[PATCH 2/2] qemu/osdep: handle sysconf(_SC_OPEN_MAX) return value == -1

[Clément Léger]

On some systems (MacOS for instance), sysconf(_SC_OPEN_MAX) can return
-1. In that case we should fallback to using the OPEN_MAX define.
According to "man sysconf", the OPEN_MAX define should be present and
provided by either unistd.h and/or limits.h so include them for that
purpose. For other OSes, just assume a maximum of 1024 files descriptors
as a fallback.

Fixes: 4ec5ebea078e ("qemu/osdep: Move close_all_open_fds() to oslib-posix")
Reported-by: Daniel P. Berrangé <berrange@redhat.com>
Signed-off-by: Clément Léger <cleger@rivosinc.com>
---
 util/oslib-posix.c | 12 ++++++++++++
 1 file changed, 12 insertions(+)

diff --git a/util/oslib-posix.c b/util/oslib-posix.c
index 901dcccd73..abf3aa597d 100644
--- a/util/oslib-posix.c
+++ b/util/oslib-posix.c
@@ -44,6 +44,11 @@
 #include "qemu/thread-context.h"
 #include "qemu/main-loop.h"
 
+#ifdef CONFIG_DARWIN
+#include <limits.h>
+#include <unistd.h>
+#endif
+
 #ifdef CONFIG_LINUX
 #include <sys/syscall.h>
 #endif
@@ -928,6 +933,13 @@ static void qemu_close_all_open_fd_fallback(const int 
*skip, unsigned int nskip,
 void qemu_close_all_open_fd(const int *skip, unsigned int nskip)
 {
     int open_max = sysconf(_SC_OPEN_MAX);
+    if (open_max == -1) {
+#ifdef CONFIG_DARWIN
+        open_max = OPEN_MAX;
+#else
+        open_max = 1024;
+#endif
+    }
 
     assert(skip != NULL || nskip == 0);
 
-- 
2.45.2