1 /* Return the internal lock used by mbrtowc and mbrtoc32.
2 Copyright (C) 2019-2020 Free Software Foundation, Inc.
3
4 This program is free software: you can redistribute it and/or modify
5 it under the terms of the GNU General Public License as published by
6 the Free Software Foundation; either version 3 of the License, or
7 (at your option) any later version.
8
9 This program is distributed in the hope that it will be useful,
10 but WITHOUT ANY WARRANTY; without even the implied warranty of
11 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
12 GNU General Public License for more details.
13
14 You should have received a copy of the GNU General Public License
15 along with this program. If not, see <https://www.gnu.org/licenses/>. */
16
17 /* Written by Bruno Haible <bruno@clisp.org>, 2019-2020. */
18
19 #include <config.h>
20
21 /* When it is known that the gl_get_mbtowc_lock function is defined
22 by a dependency library, it should not be defined here. */
23 #if OMIT_MBTOWC_LOCK
24
25 /* This declaration is solely to ensure that after preprocessing
26 this file is never empty. */
27 typedef int dummy;
28
29 #else
30
31 /* This file defines the internal lock used by mbrtowc and mbrtoc32.
32 It is a separate compilation unit, so that only one copy of it is
33 present when linking statically. */
34
35 /* Prohibit renaming this symbol. */
36 # undef gl_get_mbtowc_lock
37
38 /* Macro for exporting a symbol (function, not variable) defined in this file,
39 when compiled into a shared library. */
40 # ifndef DLL_EXPORTED
41 # if HAVE_VISIBILITY
42 /* Override the effect of the compiler option '-fvisibility=hidden'. */
43 # define DLL_EXPORTED __attribute__((__visibility__("default")))
44 # elif defined _WIN32 || defined __CYGWIN__
45 # define DLL_EXPORTED __declspec(dllexport)
46 # else
47 # define DLL_EXPORTED
48 # endif
49 # endif
50
51 # if defined _WIN32 && !defined __CYGWIN__
52
53 # define WIN32_LEAN_AND_MEAN /* avoid including junk */
54 # include <windows.h>
55
56 # include "windows-initguard.h"
57
58 /* The return type is a 'CRITICAL_SECTION *', not a 'glwthread_mutex_t *',
59 because the latter is not guaranteed to be a stable ABI in the future. */
60
61 /* Make sure the function gets exported from DLLs. */
62 DLL_EXPORTED CRITICAL_SECTION *gl_get_mbtowc_lock (void);
63
64 static glwthread_initguard_t guard = GLWTHREAD_INITGUARD_INIT;
65 static CRITICAL_SECTION lock;
66
67 /* Returns the internal lock used by mbrtowc and mbrtoc32. */
68 CRITICAL_SECTION *
gl_get_mbtowc_lock(void)69 gl_get_mbtowc_lock (void)
70 {
71 if (!guard.done)
72 {
73 if (InterlockedIncrement (&guard.started) == 0)
74 {
75 /* This thread is the first one to need the lock. Initialize it. */
76 InitializeCriticalSection (&lock);
77 guard.done = 1;
78 }
79 else
80 {
81 /* Don't let guard.started grow and wrap around. */
82 InterlockedDecrement (&guard.started);
83 /* Yield the CPU while waiting for another thread to finish
84 initializing this mutex. */
85 while (!guard.done)
86 Sleep (0);
87 }
88 }
89 return &lock;
90 }
91
92 # elif HAVE_PTHREAD_API
93
94 # include <pthread.h>
95
96 static pthread_mutex_t mutex = PTHREAD_MUTEX_INITIALIZER;
97
98 /* Make sure the function gets exported from shared libraries. */
99 DLL_EXPORTED pthread_mutex_t *gl_get_mbtowc_lock (void);
100
101 /* Returns the internal lock used by mbrtowc and mbrtoc32. */
102 pthread_mutex_t *
gl_get_mbtowc_lock(void)103 gl_get_mbtowc_lock (void)
104 {
105 return &mutex;
106 }
107
108 # elif HAVE_THREADS_H
109
110 # include <threads.h>
111 # include <stdlib.h>
112
113 static int volatile init_needed = 1;
114 static once_flag init_once = ONCE_FLAG_INIT;
115 static mtx_t mutex;
116
117 static void
atomic_init(void)118 atomic_init (void)
119 {
120 if (mtx_init (&mutex, mtx_plain) != thrd_success)
121 abort ();
122 init_needed = 0;
123 }
124
125 /* Make sure the function gets exported from shared libraries. */
126 DLL_EXPORTED mtx_t *gl_get_mbtowc_lock (void);
127
128 /* Returns the internal lock used by mbrtowc and mbrtoc32. */
129 mtx_t *
gl_get_mbtowc_lock(void)130 gl_get_mbtowc_lock (void)
131 {
132 if (init_needed)
133 call_once (&init_once, atomic_init);
134 return &mutex;
135 }
136
137 # endif
138
139 # if (defined _WIN32 || defined __CYGWIN__) && !defined _MSC_VER
140 /* Make sure the '__declspec(dllimport)' in mbrtowc.c and mbrtoc32.c does not
141 cause a link failure when no DLLs are involved. */
142 # if defined _WIN64 || defined _LP64
143 # define IMP(x) __imp_##x
144 # else
145 # define IMP(x) _imp__##x
146 # endif
147 void * IMP(gl_get_mbtowc_lock) = &gl_get_mbtowc_lock;
148 # endif
149
150 #endif
151