mbrtowc: Ensure the mbtowc_lock is unique.

* lib/mbtowc-lock.c: New file, based on lib/setlocale-lock.c.
* lib/mbtowc-lock.h: New file, extracted from lib/mbrtowc.c and
lib/setlocale_null.c.
* lib/mbrtowc.c: Include headers needed for mbtowc-lock.h. Don't include
glthread/lock.h. Include mbtowc-lock.h.
(mbtowc_lock): Remove declaration.
(mbrtowc): Use mbtowc_with_lock.
* m4/mbrtowc.m4 (gl_FUNC_MBRTOWC): Require gl_PTHREADLIB. Check for
threads.h. Set LIB_MBRTOWC.
(gl_PREREQ_MBTOWC_LOCK): New macro.
* modules/mbrtowc (Files): Add lib/mbtowc-lock.h, lib/mbtowc-lock.c,
lib/windows-initguard.h, m4/threadlib.m4, m4/visibility.m4.
(Depends-on): Remove lock.
(configure.ac): Arrange to compile mbtowc-lock.c.
(Link): Mention $(LIB_MBRTOWC) instead of $(LIBTHREAD).
* modules/acl (Link): Likewise.
* modules/argmatch (Link): Likewise.
* modules/backup-rename (Link): Likewise.
* modules/backupfile (Link): Likewise.
* modules/closein (Link): Likewise.
* modules/closeout (Link): Likewise.
* modules/copy-file (Link): Likewise.
* modules/csharpcomp (Link): Likewise.
* modules/csharpexec (Link): Likewise.
* modules/dfa (Link): Likewise.
* modules/exclude (Link): Likewise.
* modules/fnmatch (Link): Likewise.
* modules/fnmatch-gnu (Link): Likewise.
* modules/fnmatch-posix (Link): Likewise.
* modules/glob (Link): Likewise.
* modules/human (Link): Likewise.
* modules/javacomp (Link): Likewise.
* modules/javaexec (Link): Likewise.
* modules/javaversion (Link): Likewise.
* modules/mbfile (Link): Likewise.
* modules/mbiter (Link): Likewise.
* modules/mbmemcasecmp (Link): Likewise.
* modules/mbmemcasecoll (Link): Likewise.
* modules/mbrlen (Link): Likewise.
* modules/mbscasecmp (Link): Likewise.
* modules/mbscasestr (Link): Likewise.
* modules/mbschr (Link): Likewise.
* modules/mbscspn (Link): Likewise.
* modules/mbsinit (Link): Likewise.
* modules/mbslen (Link): Likewise.
* modules/mbsncasecmp (Link): Likewise.
* modules/mbsnlen (Link): Likewise.
* modules/mbsnrtowcs (Link): Likewise.
* modules/mbspbrk (Link): Likewise.
* modules/mbspcasecmp (Link): Likewise.
* modules/mbsrchr (Link): Likewise.
* modules/mbsrtowcs (Link): Likewise.
* modules/mbssep (Link): Likewise.
* modules/mbsspn (Link): Likewise.
* modules/mbsstr (Link): Likewise.
* modules/mbstok_r (Link): Likewise.
* modules/mbswidth (Link): Likewise.
* modules/mbuiter (Link): Likewise.
* modules/mkdir-p (Link): Likewise.
* modules/propername (Link): Likewise.
* modules/quote (Link): Likewise.
* modules/quotearg (Link): Likewise.
* modules/quotearg-simple (Link): Likewise.
* modules/regex-quote (Link): Likewise.
* modules/rpmatch (Link): Likewise.
* modules/sh-quote (Link): Likewise.
* modules/system-quote (Link): Likewise.
* modules/trim (Link): Likewise.
* modules/unistdio/ulc-asnprintf (Link): Likewise.
* modules/unistdio/ulc-fprintf (Link): Likewise.
* modules/unistdio/ulc-vasnprintf (Link): Likewise.
* modules/unistdio/ulc-vasprintf (Link): Likewise.
* modules/unistdio/ulc-vfprintf (Link): Likewise.
* modules/unistdio/ulc-vsnprintf (Link): Likewise.
* modules/unistdio/ulc-vsprintf (Link): Likewise.
