On Mon, Feb 25, 2013 at 4:51 AM, Richard Biener <richard.guent...@gmail.com> wrote: > 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. > >> >> 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 and Jason.
Don't worry about possible confusion (-Og needs -gN). Document it at http://gcc.gnu.org/onlinedocs/gcc/Debugging-Options.html#Debugging-Options, and folks should be able to find it. (That's the first place I looked). Address Sanitizer looks very interesting also (-fsanitize=address). It's listed at http://gcc.gnu.org/onlinedocs/gcc/Option-Summary.html, but there's no topic when following the link to http://gcc.gnu.org/onlinedocs/gcc/Debugging-Options.html#Debugging-Options. Jeff
