On 03/06/16 09:18, Chris Vine wrote: > POSIX allows only async-signal-safe functions (see signal(7)) to be > called in the child between fork() and exec(), which drastically limits > the usefulness of child setup functions
There's a gap here between the theory (GLib mostly has only POSIX requirements) and the practice (glibc malloc is designed to allow things POSIX doesn't, and this useful functionality would be difficult to achieve without that). In principle GLib could call opendir() on /proc/$pid before forking, then read it in the child, but readdir() isn't async-signal-safe either. Doing the reading in the parent isn't a solution, because the parent is potentially multi-threaded, so it could be opening and closing file descriptors in other threads (racing with the readdir()). In principle the parent could read the new child's fd table and write a list of fds into a pipe, for the child to close them all or set them all close-on-exec, while the child waits for EOF on that pipe before proceeding with the close and exec operations... but that seems fairly horrible. I think what we really want here is *BSD closefrom(), which at least FreeBSD documents as async-signal-safe. Unfortunately, Linux doesn't have that system call. libdbus would have the same issue on platforms that don't have closefrom(). -- Simon McVittie Collabora Ltd. <http://www.collabora.com/> _______________________________________________ gtk-devel-list mailing list gtk-devel-list@gnome.org https://mail.gnome.org/mailman/listinfo/gtk-devel-list
