[Bug c++/12242] g++ should warn about out-of-range int->enum conversions

[Bug c++/12242] g++ should warn about out-of-range int->enum conversions

[gdr at gcc dot gnu dot org]

------- Comment #6 from gdr at gcc dot gnu dot org  2006-01-23 01:20 -------
Working on a patch.


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gdr at gcc dot gnu dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |gdr at gcc dot gnu dot org
         AssignedTo|unassigned at gcc dot gnu   |gdr at gcc dot gnu dot org
                   |dot org                     |
             Status|NEW                         |ASSIGNED
   Last reconfirmed|2005-12-11 23:27:30         |2006-01-23 01:20:08
               date|                            |


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=12242

[Bug c++/12242] g++ should warn about out-of-range int->enum conversions

[lopezibanez at gmail dot com]

------- Comment #7 from lopezibanez at gmail dot com  2006-07-08 18:33 -------
(In reply to comment #6)
> Working on a patch.
> 

Hi Gabriel, what is your patch going to do? Is it going to emit a warning?
Would it be appropriate to emit the same warning for the C front end?


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lopezibanez at gmail dot com changed:

           What    |Removed                     |Added
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                 CC|                            |lopezibanez at gmail dot com


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=12242

[Bug c++/12242] g++ should warn about out-of-range int->enum conversions

[manu at gcc dot gnu dot org]

------- Comment #8 from manu at gcc dot gnu dot org  2007-01-21 17:47 -------
I was thinking about adding this to Wconversion. But perhaps it is more
appropriate for Wundefined. After all, the value may change or not depending on
the particular implementation, since it is undefined. 

Gabriel, should I add it to the list of Wundefined?


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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=12242

[Bug c++/12242] g++ should warn about out-of-range int->enum conversions

[manu at gcc dot gnu dot org]

------- Comment #9 from manu at gcc dot gnu dot org  2008-02-15 11:09 -------
(In reply to comment #0)
> enum E { A };
> ...
> E e = static_cast<E> (10);
> 
> Yes, i know that result of this is undefined.

Is this true? I haven't found any mention of this.

> However, previous versions of g++ (and every other c++ compiler i've used)
> has implemented this in what seems like the simplest way: the compiler
> simply assigns the value `10' to the enum value, regardless of the
> fact that this is not a valid value for the enum.

We assing 10 in GCC 4.3.

> Therefore, the compiler is silently changing the behavior of the
> code from what was likely intended.  So i think a warning would
> be appropriate in this situation.  The current verison of 3.4 does
> not issue any warning, even with `-Wall -pedantic'.

The following patch implements the warning for this testcase. Do you know other
cases that may be interesting to warn about?

Index: gcc/testsuite/g++.dg/warn/pr12242.C
===================================================================
--- gcc/testsuite/g++.dg/warn/pr12242.C (revision 0)
+++ gcc/testsuite/g++.dg/warn/pr12242.C (revision 0)
@@ -0,0 +1,4 @@
+// { dg-do compile }
+// { dg-options "-Wall -Wextra -Wconversion" }
+enum E { A };
+E e = static_cast<E> (10); // { dg-warning "warning.*undefined" }
Index: gcc/cp/typeck.c
===================================================================
--- gcc/cp/typeck.c     (revision 132310)
+++ gcc/cp/typeck.c     (working copy)
@@ -5069,10 +5069,15 @@ build_static_cast_1 (tree type, tree exp
      types which are integral, floating, or enumeration types can be
      performed.  */
   if ((INTEGRAL_TYPE_P (type) || SCALAR_FLOAT_TYPE_P (type))
       && (INTEGRAL_TYPE_P (intype) || SCALAR_FLOAT_TYPE_P (intype)))
     {
+      if (TREE_CODE (expr) == INTEGER_CST
+         && TREE_CODE (type) == ENUMERAL_TYPE
+         && !int_fits_type_p (expr, type))
+       warning (0, "this conversion is undefined");
+
       expr = ocp_convert (type, expr, CONV_C_CAST, LOOKUP_NORMAL);

       /* Ignore any integer overflow caused by the cast.  */
       expr = ignore_overflows (expr, orig);
       return expr;


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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=12242

[Bug c++/12242] g++ should warn about out-of-range int->enum conversions

[pinskia at gcc dot gnu dot org]

------- Comment #10 from pinskia at gcc dot gnu dot org  2008-02-15 11:15 -------
> Is this true? I haven't found any mention of this.
It is at least unspecified.


