Jeff King <peff@xxxxxxxx> writes:
> That is, does sysconf actually work on such a system (or does it need a
> similar run-time fallback)? And either way, we should try falling back
> to OPEN_MAX rather than 1 if we have it.
Interesting.
> As far as the warning, I am not sure I see a point. The user does not
> have any useful recourse, and git should continue to operate as normal.
> Having every single git invocation print "by the way, RLIMIT_NOFILE does
> not work on your system" seems like it would get annoying.
Very true. That makes the resulting function look like this:
-------------------------------- 8< ------------------------------
static unsigned int get_max_fd_limit(void)
{
#ifdef RLIMIT_NOFILE
struct rlimit lim;
if (!getrlimit(RLIMIT_NOFILE, &lim))
return lim.rlim_cur;
#endif
#if defined(_SC_OPEN_MAX)
{
long sc_open_max = sysconf(_SC_OPEN_MAX);
if (0 < sc_open_max)
return sc_open_max;
}
#if defined(OPEN_MAX)
return OPEN_MAX;
#else
return 1; /* see the caller ;-) */
#endif
}
-------------------------------- >8 ------------------------------
But the sysconf part makes me wonder; here is what we see in
http://pubs.opengroup.org/onlinepubs/9699919799/functions/sysconf.html
If name is an invalid value, sysconf() shall return -1 and set errno
to indicate the error. If the variable corresponding to name is
described in <limits.h> as a maximum or minimum value and the
variable has no limit, sysconf() shall return -1 without changing
the value of errno. Note that indefinite limits do not imply
infinite limits; see <limits.h>.
For a broken system (like RLIMIT_NOFILE defined for the compiler,
but the actual call returns a bogus error), the compiler may see the
_SC_OPEN_MAX defined, while sysconf() may say "I've never heard of
such a name" and return -1, or the system, whether broken or not,
may want to say "Unlimited" and return -1. The caller takes
anything unreasonable as a positive value capped to 25 or something,
so there isn't a real harm if we returned a bogus value from here,
but I am not sure what the safe default behaviour of this function
should be to help such a broken system while not harming systems
that are functioning correctly.
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