[Bug c++/18468] New: bad code in template function called from template class method

[Bug c++/18468] New: bad code in template function called from template class method

[james_avera at yahoo dot com]

A template function (which swaps two values)
is called in a loop in an inlined method of a template class.  The number
of loop iterations is a constant, so the compiler might be trying to unroll
the loop.

The final assignment of the swap function is not executed after the
first iteration, causing incorrect results.

The problem occurs with -O2 or -O3, but not with -O.

I will attach a self-contained demo program.

-- 
           Summary: bad code in template function called from template class
                    method
           Product: gcc
           Version: 3.3.3
            Status: UNCONFIRMED
          Severity: normal
          Priority: P2
         Component: c++
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: james_avera at yahoo dot com
                CC: gcc-bugs at gcc dot gnu dot org
 GCC build triplet: i586-suse-linux-gnu
  GCC host triplet: i586-suse-linux-gnu
GCC target triplet: i586-suse-linux-gnu


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=18468

[Bug c++/18468] bad code in template function called from template class method

[james_avera at yahoo dot com]

------- Additional Comments From james_avera at yahoo dot com  2004-11-13 20:32 -------
Created an attachment (id=7542)
 --> (http://gcc.gnu.org/bugzilla/attachment.cgi?id=7542&action=view)
test case

Please compile with -O2

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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=18468

[Bug c++/18468] bad code in template function called from template class method

[pinskia at gcc dot gnu dot org]

------- Additional Comments From pinskia at gcc dot gnu dot org  2004-11-13 20:37 -------
You are violating the C++ aliasing rules:

class GetPtrtokeyFunctor {
    public: 
    const PtrInt * operator()(const Objptr & objptr)
            { return reinterpret_cast<const PtrInt *>(&objptr); }
};



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


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=18468

[Bug c++/18468] bad code in template function called from template class method

[james_avera at yahoo dot com]

------- Additional Comments From james_avera at yahoo dot com  2004-11-16 02:47 -------
Subject: Re:  bad code in template function called from template class method

Hi,
Can you summarize what aliasing rule is violated?

Note that the argument is a ref, so the code is
not taking the adderess of a temporary.

Thanks,
-Jim

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

> 
> ------- Additional Comments From pinskia at gcc dot gnu dot org 
> 2004-11-13 20:37 -------
> You are violating the C++ aliasing rules:
> 
> class GetPtrtokeyFunctor {
>     public: 
>     const PtrInt * operator()(const Objptr & objptr)
>             { return reinterpret_cast<const PtrInt *>(&objptr); }
> };
> 
> 
> 
> -- 
>            What    |Removed                     |Added
>
----------------------------------------------------------------------------
>              Status|UNCONFIRMED                 |RESOLVED
>          Resolution|                            |INVALID
> 
> 
> http://gcc.gnu.org/bugzilla/show_bug.cgi?id=18468
> 
> ------- You are receiving this mail because: -------
> You reported the bug, or are watching the reporter.
> 


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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=18468

[Bug c++/18468] bad code in template function called from template class method

[pinskia at gcc dot gnu dot org]

------- Additional Comments From pinskia at gcc dot gnu dot org  2004-11-16 02:52 -------
Read http://gcc.gnu.org/bugs.html#nonbugs_general

Casting does not work as expected when optimization is turned on.

-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=18468

[Bug c++/18468] bad code in template function called from template class method

[pinskia at gcc dot gnu dot org]

------- Additional Comments From pinskia at gcc dot gnu dot org  2005-06-05 09:04 -------
Reopening to ...

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


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=18468

[Bug c++/18468] bad code in template function called from template class method

[pinskia at gcc dot gnu dot org]

------- Additional Comments From pinskia at gcc dot gnu dot org  2005-06-05 09:04 -------
Mark as a dup of bug 21920

*** This bug has been marked as a duplicate of 21920 ***

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


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=18468