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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=12242

[Bug c++/12242] g++ should warn about out-of-range int->enum conversions

[manu at gcc dot gnu dot org]

------- Comment #11 from manu at gcc dot gnu dot org  2008-02-15 11:32 -------
(In reply to comment #10)
> > Is this true? I haven't found any mention of this.
> It is at least unspecified.
> 

So warning makes sense then, doesn't it? But perhaps the wording is not ideal.


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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=12242

[Bug c++/12242] g++ should warn about out-of-range int->enum conversions

[rguenth at gcc dot gnu dot org]

------- Comment #12 from rguenth at gcc dot gnu dot org  2008-02-15 11:34 -------
It should probably say that it will truncate the value, which is what will
happen.


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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=12242

[Bug c++/12242] g++ should warn about out-of-range int->enum conversions

[manu at gcc dot gnu dot org]

------- Comment #13 from manu at gcc dot gnu dot org  2008-02-15 11:42 -------
(In reply to comment #12)
> It should probably say that it will truncate the value, which is what will
> happen.
> 

That doesn't happen. The result of the conversion is 10 in GCC 4.3. It seems it
doesn't need to be 10 and it wasn't 10 in 3.4. I don't want to get a PR saying
"the warning says that the value is truncated but I printed it and it is not
truncated! the warning is wrong! what a crappy compiler!". So better say that
whatever may happen in a formal way.


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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=12242

[Bug c++/12242] g++ should warn about out-of-range int->enum conversions

[bangerth at dealii dot org]

------- Comment #14 from bangerth at dealii dot org  2008-08-07 05:41 -------
Patch now here:
  http://gcc.gnu.org/ml/gcc-patches/2008-08/msg00436.html


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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=12242

[Bug c++/12242] g++ should warn about out-of-range int->enum conversions

[bangerth at dealii dot org]

------- Comment #15 from bangerth at dealii dot org  2008-08-07 05:41 -------
Hi Manu,
just saw your patch for PR 12242 and have a comment: I believe the warning
message would be much better if it said *why* the result is unspecified (if the
expression being cast is a bit more complicated then it may not be immediately
clear to the casual observer that the reason is that the value is out of range;
one could also think that for whatever reason conversions between enums are
unspecified -- which of course isn't the true reason).

So I think a better wording would be
+       warning (OPT_Wconversion, 
+                "the result of %<static_cast<%T>(%E)%> is unspecified because
the " 
+               "value is out of range for type %T",
+                type, expr, type);

Best
  Wolfgang


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bangerth at dealii dot org changed:

           What    |Removed                     |Added
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                 CC|                            |bangerth at dealii dot org


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=12242

[Bug c++/12242] g++ should warn about out-of-range int->enum conversions

[manu at gcc dot gnu dot org]

------- Comment #16 from manu at gcc dot gnu dot org  2008-08-07 07:50 -------
The expression cannot be very complicated because it needs to be a INTEGER_CST.
On the other hand, I agree that it is best to give users as much information as
reasonable. I think it is better if you comment in gcc-patches so reviewers can
see your proposal. I would prefer to not repeat twice %T, though. Also, I think
users are going to have trouble to understand that the range of the enumeral is
larger than the number of enumerators it contains. Perhaps we should print the
range of %T?

"the result of %<static_cast%> is unspecified because %qE is outside the range
[%d,%d] of type %qT."


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manu at gcc dot gnu dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
         AssignedTo|gdr at gcc dot gnu dot org  |manu at gcc dot gnu dot org


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=12242

[Bug c++/12242] g++ should warn about out-of-range int->enum conversions

[bangerth at dealii dot org]

------- Comment #17 from bangerth at dealii dot org  2008-08-07 13:13 -------
(In reply to comment #16)
> The expression cannot be very complicated because it needs to be a INTEGER_CST.

Sure, but it can be of the form
   ~SOME_PREPROCESSOR_MACRO | (MACRO2 ^ MACRO3)
What I meant to say is that the value of the expression may not be
obvious to the author of the code.


> On the other hand, I agree that it is best to give users as much information as
> reasonable. I think it is better if you comment in gcc-patches so reviewers can
> see your proposal.

