[Bug c++/48087] New: -Wall -Werror adds warnings over and above those generated by -Wall

[Bug c++/48087] New: -Wall -Werror adds warnings over and above those generated by -Wall

[cgd at google dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=48087

           Summary: -Wall -Werror adds warnings over and above those
                    generated by -Wall
           Product: gcc
           Version: 4.6.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
        AssignedTo: unassigned@gcc.gnu.org
        ReportedBy: cgd@google.com


was checking the status of the code in PR33752 against 4.6, and discovered that
under GCC pre-4.6,

    -Wall -Werror

causes more errors/warnings to be generated than just -Wall.

See code an examples below.

This is a bit surprising; certainly, the manual just says:

       -Werror
           Make all warnings into errors.

the 4.4.x (and earlier) behaviour of stopping earlier (exiting after the first
error, in this example) is not ideal, but IMO is less surprising than having
-Werror *add* errors.


the test input file from PR33752, placed into x.cc:

class Alpha {
 public:
   Alpha() { }
   ~Alpha();
};

class Beta {
 public:
   Beta() { }
   ~Beta() __attribute__((noreturn));
   bool value() { return false; }
};

bool Gamma(bool b) {
 return b;
}

bool DeltaOne(bool b) {
 Alpha s;
 bool b2 = Beta().value();
 Gamma(b2);
}

bool DeltaTwo(bool b) {
 if (b) {
   return false;
 } else {
   bool b2 = Beta().value();
   Gamma(Beta().value());
 }
}

bool DeltaThree(bool b) {
 Alpha s;

 if (b) {
   return false;
 } else {
   bool b2 = Beta().value();
   Gamma(b2);
 }
}


GCC 4.4.5 (from ftp.gnu.org):

$ inst/bin/gcc --version | head -1
gcc (GCC) 4.4.5
$ 

$ inst/bin/gcc -c /tmp/x.cc -Wall
/tmp/x.cc: In function 'bool DeltaTwo(bool)':
/tmp/x.cc:28: warning: unused variable 'b2'
/tmp/x.cc: In function 'bool DeltaThree(bool)':
/tmp/x.cc:42: warning: control reaches end of non-void function
$ 

-> 2 warnings.

$ inst/bin/gcc -c /tmp/x.cc -Wall -Werror
cc1plus: warnings being treated as errors
/tmp/x.cc: In function 'bool DeltaTwo(bool)':
/tmp/x.cc:28: error: unused variable 'b2'
$ 

-> 1 error, stopping after the first.  not necessarily perfect, but OK.


GCC 4.5.2 (from ftp.gnu.org):

$ inst/bin/gcc --version | head -1
gcc (GCC) 4.5.2
$ 

$ inst/bin/gcc -c /tmp/x.cc -Wall
/tmp/x.cc: In function 'bool DeltaTwo(bool)':
/tmp/x.cc:28:9: warning: unused variable 'b2'
/tmp/x.cc: In function 'bool DeltaThree(bool)':
/tmp/x.cc:42:1: warning: control reaches end of non-void function
$ 

-> 2 warnings

$ inst/bin/gcc -c /tmp/x.cc -Wall -Werror
cc1plus: warnings being treated as errors
/tmp/x.cc: In function 'bool DeltaTwo(bool)':
/tmp/x.cc:28:9: error: unused variable 'b2'
/tmp/x.cc: In function 'bool DeltaThree(bool)':
/tmp/x.cc:42:1: error: control reaches end of non-void function
/tmp/x.cc: In function 'bool DeltaTwo(bool)':
/tmp/x.cc:31:1: error: control reaches end of non-void function
/tmp/x.cc: In function 'bool DeltaOne(bool)':
/tmp/x.cc:22:1: error: control reaches end of non-void function
$ 

-> 4 errors.  Huh?


GCC pre-4.6 (svn trunk as of yesterday):

$ inst/bin/gcc --version | head -1
gcc (GCC) 4.6.0 20110311 (experimental)
$ 

$ inst/bin/gcc -c /tmp/x.cc -Wall
/tmp/x.cc: In function 'bool DeltaTwo(bool)':
/tmp/x.cc:28:9: warning: unused variable 'b2' [-Wunused-variable]
/tmp/x.cc: In function 'bool DeltaThree(bool)':
/tmp/x.cc:42:1: warning: control reaches end of non-void function
[-Wreturn-type]
$ 

-> 2 warnings.

