--- a/lib/ChangeLog
+++ b/lib/ChangeLog
@@ -1,3 +1,8 @@
+2005-07-26  Bruno Haible  <bruno@clisp.org>
+
+	* lock.h: Update from GNU gettext.
+	* lock.c: Update from GNU gettext.
+
 2005-07-18  Bruno Haible  <bruno@clisp.org>
 
 	* lock.h (gl_once_t): New type.

--- a/lib/lock.c
+++ b/lib/lock.c
@@ -32,6 +32,43 @@
 
 /* Use the POSIX threads library.  */
 
+# if PTHREAD_IN_USE_DETECTION_HARD
+
+/* The function to be executed by a dummy thread.  */
+static void *
+dummy_thread_func (void *arg)
+{
+  return arg;
+}
+
+int
+glthread_in_use (void)
+{
+  static int tested;
+  static int result; /* 1: linked with -lpthread, 0: only with libc */
+
+  if (!tested)
+    {
+      pthread_t thread;
+
+      if (pthread_create (&thread, NULL, dummy_thread_func, NULL) != 0)
+	/* Thread creation failed.  */
+	result = 0;
+      else
+	{
+	  /* Thread creation works.  */
+	  void *retval;
+	  if (pthread_join (thread, &retval) != 0)
+	    abort ();
+	  result = 1;
+	}
+      tested = 1;
+    }
+  return result;
+}
+
+# endif
+
 /* -------------------------- gl_lock_t datatype -------------------------- */
 
 /* ------------------------- gl_rwlock_t datatype ------------------------- */

--- a/lib/lock.h
+++ b/lib/lock.h
@@ -68,6 +68,15 @@
 # include <pthread.h>
 # include <stdlib.h>
 
+# if PTHREAD_IN_USE_DETECTION_HARD
+
+/* The pthread_in_use() detection needs to be done at runtime.  */
+#  define pthread_in_use() \
+     glthread_in_use ()
+extern int glthread_in_use (void);
+
+# endif
+
 # if USE_POSIX_THREADS_WEAK
 
 /* Use weak references to the POSIX threads library.  */
@@ -109,12 +118,16 @@
 #   pragma weak pthread_self
 #  endif
 
-#  pragma weak pthread_cancel
-#  define pthread_in_use() (pthread_cancel != NULL)
+#  if !PTHREAD_IN_USE_DETECTION_HARD
+#   pragma weak pthread_cancel
+#   define pthread_in_use() (pthread_cancel != NULL)
+#  endif
 
 # else
 
-#  define pthread_in_use() 1
+#  if !PTHREAD_IN_USE_DETECTION_HARD
+#   define pthread_in_use() 1
+#  endif
 
 # endif
 

--- a/m4/ChangeLog
+++ b/m4/ChangeLog
@@ -1,3 +1,7 @@
+2005-07-26  Bruno Haible  <bruno@clisp.org>
+
+	* lock.m4: Update from GNU gettext.
+
 2005-07-25  Paul Eggert  <eggert@cs.ucla.edu>
 
 	* regex.m4 (gl_INCLUDED_REGEX): Use AC_RUN_ELSE instead of the

--- a/m4/lock.m4
+++ b/m4/lock.m4
@@ -16,9 +16,17 @@
 dnl programs that really need multithread functionality. The difference
 dnl between LIBTHREAD and LIBMULTITHREAD is that on platforms supporting weak
 dnl symbols, typically LIBTHREAD="" whereas LIBMULTITHREAD="-lpthread".
+dnl Adds to CPPFLAGS the flag -D_REENTRANT or -D_THREAD_SAFE if needed for
+dnl multithread-safe programs.
 
