From a3a4f4d061ed4fc1debbee0fe172a786c7c152d5 Mon Sep 17 00:00:00 2001
From: ksss <co000ri@gmail.com>
Date: Sat, 27 May 2017 13:29:38 +0900
Subject: IO#sysread Check for readable

---
 src/io.c | 3 +++
 1 file changed, 3 insertions(+)

(limited to 'src')

diff --git a/src/io.c b/src/io.c
index 6d1b39cc5..e0de0ca36 100644
--- a/src/io.c
+++ b/src/io.c
@@ -637,6 +637,9 @@ mrb_io_sysread(mrb_state *mrb, mrb_value io)
   }
 
   fptr = (struct mrb_io *)io_get_open_fptr(mrb, io);
+  if (!fptr->readable) {
+    mrb_raise(mrb, E_IO_ERROR, "not opened for reading");
+  }
   ret = read(fptr->fd, RSTRING_PTR(buf), maxlen);
   switch (ret) {
     case 0: /* EOF */
-- 
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