$ inst/bin/gcc -c /tmp/x.cc -Wall -Werror
/tmp/x.cc: In function 'bool DeltaTwo(bool)':
/tmp/x.cc:28:9: error: unused variable 'b2' [-Werror=unused-variable]
/tmp/x.cc: In function 'bool DeltaThree(bool)':
/tmp/x.cc:42:1: error: control reaches end of non-void function
[-Werror=return-type]
/tmp/x.cc: In function 'bool DeltaTwo(bool)':
/tmp/x.cc:31:1: error: control reaches end of non-void function
[-Werror=return-type]
/tmp/x.cc: In function 'bool DeltaOne(bool)':
/tmp/x.cc:22:1: error: control reaches end of non-void function
[-Werror=return-type]
cc1plus: all warnings being treated as errors

$ 

-> 4 errors.  Same as 4.6, but still "huh?"

[Bug c++/48087] -Wall -Werror adds warnings over and above those generated by -Wall

[paolo.carlini at oracle dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=48087

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |jakub at gcc dot gnu.org,
                   |                            |rguenth at gcc dot gnu.org

--- Comment #1 from Paolo Carlini <paolo.carlini at oracle dot com> 2011-10-18 00:53:48 UTC ---
Chris, did you ever see something similar for other warnings besides 'control
reaches end of non-void function'?

Because the latter is "special" in that isn't produced by the C++ front-end by
itself, and is also known to be affected by at least another annoying issue,
see PR49508. Humm, are we talking about the same issue actually?

In case, would it be hard to implement what Jakub suggested in PR49508?

[Bug c++/48087] -Wall -Werror adds warnings over and above those generated by -Wall

[paolo.carlini at oracle dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=48087

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |NEW
   Last reconfirmed|                            |2011-10-18
                 CC|                            |paolo.carlini at oracle dot
                   |                            |com
     Ever Confirmed|0                           |1

--- Comment #2 from Paolo Carlini <paolo.carlini at oracle dot com> 2011-10-18 01:18:24 UTC ---
Well, this does, it (fixes both) but I don't know if we are aiming for
something better, no good including the whole "diagnostic.h"?!?

Index: tree-cfg.c
===================================================================
--- tree-cfg.c    (revision 180119)
+++ tree-cfg.c    (working copy)
@@ -37,7 +37,7 @@ along with GCC; see the file COPYING3.  If not see
 #include "timevar.h"
 #include "tree-dump.h"
 #include "tree-pass.h"
-#include "diagnostic-core.h"
+#include "diagnostic.h"
 #include "except.h"
 #include "cfgloop.h"
 #include "cfglayout.h"
@@ -7380,7 +7380,8 @@ execute_warn_function_return (void)
   else if (warn_return_type
        && !TREE_NO_WARNING (cfun->decl)
        && EDGE_COUNT (EXIT_BLOCK_PTR->preds) > 0
-       && !VOID_TYPE_P (TREE_TYPE (TREE_TYPE (cfun->decl))))
+       && !VOID_TYPE_P (TREE_TYPE (TREE_TYPE (cfun->decl)))
+       && !errorcount)
     {
       FOR_EACH_EDGE (e, ei, EXIT_BLOCK_PTR->preds)
     {

[Bug c++/48087] -Wall -Werror adds warnings over and above those generated by -Wall

[paolo.carlini at oracle dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=48087

--- Comment #3 from Paolo Carlini <paolo.carlini at oracle dot com> 2011-10-18 01:22:07 UTC ---
*** Bug 49508 has been marked as a duplicate of this bug. ***

[Bug middle-end/48087] [4.5/4.6/4.7 Regression] -Wall -Werror adds warnings over and above those generated by -Wall

[paolo.carlini at oracle dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=48087

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
           Keywords|                            |diagnostic
          Component|c++                         |middle-end
            Summary|-Wall -Werror adds warnings |[4.5/4.6/4.7 Regression]
                   |over and above those        |-Wall -Werror adds warnings
                   |generated by -Wall          |over and above those
                   |                            |generated by -Wall

--- Comment #4 from Paolo Carlini <paolo.carlini at oracle dot com> 2011-10-18 01:30:26 UTC ---
This should be middle-end, and strictly speaking a regression.

