [unit-at-a-time] Using -O2 cannot detect missing return statement in a function

[ian at airs dot com]

------- Additional Comments From ian at airs dot com  2005-04-12 18:49 -------
The dependency on 17652 is there because of comment #17, q.v.  We want to make
sure that we back out the patch to c_finish_bc_stmt when it is no longer needed,
which should happen after the tree-profiling branch is merged to mainline.  So
I'm re-adding the dependency.  If you still think this is wrong, go ahead and
take it out.

-- 
           What    |Removed                     |Added
----------------------------------------------------------------------------
OtherBugsDependingO|                            |17652
              nThis|                            |


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=13000

[Bug tree-optimization/13000] [3.4 Regression] [unit-at-a-time] Using -O2 cannot detect missing return statement in a function

[mmitchel at gcc dot gnu dot org]

-- 
           What    |Removed                     |Added
----------------------------------------------------------------------------
   Target Milestone|3.4.4                       |3.4.5


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=13000

[Bug tree-optimization/13000] [3.4 Regression] [unit-at-a-time] Using -O2 cannot detect missing return statement in a function

[pinskia at gcc dot gnu dot org]

------- Additional Comments From pinskia at gcc dot gnu dot org  2005-09-05 15:48 -------
(In reply to comment #20)
> The dependency on 17652 is there because of comment #17, q.v.  We want to make
> sure that we back out the patch to c_finish_bc_stmt when it is no longer needed,
> which should happen after the tree-profiling branch is merged to mainline.  So
> I'm re-adding the dependency.  If you still think this is wrong, go ahead and
> take it out.

Removing dependent on 13127 because the patch to c_finish_bc_stmt still speeds up the compiling as 
we don't need to generate as many BBs with it as we would without it.

-- 
           What    |Removed                     |Added
----------------------------------------------------------------------------
OtherBugsDependingO|17652                       |
              nThis|                            |


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=13000