------- Additional Comments From fastsnip-bcard1 at yahoo dot com 2005-05-01 20:30 ------- Subject: Re: O2 and O3 memory access error - compiled program - incorrect debug output
On Sunday 01 May 2005 16:25, you wrote: > ------- Additional Comments From fastsnip-bcard1 at yahoo dot com > 2005-05-01 20:24 ------- Subject: Re: O2 and O3 memory access error - > compiled program - incorrect debug output > > On Sunday 01 May 2005 15:40, you wrote: > > ------- 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. > > Okay I tried the following optimizing options: > > -O1 -funit-at-a-time ==== program ran fine > -O1 ==== program ran fine > -O2 -funit-at-a-time ==== memory access error > -O3 -funit-at-a-time ==== memory access error > > It seems that O2 and O3 only trigger the memory access error. > > > Do not know exactly what you mean by "Also make sure that you are not > invoking undefined behavior." Exactly how do I do this. Is there something > in 4.0.0 that wasn't in 2.95 through 3.4.3 that would trigger this? The > program compiled and ran fine under previous versions with the same > compilation optimization options. > > > 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. Yes these warnings are fine to have and check - unfortunately the compiler cannot run through the code logic and I find that these warnings are generated spuriously because of that. Once you cycle through the code logic, the warning is unfounded. Again, good as a check, but it can generatea lot of un-necessary warnings and create a LOT of work checking logic. Thanks, Terry -- http://gcc.gnu.org/bugzilla/show_bug.cgi?id=21322