[Bug middle-end/48087] [4.5/4.6/4.7 Regression] -Wall -Werror adds warnings over and above those generated by -Wall

[rguenther at suse dot de]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=48087

--- Comment #5 from rguenther at suse dot de <rguenther at suse dot de> 2011-10-18 08:26:04 UTC ---
On Tue, 18 Oct 2011, paolo.carlini at oracle dot com wrote:

> http://gcc.gnu.org/bugzilla/show_bug.cgi?id=48087
> 
> Paolo Carlini <paolo.carlini at oracle dot com> changed:
> 
>            What    |Removed                     |Added
> ----------------------------------------------------------------------------
>              Status|UNCONFIRMED                 |NEW
>    Last reconfirmed|                            |2011-10-18
>                  CC|                            |paolo.carlini at oracle dot
>                    |                            |com
>      Ever Confirmed|0                           |1
> 
> --- Comment #2 from Paolo Carlini <paolo.carlini at oracle dot com> 2011-10-18 01:18:24 UTC ---
> Well, this does, it (fixes both) but I don't know if we are aiming for
> something better, no good including the whole "diagnostic.h"?!?
> 
> Index: tree-cfg.c
> ===================================================================
> --- tree-cfg.c    (revision 180119)
> +++ tree-cfg.c    (working copy)
> @@ -37,7 +37,7 @@ along with GCC; see the file COPYING3.  If not see
>  #include "timevar.h"
>  #include "tree-dump.h"
>  #include "tree-pass.h"
> -#include "diagnostic-core.h"
> +#include "diagnostic.h"
>  #include "except.h"
>  #include "cfgloop.h"
>  #include "cfglayout.h"
> @@ -7380,7 +7380,8 @@ execute_warn_function_return (void)
>    else if (warn_return_type
>         && !TREE_NO_WARNING (cfun->decl)
>         && EDGE_COUNT (EXIT_BLOCK_PTR->preds) > 0
> -       && !VOID_TYPE_P (TREE_TYPE (TREE_TYPE (cfun->decl))))
> +       && !VOID_TYPE_P (TREE_TYPE (TREE_TYPE (cfun->decl)))
> +       && !errorcount)
>      {
>        FOR_EACH_EDGE (e, ei, EXIT_BLOCK_PTR->preds)
>      {

I don't think that's good.  You'll miss the warning for subsequent
functions that do not have errors for example.

Either we want to generally supress all warnings once we emitted
an error (then this should be done in generic diagnostic machinery),
or we shouldn't bother with this.  We can make the generic machinery
track errors per function if we like to.

[Bug middle-end/48087] [4.5/4.6/4.7 Regression] -Wall -Werror adds warnings over and above those generated by -Wall

[paolo.carlini at oracle dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=48087

--- Comment #6 from Paolo Carlini <paolo.carlini at oracle dot com> 2011-10-18 09:41:11 UTC ---
Indeed, after a day of work I should not even try sending drafts. Anyway, the
substantive point I was missing is *per function*.

Is there a simple explanation for why the problem didn't show up in 4.4.x?

[Bug middle-end/48087] [4.5/4.6/4.7 Regression] -Wall -Werror adds warnings over and above those generated by -Wall

[manu at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=48087

Manuel López-Ibáñez <manu at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |manu at gcc dot gnu.org

--- Comment #7 from Manuel López-Ibáñez <manu at gcc dot gnu.org> 2011-10-18 15:42:42 UTC ---
> Is there a simple explanation for why the problem didn't show up in 4.4.x?

The question is why control does not reach the warning() when -Werror is not
given. Are the warnings appropriate or bogus?

If the warnings are bogus (because they refer to the same function), then I
guess that the code path for warnings_as_error does not set TREE_NO_WARNING()
at some point.

[Bug middle-end/48087] [4.5/4.6/4.7 Regression] -Wall -Werror adds warnings over and above those generated by -Wall

[paolo.carlini at oracle dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=48087

--- Comment #8 from Paolo Carlini <paolo.carlini at oracle dot com> 2011-10-18 16:02:26 UTC ---
Thanks Manuel: if I understand correctly, this way we could not only avoid the
regression but even do better than 4.4, and again, the fix could be very simple
(is only hiding itself very well ;) I'll see what I can do.

