[PATCH v2] ntdll: Use the true maximum open FDs to set the limit on Mac.

[Chip Davis]

The actual upper limit is stored in the sysctl(3)
"kern.maxfilesperproc". This value may be higher than the value of the
OPEN_MAX constant.

Using sysconf(3) with _SC_OPEN_MAX just returns the current value of
RLIMIT_NOFILE, so that won't work here.

Signed-off-by: Chip Davis <cdavis5x at gmail.com>
---
v2: Remove unnecessary #ifdefs.
---
 dlls/ntdll/unix/loader.c | 22 ++++++++++++++++------
 1 file changed, 16 insertions(+), 6 deletions(-)

diff --git a/dlls/ntdll/unix/loader.c b/dlls/ntdll/unix/loader.c
index d5867e4aa754..0617fca631c1 100644
--- a/dlls/ntdll/unix/loader.c
+++ b/dlls/ntdll/unix/loader.c
@@ -452,13 +452,23 @@ static void set_max_limit( int limit )
         rlimit.rlim_cur = rlimit.rlim_max;
         if (setrlimit( limit, &rlimit ) != 0)
         {
-#if defined(__APPLE__) && defined(RLIMIT_NOFILE) && defined(OPEN_MAX)
-            /* On Leopard, setrlimit(RLIMIT_NOFILE, ...) fails on attempts to set
-             * rlim_cur above OPEN_MAX (even if rlim_max > OPEN_MAX). */
-            if (limit == RLIMIT_NOFILE && rlimit.rlim_cur > OPEN_MAX)
+#if defined(__APPLE__) && defined(RLIMIT_NOFILE)
+            if (limit == RLIMIT_NOFILE)
             {
-                rlimit.rlim_cur = OPEN_MAX;
-                setrlimit( limit, &rlimit );
+                /* On Leopard, setrlimit(RLIMIT_NOFILE, ...) fails on attempts to set
+                 * rlim_cur above OPEN_MAX (even if rlim_max > OPEN_MAX). */
+                int open_max;
+                /* This is the true OPEN_MAX; it may be greater than the constant.
+                 * sysconf(_SC_OPEN_MAX) won't work here: it just returns getrlimit(RLIMIT_NOFILE). */
+                static int maxfilesperproc_oid[] = { CTL_KERN, KERN_MAXFILESPERPROC };
+                size_t len = sizeof(open_max);
+                if (sysctl( maxfilesperproc_oid, ARRAY_SIZE(maxfilesperproc_oid), &open_max, &len, NULL, 0 ) != 0)
+                    open_max = OPEN_MAX;
+                if (rlimit.rlim_cur > open_max)
+                {
+                    rlimit.rlim_cur = open_max;
+                    setrlimit( limit, &rlimit );
+                }
             }
 #endif
         }
-- 
2.34.1