Question about -O1 level

[Mahmood Naderan via Gcc-help <gcc-help@xxxxxxxxxxx>]

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