normal	2018-11-28 10:10:40 +0900 (Wed, 28 Nov 2018)

  New Revision: 66060

  https://svn.ruby-lang.org/cgi-bin/viewvc.cgi?view=revision&revision=66060

  Log:
    io.c (rb_update_max_fd): use F_GETFL if possible
    
    On 64-bit Linux, fstat() needs to fill out a 144 byte struct
    while F_GETFL only needs to return 8 bytes.
    
    Fwiw, F_GETFD requires an additional rcu_read_lock and bitmap
    check; so it's obviously more expensive than F_GETFL on Linux.
    
    Reduce stack usage of rb_update_max_fd from 184 to 24 bytes.

  Modified files:
    trunk/io.c
Index: io.c
===================================================================
--- io.c	(revision 66059)
+++ io.c	(revision 66060)
@@ -193,14 +193,22 @@ static rb_atomic_t max_file_descriptor = https://github.com/ruby/ruby/blob/trunk/io.c#L193
 void
 rb_update_max_fd(int fd)
 {
-    struct stat buf;
     rb_atomic_t afd = (rb_atomic_t)fd;
     rb_atomic_t max_fd = max_file_descriptor;
+    int err;
 
     if (afd <= max_fd)
         return;
 
-    if (fstat(fd, &buf) != 0 && errno == EBADF) {
+#if defined(HAVE_FCNTL) && defined(F_GETFL)
+    err = fcntl(fd, F_GETFL) == -1;
+#else
+    {
+        struct stat buf;
+        err = fstat(fd, &buf) != 0;
+    }
+#endif
+    if (err && errno == EBADF) {
         rb_bug("rb_update_max_fd: invalid fd (%d) given.", fd);
     }
 

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