* Leon Timmermans: > On Mon, Jun 2, 2025 at 10:22 AM Florian Weimer via perl5-porters > <perl5-port...@perl.org> wrote: >> >> * Stig Palmquist: >> >> > References >> > ---------- >> > https://github.com/Perl/perl5/commit/918bfff86ca8d6d4e4ec5b30994451e0bd74aba9.patch >> >> Is this fix really correct? >> >> + ret = fdopendir(dup(my_dirfd(dp))); >> >> This does not create a separate open file description, only a second >> descriptor that shares the read position of the directory stream with >> the original directory stream. I think you have to use something like >> this: >> >> ret = fdopendir(openat(my_dirfd(dp), ".", O_DIRECTORY | O_CLOEXEC)); > > Our thread cloning in general is a terribly awkward business, where > "what is the correct behavior" isn't always well defined or possible; > I can see the arguments for both to be honest. > > For file descriptors we don't create new file descriptions either (we > don't even create new file descriptors, we refcount them), so why > should we do so for directory handles? I'm not sure that expectation > makes sense in that context.
That's a fair point. It's more like fork in this regard, which has similar failure cases for DIR * objects (shared file description, but unshared buffers and a separate descriptor). > And if we did go the openat way, I don't think that seekdir on the new > handle with the telldir of the old one is necessarily valid if the > directory has been changed (I mean even a rewinddir can invalidate > telldir's return value). I don't think we can do a fully correct copy > here. Ugh, I had not considered that. Yes, glibc will have to switch to an implementation where telldir offsets are specific to a DIR * for certain file systems on 32-bit architectures (because telldir returns long, not off_t). Hopefully sharing the description isn't much of a problem in practice. Thanks, Florian
