[Bug c++/20423] Warning -Woverloaded-virtual triggers to often

[Bug c++/20423] Warning -Woverloaded-virtual triggers to often

[gdr at gcc dot gnu dot org]

------- Comment #4 from gdr at gcc dot gnu dot org  2005-11-24 02:23 -------
Agreed with the reporter's analysis


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gdr at gcc dot gnu dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |NEW
     Ever Confirmed|0                           |1
   Last reconfirmed|0000-00-00 00:00:00         |2005-11-24 02:23:45
               date|                            |


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=20423

[Bug c++/20423] Warning -Woverloaded-virtual triggers to often

[manu at gcc dot gnu dot org]

------- Comment #5 from manu at gcc dot gnu dot org  2007-02-14 22:30 -------
I am looking at this but it is a bit hard to see how to make the distinction
between the two kinds. I don't want to introduce yet another loop in
warn_hidden but perhaps that is unavoidable. Any hints?


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=20423

[Bug c++/20423] Warning -Woverloaded-virtual triggers to often

[manu at gcc dot gnu dot org]

------- Comment #6 from manu at gcc dot gnu dot org  2007-02-16 10:01 -------
A really wild-guess patch. Comments?


Index: gcc/cp/class.c
===================================================================
--- gcc/cp/class.c      (revision 121953)
+++ gcc/cp/class.c      (working copy)
@@ -2377,6 +2377,8 @@ warn_hidden (tree t)
       tree binfo;
       int j;

+      bool just_hidden = false;
+
       /* All functions in this slot in the CLASSTYPE_METHOD_VEC will
         have the same name.  Figure out what name that is.  */
       name = DECL_NAME (OVL_CURRENT (fns));
@@ -2408,8 +2410,14 @@ warn_hidden (tree t)
                /* If the method from the base class has the same
                   signature as the method from the derived class, it
                   has been overridden.  */
-               if (same_signature_p (fndecl, TREE_VALUE (*prev)))
-                 *prev = TREE_CHAIN (*prev);
+               if (same_signature_p (fndecl, TREE_VALUE (*prev)))
+                 {
+                   *prev = TREE_CHAIN (*prev);
+                   /* If at least one method has the same signature,
+                      the not overloaded variants are just
+                      hidden.  */
+                   just_hidden = true;
+                 }
                else
                  prev = &TREE_CHAIN (*prev);
            }
@@ -2419,9 +2427,17 @@ warn_hidden (tree t)
         as they are hidden.  */
       while (base_fndecls)
        {
-         /* Here we know it is a hider, and no overrider exists.  */
-         warning (0, "%q+D was hidden", TREE_VALUE (base_fndecls));
-         warning (0, "  by %q+D", fns);
+         /* If Here we know it is a hider, and no overrider exists.  */
+         if (just_hidden)
+           {
+             warning (OPT_Wpartial_overloaded_virtual, "%q+D was hidden",
TREE_VALUE (base_fndecls));
+             warning (OPT_Wpartial_overloaded_virtual, "  by %q+D", fns);
+           }                                                                   
+         else
+           {
+             warning (OPT_Woverloaded_virtual, "%q+D was hidden", TREE_VALUE
(base_fndecls));
+             warning (OPT_Woverloaded_virtual, "  by %q+D", fns);
+           }
          base_fndecls = TREE_CHAIN (base_fndecls);
        }
     }


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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=20423

[Bug c++/20423] Warning -Woverloaded-virtual triggers to often

[Woebbeking at web dot de]

------- Comment #7 from Woebbeking at web dot de  2008-11-30 15:36 -------
Any progress on this? 

This warning could be really useful if only 1) would be handled. In its current
state I can't use it as I get too many "false" positives :-(


-- 

Woebbeking at web dot de changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |Woebbeking at web dot de


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=20423

[Bug c++/20423] Warning -Woverloaded-virtual triggers to often

[jason at gcc dot gnu dot org]

-- 

jason at gcc dot gnu dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
         AssignedTo|unassigned at gcc dot gnu   |jason at gcc dot gnu dot org
                   |dot org                     |
             Status|NEW                         |ASSIGNED
           Keywords|                            |patch
   Last reconfirmed|2005-11-24 02:23:45         |2009-07-17 10:00:52
               date|                            |


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=20423

[Bug c++/20423] Warning -Woverloaded-virtual triggers to often

[jason at gcc dot gnu dot org]

------- Comment #8 from jason at gcc dot gnu dot org  2009-07-18 06:10 -------
An old patch: http://gcc.gnu.org/ml/gcc-patches/1999-03n/msg00182.html


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=20423

[Bug c++/20423] Warning -Woverloaded-virtual triggers to often

[jwakely dot gcc at gmail dot com]

------- Comment #9 from jwakely dot gcc at gmail dot com  2009-07-21 17:36 -------
(In reply to comment #0)
> 
> This is also not conforming to the "specification" in
> http://gcc.gnu.org/ml/gcc-bugs/1999-08n/msg01069.html
> 
>   Warn when a derived class function declaration may be an error in
>   defining a virtual function.  In a derived class, the definitions of
>   virtual functions must match the type signature of a virtual
>   function declared in the base class.  With this option, the compiler
>   warns when you define a function with the same name as a virtual
>   function, but with a type signature that does not match any
>   declarations from the base class.

But that's not what it does. The description in the manual describes the
current behaviour correctly, that description above doesn't.

(In reply to comment #6)
> A really wild-guess patch. Comments?
...
> +                   /* If at least one method has the same signature,
> +                      the not overloaded variants are just
> +                      hidden.  */
> +                   just_hidden = true;

Shouldn't this say "not overridden variants" ?

