On Sun, Sep 10, 2017 at 12:37:06PM +0200, René Scharfe wrote: > > And in fact, being called from a signal handler means we should > > generally avoid touching malloc or free (which could be holding locks). > > That would mean preferring a leak to strbuf_release(). Of course that is > > the tip of the iceberg. We call strbuf_addstr() here, and > > remove_dir_recursively() will grow our buffer. > > And we call opendir(3), readdir(3), and closedir(3), which are also not > listed as async-safe functions by POSIX [1]. Good point. I don't know how dangerous those are in the real-world (i.e., is POSIX leaving an out for some implementations, or are they really unsafe on common platforms like Linux). > > So I actually wonder if junk_git_dir and junk_work_tree should be > > pre-sized strbufs themselves. And that makes the leak "go away" in the > > eyes of leak-checkers because we hold onto the static strbufs until > > program exit. > > We could start with a small buffer and expand it to match the path > length of written files as we go. Yes, but I didn't want to touch each code site that creates a file, which is a lot more invasive. I expect expanding to 4096 (or PATH_MAX) would be sufficient in practice. I'd also note that the current code isn't _remotely_ async safe and nobody's complained. So I'm perfectly happy doing nothing, too. I care a bit more about the tempfile.c interface because it's invoked a lot more frequently. > Deletion without readdir(3) requires us to keep a list of all written > files and directories, though. Perhaps in the form of an append-only > log; the signal handler could then go through them in reverse order > and remove them. Or is there a better way? No, I think that's how you'd have to do it. The implementation isn't all that bad, but hitting every file-creation would be invasive. I'd almost rather bail to exec-ing "rm -rf $dir", but we probably can't do _that_ in a signal-handler either. :) -Peff
