2 files changed, 11 insertions, 3 deletions
diff --git a/ChangeLog b/ChangeLog
index 48f2aa108f..587c98ee9d 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,8 @@
+Thu Feb 11 20:43:00 2010  Tanaka Akira  <akr@fsij.org>
+
+	* io.c (rb_io_modenum_mode): return "r" for O_RDONLY|O_APPEND.
+	  [ruby-dev:40379]
+
 Thu Feb 11 09:49:31 2010  Tanaka Akira  <akr@fsij.org>
 
 	* lib/resolv.rb: fix [ruby-core:28144] reported by Hans de Graaff.
diff --git a/io.c b/io.c
index eeb6ec510f..9a6ddc9e5f 100644
--- a/io.c
+++ b/io.c
@@ -2910,13 +2910,16 @@ rb_io_modenum_mode(flags)
 #else
 # define MODE_BINARY(a,b) (a)
 #endif
+    int accmode = flags & O_ACCMODE;
     if (flags & O_APPEND) {
-	if ((flags & O_RDWR) == O_RDWR) {
+	if (accmode == O_WRONLY) {
+            return MODE_BINARY("a", "ab");
+        }
+	if (accmode == O_RDWR) {
 	    return MODE_BINARY("a+", "ab+");
 	}
-	return MODE_BINARY("a", "ab");
     }
-    switch (flags & (O_RDONLY|O_WRONLY|O_RDWR)) {
+    switch (accmode) {
       case O_RDONLY:
 	return MODE_BINARY("r", "rb");
       case O_WRONLY: