[Bug c++/28774] New: Request for warning where const/volatile is ignored in a cast

[Bug c++/28774] New: Request for warning where const/volatile is ignored in a cast

[simon_baldwin at yahoo dot com]

In the code fragment

  int i = static_cast<const int>(1.234);
  int j = static_cast<volatile int>(1.234);

the const and volatile qualifiers in the cast are silently ignored, even with
-Wall -W -pedantic.  A warning from g++ for this mild infraction would be
useful.


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           Summary: Request for warning where const/volatile is ignored in a
                    cast
           Product: gcc
           Version: 4.1.0
            Status: UNCONFIRMED
          Severity: enhancement
          Priority: P3
         Component: c++
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: simon_baldwin at yahoo dot com


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=28774

[Bug c++/28774] Request for warning where const/volatile is ignored in a cast

[bangerth at dealii dot org]

------- Comment #1 from bangerth at dealii dot org  2006-08-24 01:59 -------
Um, why? The value "1.234" is an rvalue of type double. You cast it to
an rvalue of type "const int", which can clearly be assigned to an
int right away without another cast. In fact, const-volatile qualifications
do not have meaning for rvalues at all, which makes the whole question
kinda moot. 

Or do I miss something?

W.


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bangerth at dealii dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |bangerth at dealii dot org
             Status|UNCONFIRMED                 |WAITING


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=28774

[Bug c++/28774] Request for warning where const/volatile is ignored in a cast

[simon_baldwin at yahoo dot com]

------- Comment #2 from simon_baldwin at yahoo dot com  2006-08-24 16:53 -------
You didn't miss anything.  There's no bug here, just a request for a new
warning message.

As you note, the const-volatile qualifications in the cast have no meaning, and
are completely ignored by the compiler.  While it's busy ignoring them, it
could note this as a warning, in case the code author really meant something
different.

icc warns here; this PR aims to improve agreement in warnings between g++ and
icc.


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=28774

[Bug c++/28774] Request for warning where const/volatile is ignored in a cast

[pinskia at gcc dot gnu dot org]

------- Comment #3 from pinskia at gcc dot gnu dot org  2006-08-27 05:03 -------
(In reply to comment #2)
> icc warns here; this PR aims to improve agreement in warnings between g++ and
> icc.
> 

HUH? Why do you want that?  GCC warns in more places than ICC will ever warn. 
To me this is an useless warning and in fact goes against what is questionable
even to a standards guy.


-- 

pinskia at gcc dot gnu dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|WAITING                     |RESOLVED
         Resolution|                            |INVALID


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=28774

[Bug c++/28774] Request for warning where const/volatile is ignored in a cast

[ian at airs dot com]

------- Comment #4 from ian at airs dot com  2006-08-27 06:44 -------
I disagree.  It is always useful to optionally warn about meaningless code.  It
can be a way to find a real bug in the program.  It is not conceptually
different from existing warnings like -Wredundant-decls.  The code works fine,
but something is odd.

The behaviour of icc is irrelevant here.  If you want to close this again,
please give a reason why we should not warn about meaningless code.


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ian at airs dot com changed:

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


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=28774

[Bug c++/28774] Request for warning where const/volatile is ignored in a cast

[manu at gcc dot gnu dot org]

------- Comment #5 from manu at gcc dot gnu dot org  2007-01-23 14:35 -------
We already have a warning about discarding qualifiers somewhere. Perhaps we
could just add this to that one (saving us from yet another warning option).


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manu at gcc dot gnu dot org changed:

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


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=28774

[Bug c++/28774] Request for warning where const/volatile is ignored in a cast

[manu at gcc dot gnu dot org]

------- Comment #6 from manu at gcc dot gnu dot org  2007-03-12 12:10 -------
This seems a duplicate of PR 14710.


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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=28774

[Bug c++/28774] Request for warning where const/volatile is ignored in a cast

[simon_baldwin at yahoo dot com]

------- Comment #7 from simon_baldwin at yahoo dot com  2007-03-12 21:48 -------
PR 14710 isn't really quite the same thing as PR 28774.  PR 14170 is concerned
with unnecessary casts; PR 28774 is concerned with unnecessary "const" or
"volatile" qualifiers within otherwise valid and perhaps necessary casts.

That said, this PR really isn't all that useful, is tiny, and hasn't received a
lot of support, so I'm going to withdraw it (by setting resolution to
"WONTFIX", which I hope will do the right thing).


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simon_baldwin at yahoo dot com changed:

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


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=28774