Will do next time, I guess for this time we're stuck here :-)


> I would prefer to not repeat twice %T, though. Also, I think
> users are going to have trouble to understand that the range of the enumeral is
> larger than the number of enumerators it contains. Perhaps we should print the
> range of %T?
> 
> "the result of %<static_cast%> is unspecified because %qE is outside the range
> [%d,%d] of type %qT."

That would be an excellent idea as well.

Thanks
 Wolfgang


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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=12242

[Bug c++/12242] g++ should warn about out-of-range int->enum conversions

[manu at gcc dot gnu dot org]

------- Comment #18 from manu at gcc dot gnu dot org  2008-08-09 00:32 -------
Subject: Bug 12242

Author: manu
Date: Sat Aug  9 00:30:41 2008
New Revision: 138898

URL: http://gcc.gnu.org/viewcvs?root=gcc&view=rev&rev=138898
Log:
2008-08-09  Manuel Lopez-Ibanez  <manu@gcc.gnu.org>

        PR c++/12242
cp/
        * cvt.c (ocp_convert): Warn for out-of-range conversions to enum.

testsuite/
        * g++.dg/warn/pr12242.C: New.

Added:
    trunk/gcc/testsuite/g++.dg/warn/pr12242.C
Modified:
    trunk/gcc/cp/ChangeLog
    trunk/gcc/cp/cvt.c
    trunk/gcc/testsuite/ChangeLog


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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=12242

[Bug c++/12242] g++ should warn about out-of-range int->enum conversions

[manu at gcc dot gnu dot org]

------- Comment #19 from manu at gcc dot gnu dot org  2008-08-09 00:35 -------
FIXED in GCC 4.4


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manu at gcc dot gnu dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|ASSIGNED                    |RESOLVED
         Resolution|                            |FIXED
   Target Milestone|---                         |4.4.0


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=12242

[Bug c++/12242] g++ should warn about out-of-range int->enum conversions

[pinskia at gcc dot gnu dot org]

-- 
           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |pinskia at gcc dot gnu dot
                   |                            |org
   Last reconfirmed|2004-11-13 05:46:53         |2005-02-12 23:23:46
               date|                            |


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=12242

[Bug c++/12242] g++ should warn about out-of-range int->enum conversions

[pinskia at gcc dot gnu dot org]

------- Additional Comments From pinskia at gcc dot gnu dot org  2004-08-13 23:45 -------
*** Bug 17022 has been marked as a duplicate of this bug. ***

-- 
           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |igodard at pacbell dot net


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=12242

[Bug c++/12242] g++ should warn about out-of-range int->enum conversions

[pinskia at gcc dot gnu dot org]

-- 
           What    |Removed                     |Added
----------------------------------------------------------------------------
           Keywords|                            |diagnostic
   Last reconfirmed|2003-09-10 23:10:38         |2003-12-06 08:22:34
               date|                            |


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=12242

[Bug c++/12242] g++ should warn about out-of-range int->enum conversions

[bangerth at dealii 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=12242


bangerth at dealii dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |mueller at kde dot org


------- Additional Comments From bangerth at dealii dot org  2003-09-10 23:11 -------
*** Bug 11749 has been marked as a duplicate of this bug. ***

[Bug c++/12242] g++ should warn about out-of-range int->enum conversions

[bangerth at dealii 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=12242


bangerth at dealii dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |NEW
     Ever Confirmed|                            |1
   Last reconfirmed|0000-00-00 00:00:00         |2003-09-10 23:10:38
               date|                            |


------- Additional Comments From bangerth at dealii dot org  2003-09-10 23:10 -------
Legitimate, so confirmed.

[Bug c++/12242] g++ should warn about out-of-range int->enum conversions

[bangerth at dealii 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=12242


bangerth at dealii dot org changed:

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


------- Additional Comments From bangerth at dealii dot org  2003-09-10 23:10 -------
Let's turn this around. This PR has much more information than the other one 
so let's keep it open and redirect the other one. 
 
W.

[Bug c++/12242] g++ should warn about out-of-range int->enum conversions

[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=12242


pinskia at gcc dot gnu dot org changed:

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


------- Additional Comments From pinskia at gcc dot gnu dot org  2003-09-10 22:30 -------
This is a dup of bug 11749.

*** This bug has been marked as a duplicate of 11749 ***