[Bug sanitizer/55617] static constructors are not being instrumented correctly on darwin

["jakub at gcc dot gnu.org" <gcc-bugzilla at gcc dot gnu dot org>]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=55617

--- Comment #13 from Jakub Jelinek <jakub at gcc dot gnu.org> 2013-01-30 14:41:14 UTC ---
(In reply to comment #12)
> This one is a necessary one.
> asan_finish_file inserts __asan_init into the array of constructors (aka
> __mod_init_func section). But for some reason it is inserted at the end of that
> array, while the constructors are being executed from the start of the array at
> program startup. That's why the program crashes (because it's trying to execute
> some instrumented code that accesses the shadow memory, which isn't mapped
> yet), and the real question is how do we put the new constructor first provided
> that the ctor priorities do not work well on Darwin.

Guess if Darwin ignores priority, then the reason for that is that
asan_finish_file which adds the ctor is called very late during compilation
(and has to be, otherwise it e.g. wouldn't know if it is needed at all and what
globals need to be registered).
And the bug is clear, config/darwin* shouldn't ignore the priority.  If the
object format is lame enough and doesn't support priorities, at least the
routines should ensure the right priority ordering within the same compilation
unit (whether by not emitting anything right away and queueing it up for emit
very late, sorted according to the priority, or something else, I don't care).