[Bug c/60350] New: Incorrect -Wmaybe-uninitialized warning with incorrect location information

[Bug c/60350] New: Incorrect -Wmaybe-uninitialized warning with incorrect location information

[chengniansun at gmail dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=60350

            Bug ID: 60350
           Summary: Incorrect -Wmaybe-uninitialized warning with incorrect
                    location information
           Product: gcc
           Version: 4.9.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c
          Assignee: unassigned at gcc dot gnu.org
          Reporter: chengniansun at gmail dot com

Two questions regarding the following case
1) the variables "pf" and "pv" are uninitialized, but not maybe-uninitialized.
I am not sure whether this is the design choice of gcc. 

2) The column numbers of the two warnings point to the same location ":", which
is not right. 


$: cat s.c 
void a(int i) {
  int (*pf)[2];
  int (*pv)[i + 1];
  (i ? pf : pv);
}
$: gcc-trunk -Wuninitialized -c s.c 
s.c: In function ‘a’:
s.c:4:11: warning: ‘pf’ may be used uninitialized in this function
[-Wmaybe-uninitialized]
   (i ? pf : pv);
           ^
s.c:4:11: warning: ‘pv’ may be used uninitialized in this function
[-Wmaybe-uninitialized]
$: gcc-trunk --version
gcc-trunk (GCC) 4.9.0 20140226 (experimental)
Copyright (C) 2014 Free Software Foundation, Inc.
This is free software; see the source for copying conditions.  There is NO
warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
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Subject: [Bug fortran/60341] ICE compiling Nonmem 6.2.0
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http://gcc.gnu.org/bugzilla/show_bug.cgi?id`341

--- Comment #7 from Steve Kargl <sgk at troutmask dot apl.washington.edu> ---
On Wed, Feb 26, 2014 at 08:38:57PM +0000, mikael at gcc dot gnu.org wrote:
>
> Looks like an unguarded union access.
> This is a regression from the time there was now front-end optimization I
> guess?

Unfortunately, I've deleted versions of gfortran older than
4.6.x.  The code fails with all version above 4.6.x.  If
one adds -fno-frontend-optimize, then the code compiles.
So, yes, it is a regression.

[Bug c/60350] Incorrect -Wmaybe-uninitialized warning with incorrect location information

[pinskia at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=60350

Andrew Pinski <pinskia at gcc dot gnu.org> changed:

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

--- Comment #1 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
>2) The column numbers of the two warnings point to the same location ":", which is not right. 

This is most likely due to the casting which is added by the triany operator.

[Bug middle-end/60350] Incorrect -Wmaybe-uninitialized warning with incorrect location information

[mpolacek at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=60350

Marek Polacek <mpolacek at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |NEW
   Last reconfirmed|                            |2014-02-27
                 CC|                            |mpolacek at gcc dot gnu.org
          Component|c                           |middle-end
     Ever confirmed|0                           |1

--- Comment #2 from Marek Polacek <mpolacek at gcc dot gnu.org> ---
I think the maybe-used-uninitialized warning is in place here, it depends on I
whether pf or pv is evaluated.  The column info looks bogus indeed.

[Bug middle-end/60350] Incorrect -Wmaybe-uninitialized warning with incorrect location information

[chengniansun at gmail dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=60350

--- Comment #3 from Chengnian Sun <chengniansun at gmail dot com> ---
(In reply to Marek Polacek from comment #2)
> I think the maybe-used-uninitialized warning is in place here, it depends on
> I whether pf or pv is evaluated.  The column info looks bogus indeed.

Thanks, Marek. I misunderstood the meaning of maybe-used-uninitialized warnings