From fdf39963490cf2cf95b30d91bb9b35964c2c2350 Mon Sep 17 00:00:00 2001
From: Nobuyoshi Nakada <nobu@ruby-lang.org>
Date: Wed, 22 Dec 2021 15:33:12 +0900
Subject: Empty and return the buffer if zero size is given [Bug #18421]

In `IO#readpartial` and `IO#read_nonblock`, as well as `IO#read`.
---
 test/ruby/test_io.rb | 21 +++++++++++++++++++++
 1 file changed, 21 insertions(+)

(limited to 'test/ruby')

diff --git a/test/ruby/test_io.rb b/test/ruby/test_io.rb
index b46777df5f..4f54052d3b 100644
--- a/test/ruby/test_io.rb
+++ b/test/ruby/test_io.rb
@@ -1494,6 +1494,13 @@ class TestIO < Test::Unit::TestCase
     end)
   end
 
+  def test_readpartial_zero_size
+    File.open(IO::NULL) do |r|
+      assert_empty(r.readpartial(0, s = "01234567"))
+      assert_empty(s)
+    end
+  end
+
   def test_readpartial_buffer_error
     with_pipe do |r, w|
       s = ""
@@ -1539,6 +1546,13 @@ class TestIO < Test::Unit::TestCase
     end)
   end
 
+  def test_read_zero_size
+    File.open(IO::NULL) do |r|
+      assert_empty(r.read(0, s = "01234567"))
+      assert_empty(s)
+    end
+  end
+
   def test_read_buffer_error
     with_pipe do |r, w|
       s = ""
@@ -1576,6 +1590,13 @@ class TestIO < Test::Unit::TestCase
     }
   end
 
+  def test_read_nonblock_zero_size
+    File.open(IO::NULL) do |r|
+      assert_empty(r.read_nonblock(0, s = "01234567"))
+      assert_empty(s)
+    end
+  end
+
   def test_write_nonblock_simple_no_exceptions
     pipe(proc do |w|
       w.write_nonblock('1', exception: false)
-- 
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