Index: gcc/fortran/trans-decl.c
===================================================================
--- gcc/fortran/trans-decl.c	(Revision 259739)
+++ gcc/fortran/trans-decl.c	(Arbeitskopie)
@@ -699,7 +699,8 @@ gfc_finish_var_decl (tree decl, gfc_symbol * sym)
 	      && CLASS_DATA (sym)->ts.u.derived->attr.has_dtio_procs)))
     TREE_STATIC (decl) = 1;
 
-  if (sym->attr.volatile_)
+  /* Treat asynchronous variables the same as volatile, for now.  */
+  if (sym->attr.volatile_ || sym->attr.asynchronous)
     {
       TREE_THIS_VOLATILE (decl) = 1;
       TREE_SIDE_EFFECTS (decl) = 1;
Index: gcc/fortran/trans-io.c
===================================================================
--- gcc/fortran/trans-io.c	(Revision 259739)
+++ gcc/fortran/trans-io.c	(Arbeitskopie)
@@ -438,10 +438,9 @@ gfc_build_io_library_fndecls (void)
 	get_identifier (PREFIX("st_iolength")), ".w",
 	void_type_node, 1, dt_parm_type);
 
-  /* TODO: Change when asynchronous I/O is implemented.  */
   parm_type = build_pointer_type (st_parameter[IOPARM_ptype_wait].type);
   iocall[IOCALL_WAIT] = gfc_build_library_function_decl_with_spec (
-	get_identifier (PREFIX("st_wait")), ".X",
+	get_identifier (PREFIX("st_wait_async")), ".w",
 	void_type_node, 1, parm_type);
 
   parm_type = build_pointer_type (st_parameter[IOPARM_ptype_filepos].type);
@@ -1527,7 +1526,7 @@ gfc_trans_wait (gfc_code * code)
     mask |= IOPARM_common_err;
 
   if (p->id)
-    mask |= set_parameter_value (&block, var, IOPARM_wait_id, p->id);
+    mask |= set_parameter_ref (&block, &post_block, var, IOPARM_wait_id, p->id);
 
   set_parameter_const (&block, var, IOPARM_common_flags, mask);
 
Index: libgfortran/Makefile.am
===================================================================
--- libgfortran/Makefile.am	(Revision 259739)
+++ libgfortran/Makefile.am	(Arbeitskopie)
@@ -100,7 +100,8 @@ io/transfer128.c \
 io/unit.c \
 io/unix.c \
 io/write.c \
-io/fbuf.c
+io/fbuf.c \
+io/async.c
 
 endif
 
@@ -108,7 +109,8 @@ gfor_io_headers= \
 io/io.h \
 io/fbuf.h \
 io/format.h \
-io/unix.h
+io/unix.h \
+io/async.h
 
 gfor_helper_src= \
 intrinsics/associated.c \
Index: libgfortran/Makefile.in
===================================================================
--- libgfortran/Makefile.in	(Revision 259739)
+++ libgfortran/Makefile.in	(Arbeitskopie)
@@ -70,7 +70,8 @@ target_triplet = @target@
 @LIBGFOR_MINIMAL_FALSE@io/unit.c \
 @LIBGFOR_MINIMAL_FALSE@io/unix.c \
 @LIBGFOR_MINIMAL_FALSE@io/write.c \
-@LIBGFOR_MINIMAL_FALSE@io/fbuf.c
+@LIBGFOR_MINIMAL_FALSE@io/fbuf.c \
+@LIBGFOR_MINIMAL_FALSE@io/async.c
 
 @LIBGFOR_MINIMAL_FALSE@am__append_3 = \
 @LIBGFOR_MINIMAL_FALSE@intrinsics/access.c \
@@ -352,7 +353,7 @@ am__objects_47 = $(am__objects_4) $(am__objects_5)
 @LIBGFOR_MINIMAL_FALSE@	inquire.lo intrinsics.lo list_read.lo \
 @LIBGFOR_MINIMAL_FALSE@	lock.lo open.lo read.lo transfer.lo \
 @LIBGFOR_MINIMAL_FALSE@	transfer128.lo unit.lo unix.lo write.lo \
-@LIBGFOR_MINIMAL_FALSE@	fbuf.lo
+@LIBGFOR_MINIMAL_FALSE@	fbuf.lo async.lo
 am__objects_49 = size_from_kind.lo $(am__objects_48)
 @LIBGFOR_MINIMAL_FALSE@am__objects_50 = access.lo c99_functions.lo \
 @LIBGFOR_MINIMAL_FALSE@	chdir.lo chmod.lo clock.lo cpu_time.lo \
@@ -650,7 +651,8 @@ gfor_io_headers = \
 io/io.h \
 io/fbuf.h \
 io/format.h \
-io/unix.h
+io/unix.h \
+io/async.h
 