* modules/xfreopen (Link): Likewise.
* modules/xmemcoll (Link): Likewise.
* modules/yesno (Link): Likewise.
* modules/regex (Link): Add $(LIB_MBRTOWC).
* modules/acl-tests (Makefile.am): Link the programs with $(LIB_MBRTOWC)
instead of $(LIBTHREAD).
* modules/argmatch-tests (Makefile.am): Likewise.
* modules/closein-tests (Makefile.am): Likewise.
* modules/copy-file-tests (Makefile.am): Likewise.
* modules/dfa-tests (Makefile.am): Likewise.
* modules/fnmatch-tests (Makefile.am): Likewise.
* modules/glob-tests (Makefile.am): Likewise.
* modules/mbmemcasecmp-tests (Makefile.am): Likewise.
* modules/mbmemcasecoll-tests (Makefile.am): Likewise.
* modules/mbrtowc-tests (Makefile.am): Likewise.
* modules/mbscasecmp-tests (Makefile.am): Likewise.
* modules/mbscasestr-tests (Makefile.am): Likewise.
* modules/mbschr-tests (Makefile.am): Likewise.
* modules/mbscspn-tests (Makefile.am): Likewise.
* modules/mbsinit-tests (Makefile.am): Likewise.
* modules/mbsncasecmp-tests (Makefile.am): Likewise.
* modules/mbsnrtowcs-tests (Makefile.am): Likewise.
* modules/mbspbrk-tests (Makefile.am): Likewise.
* modules/mbspcasecmp-tests (Makefile.am): Likewise.
* modules/mbsrchr-tests (Makefile.am): Likewise.
* modules/mbsrtowcs-tests (Makefile.am): Likewise.
* modules/mbsspn-tests (Makefile.am): Likewise.
* modules/mbsstr-tests (Makefile.am): Likewise.
* modules/quotearg-simple-tests (Makefile.am): Likewise.
* modules/quotearg-tests (Makefile.am): Likewise.
* modules/readtokens-tests (Makefile.am): Likewise.
* modules/sh-quote-tests (Makefile.am): Likewise.
* modules/system-quote-tests (Makefile.am): Likewise.
* modules/unistdio/ulc-asnprintf-tests (Makefile.am): Likewise.
* modules/unistdio/ulc-vasnprintf-tests (Makefile.am): Likewise.
* modules/unistdio/ulc-vasprintf-tests (Makefile.am): Likewise.
* modules/unistdio/ulc-vsnprintf-tests (Makefile.am): Likewise.
* modules/unistdio/ulc-vsprintf-tests (Makefile.am): Likewise.
* modules/yesno-tests (Makefile.am): Likewise.
* modules/exclude-tests (Makefile.am): Link the programs with
$(LIB_MBRTOWC).
* modules/regex-tests (Makefile.am): Likewise.
* modules/regex-quote-tests (Makefile.am): Likewise.

1 files changed, 150 insertions, 0 deletions

diff --git a/lib/mbtowc-lock.c b/lib/mbtowc-lock.c
new file mode 100644
index 0000000000..85ad3c4c90
--- /dev/null
+++ b/lib/mbtowc-lock.c
@@ -0,0 +1,150 @@
+/* Return the internal lock used by mbrtowc and mbrtoc32.
+   Copyright (C) 2019-2020 Free Software Foundation, Inc.
+
+   This program is free software: you can redistribute it and/or modify
+   it under the terms of the GNU General Public License as published by
+   the Free Software Foundation; either version 3 of the License, or
+   (at your option) any later version.
+
+   This program is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+   GNU General Public License for more details.
+
+   You should have received a copy of the GNU General Public License
+   along with this program.  If not, see <https://www.gnu.org/licenses/>.  */
+
+/* Written by Bruno Haible <bruno@clisp.org>, 2019-2020.  */
+
+#include <config.h>
+
+/* When it is known that the gl_get_mbtowc_lock function is defined
+   by a dependency library, it should not be defined here.  */
+#if OMIT_MBTOWC_LOCK
+
+/* This declaration is solely to ensure that after preprocessing
+   this file is never empty.  */
+typedef int dummy;
+
+#else
+
+/* This file defines the internal lock used by mbrtowc and mbrtoc32.