[Bug middle-end/48087] [4.5/4.6/4.7 Regression] -Wall -Werror adds warnings over and above those generated by -Wall

[paolo.carlini at oracle dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=48087

--- Comment #9 from Paolo Carlini <paolo.carlini at oracle dot com> 2011-10-18 16:08:02 UTC ---
Note however that the bug I closed as duplicate of this one shows that in some
cases the problem manifests itself as *bogus* warning.. But I'm pretty sure the
issue ultimately  is one and only.

[Bug middle-end/48087] [4.5/4.6/4.7 Regression] -Wall -Werror adds warnings over and above those generated by -Wall

[manu at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=48087

--- Comment #10 from Manuel López-Ibáñez <manu at gcc dot gnu.org> 2011-10-18 20:22:52 UTC ---
The gimple generated with -Wreturn-type and with -Werror=return-type is even
different. At least at revision 164549.

*** pr48087.cc.004t.gimple-Wreturn-type 2011-10-18 22:17:16.000000000 +0200
--- pr48087.cc.004t.gimple-Werror-return-type   2011-10-18 22:17:56.000000000
+0200
***************
*** 91,127 ****
        [/home/manuel/pr48087.cc : 28:28] # USE = anything 
        # CLB = anything 
        _ZN4BetaC1EvD.2093 ([/home/manuel/pr48087.cc : 28] &D.2139);
!       [/home/manuel/pr48087.cc : 28:28] try
!         {
!           [/home/manuel/pr48087.cc : 28:28] # USE = anything 
!           # CLB = anything 
!           b2D.2138 = _ZN4Beta5valueEvD.2091 ([/home/manuel/pr48087.cc : 28]
&D.2139);
!         }
!       finally
!         {
!           [/home/manuel/pr48087.cc : 28:20] # USE = anything 
!           # CLB = anything 
!           __comp_dtor D.2097 ([/home/manuel/pr48087.cc : 28] &D.2139);
!         }
        [/home/manuel/pr48087.cc : 29:24] # USE = anything 
        # CLB = anything 
        _ZN4BetaC1EvD.2093 ([/home/manuel/pr48087.cc : 29] &D.2140);
!       [/home/manuel/pr48087.cc : 29:26] try
!         {
!           [/home/manuel/pr48087.cc : 29:24] # USE = anything 
!           # CLB = anything 
!           D.2168 = _ZN4Beta5valueEvD.2091 ([/home/manuel/pr48087.cc : 29]
&D.2140);
!           [/home/manuel/pr48087.cc : 29:25] D.2169 = (intD.2) D.2168;
!           [/home/manuel/pr48087.cc : 29:26] # USE = anything 
!           # CLB = anything 
!           _Z5GammabD.2109 (D.2169);
!         }
!       finally
!         {
!           [/home/manuel/pr48087.cc : 29:16] # USE = anything 
!           # CLB = anything 
!           __comp_dtor D.2097 ([/home/manuel/pr48087.cc : 29] &D.2140);
!         }
      }
    }
  }
--- 91,109 ----
        [/home/manuel/pr48087.cc : 28:28] # USE = anything 
        # CLB = anything 
        _ZN4BetaC1EvD.2093 ([/home/manuel/pr48087.cc : 28] &D.2139);
!       [/home/manuel/pr48087.cc : 28:28] # USE = anything 
!       # CLB = anything 
!       b2D.2138 = _ZN4Beta5valueEvD.2091 ([/home/manuel/pr48087.cc : 28]
&D.2139);
        [/home/manuel/pr48087.cc : 29:24] # USE = anything 
        # CLB = anything 
        _ZN4BetaC1EvD.2093 ([/home/manuel/pr48087.cc : 29] &D.2140);
!       [/home/manuel/pr48087.cc : 29:24] # USE = anything 
!       # CLB = anything 
!       D.2168 = _ZN4Beta5valueEvD.2091 ([/home/manuel/pr48087.cc : 29]
&D.2140);
!       [/home/manuel/pr48087.cc : 29:25] D.2169 = (intD.2) D.2168;
!       [/home/manuel/pr48087.cc : 29:26] # USE = anything 
!       # CLB = anything 
!       _Z5GammabD.2109 (D.2169);
      }
    }
  }
***************
*** 130,136 ****
  bool DeltaOne(bool) (boolD.2002 bD.2111)
  [/home/manuel/pr48087.cc : 21:12] {
    struct BetaD.2084 D.2134;
!   intD.2 D.2173;
    struct AlphaD.2063 sD.2114;
    boolD.2002 b2D.2124;

