[Bug c/21322] O2 and O3 memory access error - compiled program - incorrect debug output

["pinskia at gcc dot gnu dot org" <gcc-bugzilla at gcc dot gnu dot org>]

------- Additional Comments From pinskia at gcc dot gnu dot org  2005-05-01 19:40 -------
(In reply to comment #5)
> Subject: Re:  O2 and O3 memory access error - compiled program - incorrect debug output
> 
> On Sunday 01 May 2005 15:19, you wrote:
> > ------- Additional Comments From pinskia at gcc dot gnu dot org  2005-05-01
> > 19:19 ------- Also can you look to see you have any warnings with -W -Wall?
> > The warnings about unsigned vs signed were there before just enabled with
> > -pedantic.
> >
> > Also does -fno-strict-aliasing help if so this might not be a bug in GCC
> > but your code.
> 
> Compiled with the above flag as you suggested - no change - I still get a 
> memory access error using "-O3" optiomization.
> 
> Will try the "-W -Wall" flags top see what that produces and let you know.
> 
> Terry

Hmm, try -O1 -funit-at-a-time also make sure that you are not going past an array bounds.
Also make sure that you are not invoking undefined behavior.

I get a lot of warnings about uninitialized variables like so:
awkpcmp.c: In function 'c_pop':
awkpcmp.c:57: warning: 'R_Token' may be used uninitialized in this function
awkpcmp.c: In function 'c_primary_expr':
awkpcmp.c:159: warning: 'arg2' may be used uninitialized in this function
awkpcmp.c:158: warning: 'arg1' may be used uninitialized in this function
awkpcmp.c: In function 'c_statement':
awkpcmp.c:1122: warning: 'Last_Token' may be used uninitialized in this function
awkpcmp.c: In function 'set_user_fun':
awkpcmp.c:1789: warning: 'name' may be used uninitialized in this function

so you might just be invoking undefined.

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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=21322