git_open_cloexec(): use fcntl(2) w/ FD_CLOEXEC fallback

A platform might not support open(2) with O_CLOEXEC but may support
telling the same with fcntl(2) to flip FD_CLOEXEC bit on on an open
file descriptor.  It is a fallback that is inherently racy and this
may not be worth doing, though.

Suggested-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

diff --git a/sha1_file.c b/sha1_file.c
index dfbf398183d5b9593b56c27b8cf5011d0ddd5e84..64e1a21fc61ed24a0b33c12578eab50546ec6270 100644 (file)
--- a/sha1_file.c
+++ b/sha1_file.c
@@ -1561,14 +1561,28 @@ int check_sha1_signature(const unsigned char *sha1, void *map,
 
 int git_open_cloexec(const char *name, int flags)
 {
-       static int cloexec = O_CLOEXEC;
-       int fd = open(name, flags | cloexec);
+       int fd;
+       static int o_cloexec = O_CLOEXEC;
 
-       if ((cloexec & O_CLOEXEC) && fd < 0 && errno == EINVAL) {
+       fd = open(name, flags | o_cloexec);
+       if ((o_cloexec & O_CLOEXEC) && fd < 0 && errno == EINVAL) {
                /* Try again w/o O_CLOEXEC: the kernel might not support it */
-               cloexec &= ~O_CLOEXEC;
-               fd = open(name, flags | cloexec);
+               o_cloexec &= ~O_CLOEXEC;
+               fd = open(name, flags | o_cloexec);
        }
+
+#if defined(F_GETFL) && defined(F_SETFL) && defined(FD_CLOEXEC)
+       {
+               static int fd_cloexec = FD_CLOEXEC;
+
+               if (!o_cloexec && 0 <= fd && fd_cloexec) {
+                       /* Opened w/o O_CLOEXEC?  try with fcntl(2) to add it */
+                       int flags = fcntl(fd, F_GETFL);
+                       if (fcntl(fd, F_SETFL, flags | fd_cloexec))
+                               fd_cloexec = 0;
+               }
+       }
+#endif
        return fd;
 }