[Bug target/63223] [avr] Make jumptables work with -Wl,--section-start,.text=

[amylaar at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=63223

--- Comment #9 from Jorn Wolfgang Rennecke <amylaar at gcc dot gnu.org> ---
(In reply to Georg-Johann Lay from comment #8)
> (In reply to Jorn Wolfgang Rennecke from comment #4)
> > (In reply to Georg-Johann Lay from comment #1)
> > do_global_dtors is supposed to start at the start and increment from there.
> > I see it used to be half-way wrong and half-way correct.
> > (Starting at the start, decrementing for __AVR_HAVE_ELPM__, incrementing
> > otherwise.)
> > However, you now made it all the way use an incorrect order - starting at the
> > end and incrementing from there.
> > Is there a rationale for this?
> 
> The old code was broken as it decremented begainning at the start address. 
> The flaw never came apparent for __dtors_start = __dtors_end or with
> simulators that terminated in exit.
> 
> The new code uses the same traverse direction like __do_global_ctors.
> 
> Is the order of .ctors, .dtors defined in any way?  I.e. how do you express
> that constructor A must run before constructor B in the C program?  Same for
> destructors.

The C++ standard says that destructors have to run in reverse order of
completion
of constructors.
crtstuff.c:__do_global_ctors_aux starts at the first constructor, and
increments from there;
crtstuff.c:__do_global_dtors_aux starts at the last destructor, and decrements
from there.