[PATCH] io.c: reopen stdio streams correctly when given "w+"

[Eric Wong <e@80x24.org>]

* io.c (rb_io_oflags_modestr): handle O_TRUNC correctly
* test/ruby/test_io.rb (test_reopen_stdio): new test

Patch-by: cremno phobia <cremno@mail.ru>

[ruby-core:69779] [Bug #11319]
---
 io.c                 | 3 +++
 test/ruby/test_io.rb | 9 +++++++++
 2 files changed, 12 insertions(+)

diff --git a/io.c b/io.c
index 8844987..6c62c97 100644
--- a/io.c
+++ b/io.c
@@ -5033,6 +5033,9 @@ rb_io_oflags_modestr(int oflags)
       case O_WRONLY:
 	return MODE_BINARY("w", "wb");
       case O_RDWR:
+	if (oflags & O_TRUNC) {
+	    return MODE_BINARY("w+", "wb+");
+	}
 	return MODE_BINARY("r+", "rb+");
     }
 }
diff --git a/test/ruby/test_io.rb b/test/ruby/test_io.rb
index 9b3e801..9ded25b 100644
--- a/test/ruby/test_io.rb
+++ b/test/ruby/test_io.rb
@@ -2069,6 +2069,15 @@ End
     }
   end
 
+  def test_reopen_stdio
+    mkcdtmpdir {
+      fname = 'bug11319'
+      File.write(fname, 'hello')
+      system(EnvUtil.rubybin, '-e', "STDOUT.reopen('#{fname}', 'w+')")
+      assert_equal('', File.read(fname))
+    }
+  end
+
   def test_reopen_mode
     feature7067 = '[ruby-core:47694]'
     make_tempfile {|t|
-- 
EW