1  /* Return the internal lock used by mbrtowc and mbrtoc32.
       2     Copyright (C) 2019-2023 Free Software Foundation, Inc.
       3  
       4     This file is free software: you can redistribute it and/or modify
       5     it under the terms of the GNU Lesser General Public License as
       6     published by the Free Software Foundation; either version 2.1 of the
       7     License, or (at your option) any later version.
       8  
       9     This file 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 Lesser General Public License for more details.
      13  
      14     You should have received a copy of the GNU Lesser 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 *
      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 *
     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
     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 *
     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