Hello, On Wed, 24 Aug 2022, Florian Weimer wrote:
> > Isn't this merely moving the failure point from exception-at-ctor to > > dlopen-fails? > > Yes, and that is a soft error that can be handled (likewise for > pthread_create). Makes sense. Though that actually hints at a design problem with ELF static ctors/dtors: they should be able to soft-fail (leading to dlopen or pthread_create error returns). So, maybe the _best_ way to deal with this is to extend the definition of the various object-initionalization means in ELF to allow propagating failure. > > Probably a note section, which the link editor could either transform into > > a dynamic tag or leave as note(s) in the PT_NOTE segment. The latter > > wouldn't require any specific tooling support in the link editor. But the > > consumer would have to iterate through all the notes to add the > > individual counts together. Might be acceptable, though. > > I think we need some level of link editor support to avoid drastically > over-counting multiple static calls that get merged into one > implementation as the result of vague linkage. Not sure how to express > that at the ELF level? Hmm. The __cxa_atexit calls are coming from the per-file local static initialization_and_destruction routine which doesn't have vague linkage, so its contribution to the overall number of cxa_atexit calls doesn't change from .o to final-exe. Can you show an example of what you're worried about? A completely different way would be to not use cxa_atexit at all: allocate memory statically for the object and dtor addresses in .rodata (instead of in .text right now), and iterate over those at static_destruction time. (For the thread-local ones it would need to store arguments to __tls_get_addr). Doing that or defining failure modes for ELF init/fini seems a better design than hacking around the current limitation via counting static cxa_atexit calls. Ciao, Michael.