 AC_DEFUN([gl_LOCK],
 [
+  dnl Ordering constraints: This macro modifies CPPFLAGS in a way that
+  dnl influences the result of the autoconf tests that test for *_unlocked
+  dnl declarations, on AIX 5 at least. Therefore it must come early.
+  AC_BEFORE([$0], [gl_FUNC_GLIBC_UNLOCKED_IO])dnl
+  AC_BEFORE([$0], [gl_ARGP])dnl
+
   AC_REQUIRE([AC_CANONICAL_HOST])
   AC_REQUIRE([AC_GNU_SOURCE]) dnl needed for pthread_rwlock_t on glibc systems
   dnl Check for multithreading.
@@ -51,19 +59,22 @@
         #   -lgthreads
         case "$host_os" in
           osf*)
-            # On OSF/1, the compiler needs the flag -pthread so that it groks
-            # <pthread.h>. For the linker, it is equivalent to -lpthread.
-            if test -n "$GCC"; then
-              # gcc-2.95 doesn't understand -pthread, only -D_REENTRANT.
-              CPPFLAGS="$CPPFLAGS -D_REENTRANT"
-            else
-              CPPFLAGS="$CPPFLAGS -pthread"
-            fi
+            # On OSF/1, the compiler needs the flag -D_REENTRANT so that it
+            # groks <pthread.h>. cc also understands the flag -pthread, but
+            # we don't use it because 1. gcc-2.95 doesn't understand -pthread,
+            # 2. putting a flag into CPPFLAGS that has an effect on the linker
+            # causes the AC_TRY_LINK test below to succeed unexpectedly,
+            # leading to wrong values of LIBTHREAD and LTLIBTHREAD.
+            CPPFLAGS="$CPPFLAGS -D_REENTRANT"
             ;;
         esac
         gl_have_pthread=
+        # Test whether both pthread_mutex_lock and pthread_mutexattr_init exist
+        # in libc. IRIX 6.5 has the first one in both libc and libpthread, but
+        # the second one only in libpthread, and lock.c needs it.
         AC_TRY_LINK([#include <pthread.h>],
-          [pthread_mutex_lock((pthread_mutex_t*)0);],
+          [pthread_mutex_lock((pthread_mutex_t*)0);
+           pthread_mutexattr_init((pthread_mutexattr_t*)0);],
           [gl_have_pthread=yes])
         # Test for libpthread by looking for pthread_kill. (Not pthread_self,
         # since it is defined as a macro on OSF/1.)
@@ -71,7 +82,17 @@
           # The program links fine without libpthread. But it may actually
           # need to link with libpthread in order to create multiple threads.
           AC_CHECK_LIB(pthread, pthread_kill,
-            [LIBMULTITHREAD=-lpthread LTLIBMULTITHREAD=-lpthread])
+            [LIBMULTITHREAD=-lpthread LTLIBMULTITHREAD=-lpthread
+             # On Solaris and HP-UX, most pthread functions exist also in libc.
+             # Therefore pthread_in_use() needs to actually try to create a
+             # thread: pthread_create from libc will fail, whereas
+             # pthread_create will actually create a thread.
+             case "$host_os" in
+               solaris* | hpux*)
+                 AC_DEFINE([PTHREAD_IN_USE_DETECTION_HARD], 1,
+                   [Define if the pthread_in_use() detection is hard.])
+             esac
+            ])
         else
           # Some library is needed. Try libpthread and libc_r.
           AC_CHECK_LIB(pthread, pthread_kill,
@@ -115,7 +136,8 @@
             [AC_DEFINE([HAVE_PTHREAD_MUTEX_RECURSIVE], 1,
                [Define if the <pthread.h> defines PTHREAD_MUTEX_RECURSIVE.])])
           # Some systems optimize for single-threaded programs by default, and
-          # need special flags to disable these optimizations.
+          # need special flags to disable these optimizations. For example, the
+          # definition of 'errno' in <errno.h>.
           case "$host_os" in
             aix* | freebsd*) CPPFLAGS="$CPPFLAGS -D_THREAD_SAFE" ;;
             solaris*) CPPFLAGS="$CPPFLAGS -D_REENTRANT" ;;
@@ -235,7 +257,8 @@
 dnl Solaris 7,8,9     posix       -lpthread       Y      Sol 7,8: 0.0; Sol 9: OK
 dnl                   solaris     -lthread        Y      Sol 7,8: 0.0; Sol 9: OK
 dnl
-dnl HP-UX 11          posix       -lpthread       Y      OK
+dnl HP-UX 11          posix       -lpthread       N (cc) OK
+dnl                                               Y (gcc)
 dnl
 dnl IRIX 6.5          posix       -lpthread       Y      0.5
 dnl