1 files changed, 70 insertions, 0 deletions
diff --git a/test/std/input.output/iostream.format/output.streams/ostream.seeks/seekp2.pass.cpp b/test/std/input.output/iostream.format/output.streams/ostream.seeks/seekp2.pass.cpp
new file mode 100644
index 0000000000000..ebfd24af91d5b
--- /dev/null
+++ b/test/std/input.output/iostream.format/output.streams/ostream.seeks/seekp2.pass.cpp
@@ -0,0 +1,70 @@
+//===----------------------------------------------------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is dual licensed under the MIT and the University of Illinois Open
+// Source Licenses. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+
+// <ostream>
+
+// template <class charT, class traits = char_traits<charT> >
+//   class basic_ostream;
+
+// basic_ostream<charT,traits>& seekp(off_type off, ios_base::seekdir dir);
+
+#include <ostream>
+#include <cassert>
+
+int seekoff_called = 0;
+
+template <class CharT>
+struct testbuf
+    : public std::basic_streambuf<CharT>
+{
+    typedef std::basic_streambuf<CharT> base;
+    testbuf() {}
+
+protected:
+
+    typename base::pos_type
+    seekoff(typename base::off_type off, std::ios_base::seekdir way,
+                                         std::ios_base::openmode which)
+    {
+        ++seekoff_called;
+        assert(way == std::ios_base::beg);
+        assert(which == std::ios_base::out);
+        return off;
+    }
+};
+
+int main()
+{
+    {
+        seekoff_called = 0;
+        std::ostream os((std::streambuf*)0);
+        assert(&os.seekp(5, std::ios_base::beg) == &os);
+        assert(seekoff_called == 0);
+    }
+    {
+        seekoff_called = 0;
+        testbuf<char> sb;
+        std::ostream os(&sb);
+        assert(&os.seekp(10, std::ios_base::beg) == &os);
+        assert(seekoff_called == 1);
+        assert(os.good());
+        assert(&os.seekp(-1, std::ios_base::beg) == &os);
+        assert(seekoff_called == 2);
+        assert(os.fail());
+    }
+    { // See https://llvm.org/bugs/show_bug.cgi?id=21361
+        seekoff_called = 0;
+        testbuf<char> sb;
+        std::ostream os(&sb);
+        os.setstate(std::ios_base::eofbit);
+        assert(&os.seekp(10, std::ios_base::beg) == &os);
+        assert(seekoff_called == 1);
+        assert(os.rdstate() == std::ios_base::eofbit);
+    }
+}