http://gcc.gnu.org/bugzilla/show_bug.cgi?id=49576
--- Comment #4 from Olaf van der Spek <olafvdspek at gmail dot com> 2011-06-29 18:12:24 UTC --- Suppose your app has 10557 include directives. What do you add to your PCH? Why /usr/include? Because these headers are unlikely to change, so they're a good candidate for PCH.