--- 112,118 ----
  bool DeltaOne(bool) (boolD.2002 bD.2111)
  [/home/manuel/pr48087.cc : 21:12] {
    struct BetaD.2084 D.2134;
!   intD.2 D.2171;
    struct AlphaD.2063 sD.2114;
    boolD.2002 b2D.2124;

***************
*** 142,163 ****
        [/home/manuel/pr48087.cc : 20:26] # USE = anything 
        # CLB = anything 
        _ZN4BetaC1EvD.2093 ([/home/manuel/pr48087.cc : 20] &D.2134);
!       [/home/manuel/pr48087.cc : 20:26] try
!         {
!           [/home/manuel/pr48087.cc : 20:26] # USE = anything 
!           # CLB = anything 
!           b2D.2124 = _ZN4Beta5valueEvD.2091 ([/home/manuel/pr48087.cc : 20]
&D.2134);
!         }
!       finally
!         {
!           [/home/manuel/pr48087.cc : 20:18] # USE = anything 
!           # CLB = anything 
!           __comp_dtor D.2097 ([/home/manuel/pr48087.cc : 20] &D.2134);
!         }
!       [/home/manuel/pr48087.cc : 21:11] D.2173 = (intD.2) b2D.2124;
        [/home/manuel/pr48087.cc : 21:12] # USE = anything 
        # CLB = anything 
!       _Z5GammabD.2109 (D.2173);
      }
    finally
      {
--- 124,136 ----
        [/home/manuel/pr48087.cc : 20:26] # USE = anything 
        # CLB = anything 
        _ZN4BetaC1EvD.2093 ([/home/manuel/pr48087.cc : 20] &D.2134);
!       [/home/manuel/pr48087.cc : 20:26] # USE = anything 
!       # CLB = anything 
!       b2D.2124 = _ZN4Beta5valueEvD.2091 ([/home/manuel/pr48087.cc : 20]
&D.2134);
!       [/home/manuel/pr48087.cc : 21:11] D.2171 = (intD.2) b2D.2124;
        [/home/manuel/pr48087.cc : 21:12] # USE = anything 
        # CLB = anything 
!       _Z5GammabD.2109 (D.2171);
      }
    finally
      {

[Bug middle-end/48087] [4.5/4.6/4.7 Regression] -Wall -Werror adds warnings over and above those generated by -Wall

[paolo.carlini at oracle dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=48087

--- Comment #11 from Paolo Carlini <paolo.carlini at oracle dot com> 2011-10-18 23:42:43 UTC ---
Manuel, we need you help for some of these nasty diagnostic issues.

[Bug middle-end/48087] [4.5/4.6/4.7 Regression] -Wall -Werror adds warnings over and above those generated by -Wall

[manu at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=48087

--- Comment #12 from Manuel López-Ibáñez <manu at gcc dot gnu.org> 2011-10-19 01:44:12 UTC ---
I think the problem is the seen_error() test in gimple_push_cleanup. I am
guessing that it does some kind of "folding" that is skipped when an error has
been issued. There are two issues here:

1) Warnings converted to errors are not real errors, that is, the program is
still valid and we could in principle do whatever stuff we would do for a valid
program. We could do s/seen_error/seen_any_error/, and then add seen_real_error
(program_is_invalid). I bet most of the cases using seen_any_error, actually
mean program_is_invalid.

2) Whether even with real errors, we can fix the gimple generated by C++ to not
trigger the Wreturn-type warning. Or alternatively, make Wreturn-type more
intelligent to not emit a bogus warning here. The point here is that it is
perhaps possible to generate such a gimple from C++ that causes a bogus
warning. Currently, gimplify_push_cleanup "fixes" the bad gimple to avoid the
warning, but perhaps in other testcases, this "fix" doesn't trigger and we get
a bogus warning.

The thing is that even if we fix 1, we could probably trigger a real error
earlier and we end up with 2 (no inconsistency, but still bogus warning).

