1 //===----------------------------------------------------------------------===//
2 //
3 //                     The LLVM Compiler Infrastructure
4 //
5 // This file is dual licensed under the MIT and the University of Illinois Open
6 // Source Licenses. See LICENSE.TXT for details.
7 //
8 //===----------------------------------------------------------------------===//
9 
10 // <ostream>
11 
12 // template <class charT, class traits = char_traits<charT> >
13 //   class basic_ostream;
14 
15 // basic_ostream<charT,traits>& seekp(pos_type pos);
16 
17 #include <ostream>
18 #include <cassert>
19 
20 int seekpos_called = 0;
21 
22 template <class CharT>
23 struct testbuf
24     : public std::basic_streambuf<CharT>
25 {
26     typedef std::basic_streambuf<CharT> base;
testbuftestbuf27     testbuf() {}
28 
29 protected:
30 
31     typename base::pos_type
seekpostestbuf32     seekpos(typename base::pos_type sp, std::ios_base::openmode which)
33     {
34         ++seekpos_called;
35         assert(which == std::ios_base::out);
36         return sp;
37     }
38 };
39 
main()40 int main()
41 {
42     {
43         seekpos_called = 0;
44         std::ostream os((std::streambuf*)0);
45         assert(&os.seekp(5) == &os);
46         assert(seekpos_called == 0);
47     }
48     {
49         seekpos_called = 0;
50         testbuf<char> sb;
51         std::ostream os(&sb);
52         assert(&os.seekp(10) == &os);
53         assert(seekpos_called == 1);
54         assert(os.good());
55         assert(&os.seekp(-1) == &os);
56         assert(seekpos_called == 2);
57         assert(os.fail());
58     }
59     { // See https://llvm.org/bugs/show_bug.cgi?id=21361
60         seekpos_called = 0;
61         testbuf<char> sb;
62         std::ostream os(&sb);
63         os.setstate(std::ios_base::eofbit);
64         assert(&os.seekp(10) == &os);
65         assert(seekpos_called == 1);
66         assert(os.rdstate() == std::ios_base::eofbit);
67     }
68 }
69