On Fri, 10 Oct 2025 at 21:11, Joseph Myers wrote: > On Fri, 10 Oct 2025, Matthew Malcomson wrote: > > > Questions for others: > > 1) We'd like to double-check that this sounds like a problem before > trying to > > change it. > > 2) Does this trigger thoughts of anything else to look out for? > > 3) Would the best solution be to add some `--as-needed` push/pop state > > arguments into the link line? > > Yes, I'd expect libstdc++ to be linked (DT_NEEDED) with libatomic only if > it actually has undefined references that libatomic resolves. > > We try quite hard to avoid libstdc++ having any undefined references to libatomic functions. The atomics inside the library are defined in terms of the config/cpu/**/atomicity.h functions, which only operate on int and which are defined using inline assembly (and spinlocks when needed). That's partly because those functions predate libatomic, but partly because it makes libstdc++ self-sufficient.
So until now, users only needed to link to libatomic if their own code used atomics on types that require libatomic calls, but libstdc++.so doesn't do that.
