I am studying a Makefile where the author specified the execution of GCC as follows: gcc -O9 -fno-strict-aliasing ... I could not find any reference to either -O9 or -fno-strict-aliasing in the 4.2.0 gcc.pdf manual. I did find -fstrict-aliasing, but most commands that have a -fno- option are listed in the manual. What effect does -O9 have? Would -fno-strict-aliasing turn off strict-aliasing? Is there a gcc switch that would issue warnings about either obsolete or ignored command line switches? Are there other undocumented switches? Lee.
