[Bug c++/41368] New: Erroneous aliasing rules violation messages are issued

[Bug c++/41368] New: Erroneous aliasing rules violation messages are issued

[yuri at tsoft dot com]

When the attached testcase is compiled with gcc-4.4.1 there are two aliasing
error messages issued, that appear to be wrong.


-- 
           Summary: Erroneous aliasing rules violation messages are issued
           Product: gcc
           Version: 4.4.1
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: yuri at tsoft dot com


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=41368

[Bug c++/41368] Erroneous aliasing rules violation messages are issued

[yuri at tsoft dot com]

------- Comment #1 from yuri at tsoft dot com  2009-09-16 05:12 -------
Created an attachment (id=18593)
 --> (http://gcc.gnu.org/bugzilla/attachment.cgi?id=18593&action=view)
testcase

command line: g++ -c -O5 -Wall pr.C


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=41368

[Bug c++/41368] Erroneous aliasing rules violation messages are issued

[yuri at tsoft dot com]

------- Comment #2 from yuri at tsoft dot com  2009-09-16 05:17 -------
gcc-4.3.1 didn't issue such warnings.

I wasn't able to minimize the testcase more.
Somehow if eee instance of Zzzzz is removed and just Fffff::bbb() is called
messages disappear. This is strange since code around lines in question is all
the same in both cases.


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=41368

[Bug c++/41368] Erroneous aliasing rules violation messages are issued

[rguenth at gcc dot gnu dot org]

------- Comment #3 from rguenth at gcc dot gnu dot org  2009-09-16 08:02 -------
The compiler warns for the store in

  D.1845_1 = (struct Fffff *) &eee.llll[0];
  D.1854_8 ={v} &0B->D.1740.rrrr[0];
  D.1845_1->ppp1 = D.1854_8;

because that stores to eee.llll (type char) via a pointer to type Fffff which
is invalid.


-- 

rguenth at gcc dot gnu dot org changed:

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


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=41368

[Bug c++/41368] Erroneous aliasing rules violation messages are issued

[yuri at rawbw dot com]

------- Comment #4 from yuri at rawbw dot com  2009-09-16 09:55 -------
Subject: Re:  Erroneous aliasing rules violation messages are
 issued

rguenth at gcc dot gnu dot org wrote:
> ------- Comment #3 from rguenth at gcc dot gnu dot org  2009-09-16 08:02 -------
> The compiler warns for the store in
>
>   D.1845_1 = (struct Fffff *) &eee.llll[0];
>   D.1854_8 ={v} &0B->D.1740.rrrr[0];
>   D.1845_1->ppp1 = D.1854_8;
>
> because that stores to eee.llll (type char) via a pointer to type Fffff which
> is invalid.
>
>   


If this is the case, I agree with the warning, but why is it placed in 
function 'bbb', and not in 'ggg'? 'ggg' is the one that converts from 
unsigned char to Fffff.
I believe this is a bug that message is misplaced. This makes message 
misleading and confusing.
Message line should be fixed, and also it should be one message, not two.

This case should be reopened.

Thank you,
Yuri


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=41368