Re: [PATCH] nptl: Move stack list variables into _rtld_global

[Florian Weimer via Gdb-patches <gdb-patches@sourceware.org>]

* Simon Marchi:

>>> If we have to deal with this, I guess that GDB should now do things in a
>>> different order: go through the whole library list and load their
>>> symbols.  And then if one of those libraries were libpthread, try to
>>> initialize libthread_db.
>> 
>> Initialization of libthread_db should be unconditional.  Programs use
>> TLS data without linking against libpthread.  And glibc 2.34 might not
>> have a separate libpthread at all.
>
> Ok, currently GDB attempts to load libthread_db when noticing the main
> objfile / program (I guess it is needed if the program is statically
> linked to libpthread?) or when seeing a library named libpthread*.

Would it be possible to load libthread_db unconditionally after loading
all shared objects?  Then it is loaded only once.

> About the hypothetical scenario for glibc 2.34: do you mean that the
> pthread infrastructure will directly be in libc.so?  If so, our current
> strategy of attempting to load libthread_db only for the main program
> or a libpthread* library will indeed not work.  And I suppose that will
> also require trying to load libthread_db on every new shared lib...

I think one attempt loading is enough, after all shared objects are
available.  In both the attaching and starting case, libpthread will be
seen by libthread_db if it is there.  I do not think it is necessary to
try loading libpthread_db again for each dlopen.  Maybe you could
restrict that to trigger on libpthread, but then dlopen of libpthread
does not really work today.

Thanks,
Florian