include/boost/corosio/native/detail/iocp/win_wsa_init.hpp

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win_wsa_init.hpp
f(x) Functions (6)
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1 //
2 // Copyright (c) 2025 Vinnie Falco ([email protected])
3 // Copyright (c) 2026 Steve Gerbino
4 //
5 // Distributed under the Boost Software License, Version 1.0. (See accompanying
6 // file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
7 //
8 // Official repository: https://github.com/cppalliance/corosio
9 //
10
11 #ifndef BOOST_COROSIO_NATIVE_DETAIL_IOCP_WIN_WSA_INIT_HPP
12 #define BOOST_COROSIO_NATIVE_DETAIL_IOCP_WIN_WSA_INIT_HPP
13
14 #include <boost/corosio/detail/platform.hpp>
15
16 #if BOOST_COROSIO_HAS_IOCP
17
18 #include <boost/corosio/detail/config.hpp>
19 #include <boost/corosio/native/detail/make_err.hpp>
20 #include <boost/corosio/detail/except.hpp>
21
22 #include <boost/corosio/native/detail/iocp/win_windows.hpp>
23
24 namespace boost::corosio::detail {
25
26 /** RAII class for Winsock initialization.
27
28 Uses reference counting to ensure WSAStartup is called once on
29 first construction and WSACleanup on last destruction.
30
31 Derive from this class to ensure Winsock is initialized before
32 any socket operations.
33 */
34 class BOOST_COROSIO_DECL win_wsa_init
35 {
36 protected:
37 win_wsa_init();
38 ~win_wsa_init();
39
40 win_wsa_init(win_wsa_init const&) = delete;
41 win_wsa_init& operator=(win_wsa_init const&) = delete;
42 };
43
44 // Process-wide Winsock init refcount. Kept as an inline function-local
45 // static (one shared instance across TUs) rather than a static data member
46 // so win_wsa_init can carry BOOST_COROSIO_DECL: an exported/imported static
47 // data member defined in a header is rejected by MSVC and clang-cl
48 // ("definition of dllimport static field not allowed").
49 inline long&
50 13208x win_wsa_init_count() noexcept
51 {
52 static long count = 0;
53 13208x return count;
54 }
55
56 // Hold Winsock for the life of the process, so the count never falls back
57 // to zero between one io_context and the next. An asynchronous
58 // GetAddrInfoExW keeps settling inside ws2_32 past its completion
59 // routine, with no way to observe when, and a WSACleanup under it faults
60 // on a system DNS thread.
61 inline void
62 6507x win_wsa_hold_process() noexcept
63 {
64 struct holder
65 {
66 80x holder() noexcept
67 {
68 80x ::InterlockedIncrement(&win_wsa_init_count());
69 80x }
70
71 80x ~holder()
72 {
73
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160x if (::InterlockedDecrement(&win_wsa_init_count()) == 0)
74 80x ::WSACleanup();
75 80x }
76 };
77
78
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6507x static holder const instance;
79 6507x }
80
81 6524x inline win_wsa_init::win_wsa_init()
82 {
83
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13048x if (::InterlockedIncrement(&win_wsa_init_count()) == 1)
84 {
85 WSADATA wsaData;
86
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97x int result = ::WSAStartup(MAKEWORD(2, 2), &wsaData);
87
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97x if (result != 0)
88 {
89 17x ::InterlockedDecrement(&win_wsa_init_count());
90 17x throw_system_error(make_err(result));
91 }
92 }
93
94 // After the startup above, which must own the first count.
95 6507x win_wsa_hold_process();
96 6507x }
97
98 6507x inline win_wsa_init::~win_wsa_init()
99 {
100
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13014x if (::InterlockedDecrement(&win_wsa_init_count()) == 0)
101 ::WSACleanup();
102 6507x }
103
104 } // namespace boost::corosio::detail
105
106 #endif // BOOST_COROSIO_HAS_IOCP
107
108 #endif // BOOST_COROSIO_NATIVE_DETAIL_IOCP_WIN_WSA_INIT_HPP
109