On Apr 10 11:03, Jeremy Drake via Cygwin wrote: > On Thu, 10 Apr 2025, Corinna Vinschen via Cygwin wrote: > > > > It seems glibc takes care of this implicit deregistration in > > > __cxa_finalize, after calling __cxa_atexit functions, it unregisters any > > > at_quick_exit or pthread_atfork callbacks from the DSO being unloaded. > > > > > > https://sourceware.org/git/?p=glibc.git;a=blob;f=stdlib/cxa_finalize.c;h=2bb35602edc6bf842e5d2c93ad03454d7b57ee65;hb=HEAD > > > > > > It doesn't look like newlib deals with either at_quick_exit or > > > pthread_atfork handlers in its __cxa_finalize implementation. > > > > Cygwin is doing this stuff mostly in its own code, see thread.cc. > > It keeps lists of the callbacks in a global structure which is > > called MT_INTERFACE throughout thread.cc. > > > > The functions pthread::atforkprepare(), pthread::atforkparent() and > > pthread::atforkchild () are called from different spots during fork(). > > > > Here's what we're missing: > > > > - Either keep track of the DLL a callback function is coming from by > > calling dlls.find (handle, true) and store the struct dll pointer. > > In dlclose(), if the DLL is of type DLL_LOAD or DLL_NATIVE, and > > the refcounter indicates that this is the last FreeLibrary, check the > > three callback lists in MT_INTERFACE and remove all functions > > with the same struct dll pointer. > > I'm inclined to take this approach.
You can do the cleanup in dll_list::detach, btw. > What about at_quick_exit though? > That's entirely within newlib, isn't it? Yes, and it's neither DSO aware, nor is it called during a normal exit. I'd ignore it for now, or we need a new implementation along the lines of the GLibc implementation which always stores the DSO handle together with the handler function. But that's something for 3.7, not a bugfix for 3.6. Corinna > > -- > Problem reports: https://cygwin.com/problems.html > FAQ: https://cygwin.com/faq/ > Documentation: https://cygwin.com/docs.html > Unsubscribe info: https://cygwin.com/ml/#unsubscribe-simple -- Problem reports: https://cygwin.com/problems.html FAQ: https://cygwin.com/faq/ Documentation: https://cygwin.com/docs.html Unsubscribe info: https://cygwin.com/ml/#unsubscribe-simple
