Question about -O1 level

Question about -O1 level

[Mahmood Naderan]

Hi

I have noticed that my program with -O1 receives segmentation fault while if I manually specify all 45 O1 switches described in [1], the programs runs without problem. The gcc version is 9.3.0. I wonder if -O1 do something more than those switches. 

Any thoughts on that?

[1] https://gcc.gnu.org/onlinedocs/gcc-9.3.0/gcc/Optimize-Options.html


Regards,
Mahmood

Re: Question about -O1 level

[Marc Glisse]

On Fri, 30 Jul 2021, Mahmood Naderan via Gcc-help wrote:

> I have noticed that my program with -O1 receives segmentation fault 
> while if I manually specify all 45 O1 switches described in [1], the 
> programs runs without problem. The gcc version is 9.3.0. I wonder if -O1 
> do something more than those switches.

https://gcc.gnu.org/wiki/FAQ#Is_-O1_.28-O2.2C-O3.2C_-Os_or_-Og.29_equivalent_to_individual_-foptimization_options.3F


-- 
Marc Glisse

Re: Question about -O1 level

[Jonathan Wakely]

On Fri, 30 Jul 2021, 15:37 Marc Glisse, <marc.glisse@inria.fr> wrote:

> On Fri, 30 Jul 2021, Mahmood Naderan via Gcc-help wrote:
>
> > I have noticed that my program with -O1 receives segmentation fault
> > while if I manually specify all 45 O1 switches described in [1], the
> > programs runs without problem. The gcc version is 9.3.0. I wonder if -O1
> > do something more than those switches.
>
>
> https://gcc.gnu.org/wiki/FAQ#Is_-O1_.28-O2.2C-O3.2C_-Os_or_-Og.29_equivalent_to_individual_-foptimization_options.3F



That's why what you tried doesn't work. Instead of trying to disable all
the optimization passes, have you tried building your program with
-fsanitize=undefined instead?



>

Re: Question about -O1 level

[Mahmood Naderan]

Thanks. With -fsanitize I got some more hints to find the problem.




Regards,
Mahmood






On Friday, July 30, 2021, 8:56:28 PM GMT+2, Jonathan Wakely <jwakely.gcc@gmail.com> wrote: 







On Fri, 30 Jul 2021, 15:37 Marc Glisse, <marc.glisse@inria.fr> wrote:
> On Fri, 30 Jul 2021, Mahmood Naderan via Gcc-help wrote:
> 
>> I have noticed that my program with -O1 receives segmentation fault 
>> while if I manually specify all 45 O1 switches described in [1], the 
>> programs runs without problem. The gcc version is 9.3.0. I wonder if -O1 
>> do something more than those switches.
> 
> https://gcc.gnu.org/wiki/FAQ#Is_-O1_.28-O2.2C-O3.2C_-Os_or_-Og.29_equivalent_to_individual_-foptimization_options.3F


That's why what you tried doesn't work. Instead of trying to disable all the optimization passes, have you tried building your program with -fsanitize=undefined instead?


> 
>