On Mon, Feb 25, 2013 at 6:20 AM, Chung-Ju Wu <jasonw...@gmail.com> wrote: > 2013/2/25 Jeffrey Walton <noloa...@gmail.com>: >> Hi All, >> >> I read the relase notes on GCC 4.8 >> (http://gcc.gnu.org/gcc-4.8/changes.html) and -Og caught my eye (the >> bulleted item is below). > [deleted] >> >> What "n" does -Og correspond to for -O and -g (i.e., -O1, -O2; -g2, -g3)?
-Og does not correspond to any other -O plus -g level. -Og does not enable debug info creation either (eh, I _knew_ that was going to be confusing ...). To enable debug information generation you need to use -Og -g. -Og optimizes way less than -O1 but more than -O0 (it for example does inlining of C++ abstraction, constant propagation, full redundancy elimination and dead code elimination). > [deleted] >> Is -Og -g3 a valid combination to get the benefits of -Og with maximum >> symbol support? Is it even needed? Yes, it's valid and it's even needed. >> Jeff >> > > To my understanding, '-Og' selects optimization level 1 > so that you can have fast compilation and a superior debugging experience. As said above this is not exactly true. The __OPTIMIZE__ preprocessor macro will be 1 though. > You still need to use -g (or -g3, which is the option you normally use.) > to guide GCC output debug information. > > Refer to following link for some -Og implementation detail: > http://gcc.gnu.org/ml/gcc-patches/2012-08/msg00616.html Also note that evaluation whether 1), 2) or 3) hold true has not been done, bugreports are welcome. Thanks, Richard. > > Best regards, > jasonwu
