Спецификации такие спецификации

http://pubs.opengroup.org/onlinepubs/9699919799/utilities/c99.html

-O optlevel

Specify the level of code optimization. If the optlevel option-argument is the digit '0' , all special code optimizations shall be disabled. If it is the digit '1' , the nature of the optimization is unspecified. If the -O option is omitted, the nature of the system's default optimization is unspecified. It is unspecified whether code generated in the presence of the -O 0 option is the same as that generated when -O is omitted. Other optlevel values may be supported.

P. S. А когда Остин очень-очень хочет, но никак не может, получается

http://pubs.opengroup.org/onlinepubs/9699919799/utilities/logger.html