[Bug middle-end/48087] [4.5/4.6/4.7 Regression] -Wall -Werror adds warnings over and above those generated by -Wall

[rguenther at suse dot de]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=48087

--- Comment #13 from rguenther at suse dot de <rguenther at suse dot de> 2011-10-19 07:48:30 UTC ---
On Wed, 19 Oct 2011, manu at gcc dot gnu.org wrote:

> http://gcc.gnu.org/bugzilla/show_bug.cgi?id=48087
> 
> --- Comment #12 from Manuel López-Ibáñez <manu at gcc dot gnu.org> 2011-10-19 01:44:12 UTC ---
> I think the problem is the seen_error() test in gimple_push_cleanup. I am
> guessing that it does some kind of "folding" that is skipped when an error has
> been issued. There are two issues here:
> 
> 1) Warnings converted to errors are not real errors, that is, the program is
> still valid and we could in principle do whatever stuff we would do for a valid
> program. We could do s/seen_error/seen_any_error/, and then add seen_real_error
> (program_is_invalid). I bet most of the cases using seen_any_error, actually
> mean program_is_invalid.

I suppose that's reasonable.

[Bug middle-end/48087] [4.5/4.6/4.7 Regression] -Wall -Werror adds warnings over and above those generated by -Wall

[paolo.carlini at oracle dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=48087

--- Comment #14 from Paolo Carlini <paolo.carlini at oracle dot com> 2011-10-19 15:39:08 UTC ---
Thanks for explaining the seen_error mechanism, which I didn't know, but there
is something I still don't understand here. Consider PR49508 (I'm interested
because I opened it ;) : in that case we have only real errors, and then a
bugus warning. I don't see how fiddling with something at beginning of
gimple_push_cleanup could deal with such cases, and indeed if I hack it to
remove the early return, the warning triggers exactly in the same way. Or maybe
all this just indicated that  PR49508 really is a different issue, but I'm not
convinced...

[Bug middle-end/48087] [4.5/4.6/4.7 Regression] -Wall -Werror adds warnings over and above those generated by -Wall

[paolo.carlini at oracle dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=48087

--- Comment #15 from Paolo Carlini <paolo.carlini at oracle dot com> 2011-10-19 15:53:01 UTC ---
On this PR, removing the early return *works*, we have two non-bogus warnings
with -Wall and two errors with -Werror. Maybe we should really proceed one PR
at a time, re-open PR49508.

Now, in detail: do I understand correctly that you are proposing we would use
the new seen_real_errors *only* in gimple_push_cleanup? (at the moment I also
honestly don't know how to tell errors from warnings from real errors, but of
course can figure out myself)

[Bug middle-end/48087] [4.5/4.6/4.7 Regression] -Wall -Werror adds warnings over and above those generated by -Wall

[manu at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=48087

--- Comment #16 from Manuel López-Ibáñez <manu at gcc dot gnu.org> 2011-10-19 17:21:51 UTC ---
(In reply to comment #15)
> On this PR, removing the early return *works*, we have two non-bogus warnings
> with -Wall and two errors with -Werror. Maybe we should really proceed one PR
> at a time, re-open PR49508.

I agree. This is what I meant by (2) above. That the bogus warnings are somehow
hidden by gimple_push_cleanup, but it would be better to figure what 
gimple_push_clenaup is fixing and see whether it is possible to avoid
generating it in the first place. If it is the same issue as PR49508, then
fixing (1) is not enough.

> Now, in detail: do I understand correctly that you are proposing we would use
> the new seen_real_errors *only* in gimple_push_cleanup? (at the moment I also
> honestly don't know how to tell errors from warnings from real errors, but of
> course can figure out myself)

I would search where the counters are defined and add a new one for
real_errors. Then, for warnings converted to errors, do not increase the new
one. This should be a one-liner in diagnostic_report_diagnostic. Search for
diagnostic_kind_count. This would maintain seen_error working as it is now, but
one can define program_is_valid_p (or seen_real_error).

[Bug middle-end/48087] [4.5/4.6/4.7 Regression] -Wall -Werror adds warnings over and above those generated by -Wall

[paolo.carlini at oracle dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=48087

--- Comment #17 from Paolo Carlini <paolo.carlini at oracle dot com> 2011-10-19 17:27:36 UTC ---
Yeah, I was driving and it occurred to me too that we gonna need one more
counter... First, let's reopen the other bug. Thanks again for now.

