Messages in this thread |  | | Subject | Re: [PATCH] nextfd(2) | From | Colin Walters <> | Date | Wed, 04 Apr 2012 13:10:12 -0400 |
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On Wed, 2012-04-04 at 09:31 -0700, KOSAKI Motohiro wrote:
> Ideally possible. but practically impossible. 2) people don't use a their > own malloc. they only uses open sources alternative malloc. And, I think > you have too narrowing concern. Even though malloc people adds a workaround, > the standard inhibit to use it
What do you mean? If as hpa says, the maintainer of e.g. google tcmalloc added a call to pthread_atfork(), then code which uses opendir() would start working.
> and people may continue to use more dangerous > RLIM_NOFILE loop. 1) I haven't seen _practical_ userland software uses such > linux internal hacking. Almost all major software can run on multiple OSs.
Except that if you're using /proc/self/fd, you're already relying on Linux-specific functionality. So it's not burdensome to use "struct linux_dirent" and O_DIRECTORY either.
In GLib we're presently doing the regular /proc+opendir() under #ifdef __linux__: http://git.gnome.org/browse/glib/tree/glib/gspawn.c#n932
Now I'd happily switch to hpa's fdwalk() implementation if I was aware of someone using glib in combination with an alternative malloc hitting this problem.
Basically I think hpa is right here, and it's not really worth adding a new system call.
The thing is, even if it were added today, since we need to run on old kernels, we'd have to carry the code to use the /proc trick approximately forever. And in the end all nextfd() would accomplish would be a *third* case in the already messy ifdefs/fallbacks in the various implementations of process spawning.
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