+   It is a separate compilation unit, so that only one copy of it is
+   present when linking statically.  */
+
+/* Prohibit renaming this symbol.  */
+# undef gl_get_mbtowc_lock
+
+/* Macro for exporting a symbol (function, not variable) defined in this file,
+   when compiled into a shared library.  */
+# ifndef DLL_EXPORTED
+#  if HAVE_VISIBILITY
+  /* Override the effect of the compiler option '-fvisibility=hidden'.  */
+#   define DLL_EXPORTED __attribute__((__visibility__("default")))
+#  elif defined _WIN32 || defined __CYGWIN__
+#   define DLL_EXPORTED __declspec(dllexport)
+#  else
+#   define DLL_EXPORTED
+#  endif
+# endif
+
+# if defined _WIN32 && !defined __CYGWIN__
+
+#  define WIN32_LEAN_AND_MEAN  /* avoid including junk */
+#  include <windows.h>
+
+#  include "windows-initguard.h"
+
+/* The return type is a 'CRITICAL_SECTION *', not a 'glwthread_mutex_t *',
+   because the latter is not guaranteed to be a stable ABI in the future.  */
+
+/* Make sure the function gets exported from DLLs.  */
+DLL_EXPORTED CRITICAL_SECTION *gl_get_mbtowc_lock (void);
+
+static glwthread_initguard_t guard = GLWTHREAD_INITGUARD_INIT;
+static CRITICAL_SECTION lock;
+
+/* Returns the internal lock used by mbrtowc and mbrtoc32.  */
+CRITICAL_SECTION *
+gl_get_mbtowc_lock (void)
+{
+  if (!guard.done)
+    {
+      if (InterlockedIncrement (&guard.started) == 0)
+        {
+          /* This thread is the first one to need the lock.  Initialize it.  */
+          InitializeCriticalSection (&lock);
+          guard.done = 1;
+        }
+      else
+        {
+          /* Don't let guard.started grow and wrap around.  */
+          InterlockedDecrement (&guard.started);
+          /* Yield the CPU while waiting for another thread to finish
+             initializing this mutex.  */
+          while (!guard.done)
+            Sleep (0);
+        }
+    }
+  return &lock;
+}
+
+# elif HAVE_PTHREAD_API
+
+#  include <pthread.h>
+
+static pthread_mutex_t mutex = PTHREAD_MUTEX_INITIALIZER;
+
+/* Make sure the function gets exported from shared libraries.  */
+DLL_EXPORTED pthread_mutex_t *gl_get_mbtowc_lock (void);
+
+/* Returns the internal lock used by mbrtowc and mbrtoc32.  */
+pthread_mutex_t *
+gl_get_mbtowc_lock (void)
+{
+  return &mutex;
+}
+
+# elif HAVE_THREADS_H
+
+#  include <threads.h>
+#  include <stdlib.h>
+
+static int volatile init_needed = 1;
+static once_flag init_once = ONCE_FLAG_INIT;
+static mtx_t mutex;
+
+static void
+atomic_init (void)
+{
+  if (mtx_init (&mutex, mtx_plain) != thrd_success)
+    abort ();
+  init_needed = 0;
+}
+
+/* Make sure the function gets exported from shared libraries.  */
+DLL_EXPORTED mtx_t *gl_get_mbtowc_lock (void);
+
+/* Returns the internal lock used by mbrtowc and mbrtoc32.  */
+mtx_t *
+gl_get_mbtowc_lock (void)
+{
+  if (init_needed)
+    call_once (&init_once, atomic_init);
+  return &mutex;
+}
+
+# endif
+
+# if (defined _WIN32 || defined __CYGWIN__) && !defined _MSC_VER
+/* Make sure the '__declspec(dllimport)' in mbrtowc.c and mbrtoc32.c does not
+   cause a link failure when no DLLs are involved.  */
+#  if defined _WIN64 || defined _LP64
+#   define IMP(x) __imp_##x
+#  else
+#   define IMP(x) _imp__##x
+#  endif
+void * IMP(gl_get_mbtowc_lock) = &gl_get_mbtowc_lock;
+# endif
+
+#endif