[Bug c/66373] New: gcc downloaded from Fedora 21 repository produces defective executable. Same source code with gcc from Fedora 19 and Fedora 20 works fine

[Bug c/66373] New: gcc downloaded from Fedora 21 repository produces defective executable. Same source code with gcc from Fedora 19 and Fedora 20 works fine

[juanslayton at dslextreme dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=66373

            Bug ID: 66373
           Summary: gcc downloaded from Fedora 21 repository produces
                    defective executable.  Same source code with gcc from
                    Fedora 19 and Fedora 20 works fine
           Product: gcc
           Version: unknown
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c
          Assignee: unassigned at gcc dot gnu.org
          Reporter: juanslayton at dslextreme dot com
  Target Milestone: ---

Created attachment 35675
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=35675&action=edit
source code and 3 compilations from different gcc versions

In the attached files, xs.c is the source file for a program that polls 40 USB
keyboards (the “student keyboards”) and does various things with any input that
it finds.  Files a, b, and c are executable files produced by 3 different
editions of gcc downloaded from Fedora repositories.  Each was compiled with
“gcc -Wall -Wextra -lSDL2 -lrt -lSDL2_ttf -O3 xs.c”.  Each compilation was
clean, with no errors or warnings.

Files a and b work beautifully.  File c misbehaves in such a way as to render
the program unusable.  Under the circumstances, suspicion falls on the latest
edition of gcc as downloaded from the Fedora 21 repository.

Here are the specifics.

File a was compiled with Fedora 19, gcc version 4.8.2 20131212 (Red Hat
4.8.2-7)

File b was compiled with Fedora 20, gcc version 4.8.3 20140911 (Red Hat
4.8.3-7)

File c was compiled with Fedora 21, gcc version 4.9.2 20150212 (Red Hat
4.9.2-6)

The failure seems to be on a return from subroutine get_event, lines  2919ff,
of xp.c  This subroutine is called to read keystrokes from student boards and
return them to the calling routines.  There are 7 such routines; four present
math facts drills, one gives keyboarding practice, one gives advice on written
work from a textbook, and one is a rudimentary word processor.  They process
returns from get_event in various ways, but the run time error is the same for
each of them, which points to get_event as the error location.  This is not a
sure thing, and it could be that whatever the error is, it could be duplicated
in each of the 7 calling routines.  

The error is this, when get_event returns 10, (ie, ‘enter’ has been pushed) the
program jumps to the primary program menu, rather than continuing the routine
that called get_event.  Whether it does this by going through that routine, or
by somehow going around it, I haven’t yet determined.  But the fact that only
compilations under the latest gcc edition show this behavior,  suggests a bug
in the compiler.  I can’t imagine what it would be.
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From: "juanslayton at dslextreme dot com" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug c/66373] gcc downloaded from Fedora 21 repository produces defective executable.  Same source code with gcc from Fedora 19 and Fedora 20 works fine
Date: Tue, 02 Jun 2015 04:48:00 -0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?idf373

--- Comment #1 from John Slayton <juanslayton at dslextreme dot com> ---
reference to xp.c should be xs.c

[Bug c/66373] gcc downloaded from Fedora 21 repository produces defective executable. Same source code with gcc from Fedora 19 and Fedora 20 works fine

[pinskia at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=66373

--- Comment #2 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
Can you provide the preprocessed source?  As I don't have SDL2 installed here. 
Also really since you are compiling with redhat's gcc, you should report it to
them.

[Bug c/66373] gcc downloaded from Fedora 21 repository produces defective executable. Same source code with gcc from Fedora 19 and Fedora 20 works fine

[juanslayton at dslextreme dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=66373

--- Comment #3 from John Slayton <juanslayton at dslextreme dot com> ---
Yeah, this will probably have to go to redhat.  But I'll give you what I
can.  xstar.tar is the installation package for the whole program.
Dependencies are SDL2, SDL2-devel, SDL2_ttf, SDL2_ttf-devel, and freetype.
"preprocessed" was produced by gcc 4.9.2-6 (the version that fails).  I can
work up a preprocessed file from the other 2 versions if it would be of any
use.  Would take me a while, though, as it involves swapping out the hard
drives that have those versions.
js

On Mon, Jun 1, 2015 at 10:07 PM, pinskia at gcc dot gnu.org <
gcc-bugzilla@gcc.gnu.org> wrote:

> https://gcc.gnu.org/bugzilla/show_bug.cgi?id=66373
>
> --- Comment #2 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
> Can you provide the preprocessed source?  As I don't have SDL2 installed
> here.
> Also really since you are compiling with redhat's gcc, you should report
> it to
> them.
>
> --
> You are receiving this mail because:
> You reported the bug.
>

[Bug c/66373] gcc downloaded from Fedora 21 repository produces defective executable. Same source code with gcc from Fedora 19 and Fedora 20 works fine

[jakub at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=66373

--- Comment #4 from Jakub Jelinek <jakub at gcc dot gnu.org> ---
You should try valgrind on the program, compile/link with
-fsanitize=address,undefined and see what it reports during runtime, try
different compiler options.
If you then still suspect a compiler bug, please try to turn your program into
a self-contained reproducer, see http://gcc.gnu.org/bugs/ for details.

[Bug c/66373] gcc downloaded from Fedora 21 repository produces defective executable. Same source code with gcc from Fedora 19 and Fedora 20 works fine

[mpolacek at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=66373

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |WAITING
   Last reconfirmed|                            |2015-06-22
                 CC|                            |mpolacek at gcc dot gnu.org
     Ever confirmed|0                           |1

[Bug c/66373] gcc downloaded from Fedora 21 repository produces defective executable. Same source code with gcc from Fedora 19 and Fedora 20 works fine

[juanslayton at dslextreme dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=66373

--- Comment #5 from John Slayton <juanslayton at dslextreme dot com> ---
valgrind revealed many memory leaks.  I plugged most of them and the new
source code compiles and runs well on Red Hat 4.9.2-6.

Conclusion:  no bug in gcc version.

thanks for your time.
John Slayton

On Mon, Jun 22, 2015 at 11:04 AM, mpolacek at gcc dot gnu.org <
gcc-bugzilla@gcc.gnu.org> wrote:

> https://gcc.gnu.org/bugzilla/show_bug.cgi?id=66373
>
> Marek Polacek <mpolacek at gcc dot gnu.org> changed:
>
>            What    |Removed                     |Added
>
> ----------------------------------------------------------------------------
>              Status|UNCONFIRMED                 |WAITING
>    Last reconfirmed|                            |2015-06-22
>                  CC|                            |mpolacek at gcc dot
> gnu.org
>      Ever confirmed|0                           |1
>
> --
> You are receiving this mail because:
> You reported the bug.
>

[Bug c/66373] gcc downloaded from Fedora 21 repository produces defective executable. Same source code with gcc from Fedora 19 and Fedora 20 works fine

[pinskia at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=66373

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

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

--- Comment #6 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
Closing as invalid then.