I don't like the name -Wpartial-overloaded-virtual for the same reason. The
name should clearly distinguish whether it is triggered by overloading,
overriding or hiding.

-Woverloaded-virtual is a reasonable name for the current behaviour; it
triggers if there is an overload that hides a virtual (whether the overload is
itself virtual or not.)  The proposed -Wpartial-overloaded-virtual name makes
no sense.


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=20423

[Bug c++/20423] Warning -Woverloaded-virtual triggers to often

[jwakely dot gcc at gmail dot com]

------- Comment #10 from jwakely dot gcc at gmail dot com  2009-08-11 14:24 -------
as with bug 31937, there is overlap between this enhancement and the 'Explicit
Virtual Function Overrides' paper,
http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2009/n2928.htm

the attributes proposed in that paper allow the derived class to explicitly
state whether a function should override or hide the same name in the base
class, making it ill-formed if there is unintended hiding


-- 

jwakely dot gcc at gmail dot com changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |jwakely dot gcc at gmail dot
                   |                            |com


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=20423

[Bug c++/20423] Warning -Woverloaded-virtual triggers to often

[jason at gcc dot gnu dot org]

------- Comment #11 from jason at gcc dot gnu dot org  2010-02-19 21:23 -------
Not working on this now.


-- 

jason at gcc dot gnu dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
         AssignedTo|jason 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=20423

[Bug c++/20423] Warning -Woverloaded-virtual triggers to often

[jason at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=20423

Jason Merrill <jason at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
   Target Milestone|---                         |13.0
         Resolution|---                         |FIXED
             Status|ASSIGNED                    |RESOLVED

--- Comment #13 from Jason Merrill <jason at gcc dot gnu.org> ---
For GCC 13 the requested semantics will be available in -Woverloaded-virtual=1
or -Wall.

[Bug c++/20423] Warning -Woverloaded-virtual triggers to often

[cvs-commit at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=20423

--- Comment #12 from CVS Commits <cvs-commit at gcc dot gnu.org> ---
The master branch has been updated by Jason Merrill <jason@gcc.gnu.org>:

https://gcc.gnu.org/g:113844d68e94f4e9c0e946db351ba7d3d4a1335a

commit r13-1262-g113844d68e94f4e9c0e946db351ba7d3d4a1335a
Author: Jason Merrill <jason@redhat.com>
Date:   Fri Jun 24 14:40:12 2022 -0400

    c++: Include -Woverloaded-virtual in -Wall [PR87729]

    This seems like a good warning to have in -Wall, as requested.  But as
    pointed out in PR20423, some users want a warning only when a derived
    function doesn't override any base function.  So let's put that lesser
    version in -Wall (and -Woverloaded-virtual=1) while leaving the semantics
    for the existing option the same.

            PR c++/87729
            PR c++/20423

    gcc/c-family/ChangeLog:

            * c.opt (Woverloaded-virtual): Add levels, include in -Wall.

    gcc/ChangeLog:

            * doc/invoke.texi: Document changes.

    gcc/cp/ChangeLog:

            * class.cc (warn_hidden): Handle -Woverloaded-virtual=1.

    gcc/testsuite/ChangeLog:

            * g++.dg/warn/Woverloaded-virt1.C: New test.
            * g++.dg/warn/Woverloaded-virt2.C: New test.

[Bug c++/20423] Warning -Woverloaded-virtual triggers to often

[jason at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=20423

Jason Merrill <jason at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |jason at gcc dot gnu.org
             Status|NEW                         |ASSIGNED
           Assignee|unassigned at gcc dot gnu.org      |jason at gcc dot gnu.org

[Bug c++/20423] Warning -Woverloaded-virtual triggers to often

[pinskia at gcc dot gnu dot org]

------- Additional Comments From pinskia at gcc dot gnu dot org  2005-03-29 14:10 -------
*** Bug 20683 has been marked as a duplicate of this bug. ***

-- 
           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |oliverst at online dot de


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=20423

[Bug c++/20423] Warning -Woverloaded-virtual triggers to often

[micis at gmx dot de]

------- Additional Comments From micis at gmx dot de  2005-03-11 17:30 -------
I think there a two different situations:

1) in the derived class you define a method with the same name but
   different parameters. 

This is typically a serious bug in your program which can result in the 
exectution of the code of the wrong (not overloaded) function.


2) in the derived class you define not all overloaded variants. 

In that case the not overloaded variants are hidden but no run-time-error 
occurs. If you try to call a hidden variant, the compiler complains.


If "-Woverloaded-virtual" only triggers in case 1, it could be enabled
with "-Wall" as it typically indicates a severe bug in your program.

If there would be a "-Wpartial-overloaded-virtual" you could enable if you like 
it and you can. I have to work with a large existing code basis where I would 
not enable it.

I think to give different messages like ICC is the way to go.

Michael Cieslinski


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=20423

[Bug c++/20423] Warning -Woverloaded-virtual triggers to often

[pinskia at gcc dot gnu dot org]

------- Additional Comments From pinskia at gcc dot gnu dot org  2005-03-11 15:11 -------
Hmm, ICC gives:
t.cc(7): warning #654: overloaded virtual function "Foo::Func" is only partially overridden in class "Baz"
  class Baz: public Foo
        ^

t.cc(14): error #165: too few arguments in function call
    b->Func(1);
             ^

compilation aborted for t.cc (code 2)

The warning is correct because Func(int) is still hidden in the supper class and you cannot use it:
class Foo
{
public: virtual void Func(int);
        virtual void Func(int, int);
};

class Baz: public Foo
{
public: virtual void Func(int, int);
};

void g(Baz *b)
{
  b->Func(1);
}


Maybe we should do the warning which ICC is giving instead of the one which we give right now.

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


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=20423