[Bug middle-end/48087] [4.5/4.6/4.7 Regression] -Wall -Werror adds warnings over and above those generated by -Wall

[rguenth at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=48087

Richard Guenther <rguenth at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
   Target Milestone|---                         |4.5.4

[Bug middle-end/48087] [4.5/4.6/4.7 Regression] -Wall -Werror adds warnings over and above those generated by -Wall

[rguenth at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=48087

Richard Guenther <rguenth at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
           Priority|P3                          |P2

[Bug middle-end/48087] [4.5/4.6/4.7 Regression] -Wall -Werror adds warnings over and above those generated by -Wall

[paolo.carlini at oracle dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=48087

--- Comment #18 from Paolo Carlini <paolo.carlini at oracle dot com> 2011-10-27 10:20:29 UTC ---
Richard, the idea of adding another counter (per Comment #16) sounds good to
you? If we do that, the fix should be rather straightforward.

[Bug middle-end/48087] [4.5/4.6/4.7 Regression] -Wall -Werror adds warnings over and above those generated by -Wall

[rguenther at suse dot de]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=48087

--- Comment #19 from rguenther at suse dot de <rguenther at suse dot de> 2011-10-27 10:26:02 UTC ---
On Thu, 27 Oct 2011, paolo.carlini at oracle dot com wrote:

> http://gcc.gnu.org/bugzilla/show_bug.cgi?id=48087
> 
> --- Comment #18 from Paolo Carlini <paolo.carlini at oracle dot com> 2011-10-27 10:20:29 UTC ---
> Richard, the idea of adding another counter (per Comment #16) sounds good to
> you? If we do that, the fix should be rather straightforward.

I didn't investigate thorougly enough to give good advise here.

[Bug middle-end/48087] [4.5/4.6/4.7 Regression] -Wall -Werror adds warnings over and above those generated by -Wall

[rguenth at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=48087

--- Comment #20 from Richard Guenther <rguenth at gcc dot gnu.org> 2011-12-06 10:09:20 UTC ---
Looking again, I think that for warnings promoted to errors we should _not_
increase errorcount, but we should instead have a new global flag that
tells us whether there were any "real" errors, and check that in the
place that terminates compilation without producing assembler output.

[Bug middle-end/48087] [4.5/4.6/4.7/4.8 Regression] -Wall -Werror adds warnings over and above those generated by -Wall

[rguenth at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=48087

Richard Guenther <rguenth at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
   Target Milestone|4.5.4                       |4.6.4

--- Comment #21 from Richard Guenther <rguenth at gcc dot gnu.org> 2012-07-02 12:21:47 UTC ---
The 4.5 branch is being closed, adjusting target milestone.

[Bug middle-end/48087] [4.6/4.7/4.8 Regression] -Wall -Werror adds warnings over and above those generated by -Wall

[jakub at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=48087

--- Comment #22 from Jakub Jelinek <jakub at gcc dot gnu.org> 2013-01-15 15:11:40 UTC ---
Created attachment 29170
  --> http://gcc.gnu.org/bugzilla/attachment.cgi?id=29170
gcc48-pr48087.patch

Untested fix.  That said, it seems that on the provided testcase g++ already
generates the same set of warnings/errors for -Wreturn-type vs.
-Werror=return-type, starting with
http://gcc.gnu.org/viewcvs?root=gcc&view=rev&rev=186687
so supposedly you'd need to find a different testcase for this to still claim
4.8 Regression status.

Not sure if this can be stage4 material, I think it is more stage1-ish
material.

[Bug middle-end/48087] [4.6/4.7/4.8 Regression] -Wall -Werror adds warnings over and above those generated by -Wall

[manu at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=48087

--- Comment #23 from Manuel López-Ibáñez <manu at gcc dot gnu.org> 2013-01-15 16:39:22 UTC ---
(In reply to comment #22)
> Created attachment 29170 [details]
> gcc48-pr48087.patch
> 
> Untested fix.  That said, it seems that on the provided testcase g++ already
> generates the same set of warnings/errors for -Wreturn-type vs.
> -Werror=return-type, starting with
> http://gcc.gnu.org/viewcvs?root=gcc&view=rev&rev=186687
> so supposedly you'd need to find a different testcase for this to still claim
> 4.8 Regression status.
> 
> Not sure if this can be stage4 material, I think it is more stage1-ish
> material.

I think this hunk is not correct: 

--- gcc/cp/typeck.c.jj    2013-01-11 09:02:46.000000000 +0100
+++ gcc/cp/typeck.c    2013-01-15 15:35:47.216641020 +0100
@@ -7967,11 +7967,11 @@ convert_for_initialization (tree exp, tr
       int savew = 0, savee = 0;

       if (fndecl)
-    savew = warningcount, savee = errorcount;
+    savew = warningcount + werrorcount, savee = errorcount;
       rhs = initialize_reference (type, rhs, flags, complain);
       if (fndecl)
     {
-      if (warningcount > savew)
+      if (warningcount + werrorcount > savew)
         warning (0, "in passing argument %P of %q+D", parmnum, fndecl);
       else if (errorcount > savee)
         error ("in passing argument %P of %q+D", parmnum, fndecl);

since it will print:

error: something
warning: in passing argument

I think this should simply be an inform note like it is done in other cases (in
your own patch in gcc/cp/pt.c). 

This hunk also seems suspicious:

--- gcc/cp/call.c.jj    2013-01-11 09:02:46.000000000 +0100
+++ gcc/cp/call.c    2013-01-15 15:34:21.267155075 +0100
@@ -5709,12 +5709,12 @@ build_temp (tree expr, tree type, int fl
   int savew, savee;
   vec<tree, va_gc> *args;

-  savew = warningcount, savee = errorcount;
+  savew = warningcount + werrorcount, savee = errorcount;
   args = make_tree_vector_single (expr);
   expr = build_special_member_call (NULL_TREE, complete_ctor_identifier,
                     &args, type, flags, complain);
   release_tree_vector (args);
-  if (warningcount > savew)
+  if (warningcount + werrorcount > savew)
     *diagnostic_kind = DK_WARNING;
   else if (errorcount > savee)
     *diagnostic_kind = DK_ERROR;

I am not sure what for *diagnostic_kind is used, but it seems to change the
current behaviour (since a Werror will result in  *diagnostic_kind = DK_ERROR
before your patch).

[Bug middle-end/48087] [4.6/4.7/4.8/4.9 Regression] -Wall -Werror adds warnings over and above those generated by -Wall

[jakub at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=48087

--- Comment #24 from Jakub Jelinek <jakub at gcc dot gnu.org> 2013-03-21 20:02:55 UTC ---
Author: jakub
Date: Thu Mar 21 17:36:47 2013
New Revision: 196887

URL: http://gcc.gnu.org/viewcvs?rev=196887&root=gcc&view=rev
Log:
    PR middle-end/48087
    * diagnostic.def (DK_WERROR): New kind.
    * diagnostic.h (werrorcount): Define.
    * diagnostic.c (diagnostic_report_diagnostic): For DK_WARNING
    promoted to DK_ERROR, increment DK_WERROR counter instead of
    DK_ERROR counter.
    * toplev.c (toplev_main): Call print_ignored_options even if
    just werrorcount is non-zero.  Exit with FATAL_EXIT_CODE
    even if just werrorcount is non-zero.

    * pt.c (convert_nontype_argument): Count werrorcount as warnings.
    * call.c (build_temp): Likewise.
    * method.c (synthesize_method): Likewise.
    * typeck.c (convert_for_initialization): Likewise.

Modified:
    trunk/gcc/ChangeLog
    trunk/gcc/cp/ChangeLog
    trunk/gcc/cp/call.c
    trunk/gcc/cp/method.c
    trunk/gcc/cp/pt.c
    trunk/gcc/cp/typeck.c
    trunk/gcc/diagnostic.c
    trunk/gcc/diagnostic.def
    trunk/gcc/diagnostic.h
    trunk/gcc/toplev.c

[Bug middle-end/48087] [4.7/4.8/4.9 Regression] -Wall -Werror adds warnings over and above those generated by -Wall

[jakub at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=48087

Jakub Jelinek <jakub at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
   Target Milestone|4.6.4                       |4.7.4

--- Comment #25 from Jakub Jelinek <jakub at gcc dot gnu.org> 2013-04-12 15:17:13 UTC ---
GCC 4.6.4 has been released and the branch has been closed.

[Bug middle-end/48087] [4.7/4.8/4.9 Regression] -Wall -Werror adds warnings over and above those generated by -Wall

[law at redhat dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=48087

Jeffrey A. Law <law at redhat dot com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|NEW                         |RESOLVED
                 CC|                            |law at redhat dot com
         Resolution|---                         |FIXED

--- Comment #26 from Jeffrey A. Law <law at redhat dot com> ---
Fixed long ago on the trunk.