 gfor_helper_src = intrinsics/associated.c intrinsics/abort.c \
 	intrinsics/args.c intrinsics/cshift0.c intrinsics/eoshift0.c \
@@ -1550,6 +1552,7 @@ distclean-compile:
 @AMDEP_TRUE@@am__include@ @am__quote@./$(DEPDIR)/any_l8.Plo@am__quote@
 @AMDEP_TRUE@@am__include@ @am__quote@./$(DEPDIR)/args.Plo@am__quote@
 @AMDEP_TRUE@@am__include@ @am__quote@./$(DEPDIR)/associated.Plo@am__quote@
+@AMDEP_TRUE@@am__include@ @am__quote@./$(DEPDIR)/async.Plo@am__quote@
 @AMDEP_TRUE@@am__include@ @am__quote@./$(DEPDIR)/backtrace.Plo@am__quote@
 @AMDEP_TRUE@@am__include@ @am__quote@./$(DEPDIR)/bessel_r10.Plo@am__quote@
 @AMDEP_TRUE@@am__include@ @am__quote@./$(DEPDIR)/bessel_r16.Plo@am__quote@
@@ -5813,6 +5816,13 @@ fbuf.lo: io/fbuf.c
 @AMDEP_TRUE@@am__fastdepCC_FALSE@	DEPDIR=$(DEPDIR) $(CCDEPMODE) $(depcomp) @AMDEPBACKSLASH@
 @am__fastdepCC_FALSE@	$(LIBTOOL)  --tag=CC $(AM_LIBTOOLFLAGS) $(LIBTOOLFLAGS) --mode=compile $(CC) $(DEFS) $(DEFAULT_INCLUDES) $(INCLUDES) $(AM_CPPFLAGS) $(CPPFLAGS) $(AM_CFLAGS) $(CFLAGS) -c -o fbuf.lo `test -f 'io/fbuf.c' || echo '$(srcdir)/'`io/fbuf.c
 
+async.lo: io/async.c
+@am__fastdepCC_TRUE@	$(LIBTOOL)  --tag=CC $(AM_LIBTOOLFLAGS) $(LIBTOOLFLAGS) --mode=compile $(CC) $(DEFS) $(DEFAULT_INCLUDES) $(INCLUDES) $(AM_CPPFLAGS) $(CPPFLAGS) $(AM_CFLAGS) $(CFLAGS) -MT async.lo -MD -MP -MF $(DEPDIR)/async.Tpo -c -o async.lo `test -f 'io/async.c' || echo '$(srcdir)/'`io/async.c
+@am__fastdepCC_TRUE@	$(am__mv) $(DEPDIR)/async.Tpo $(DEPDIR)/async.Plo
+@AMDEP_TRUE@@am__fastdepCC_FALSE@	source='io/async.c' object='async.lo' libtool=yes @AMDEPBACKSLASH@
+@AMDEP_TRUE@@am__fastdepCC_FALSE@	DEPDIR=$(DEPDIR) $(CCDEPMODE) $(depcomp) @AMDEPBACKSLASH@
+@am__fastdepCC_FALSE@	$(LIBTOOL)  --tag=CC $(AM_LIBTOOLFLAGS) $(LIBTOOLFLAGS) --mode=compile $(CC) $(DEFS) $(DEFAULT_INCLUDES) $(INCLUDES) $(AM_CPPFLAGS) $(CPPFLAGS) $(AM_CFLAGS) $(CFLAGS) -c -o async.lo `test -f 'io/async.c' || echo '$(srcdir)/'`io/async.c
+
 associated.lo: intrinsics/associated.c
 @am__fastdepCC_TRUE@	$(LIBTOOL)  --tag=CC $(AM_LIBTOOLFLAGS) $(LIBTOOLFLAGS) --mode=compile $(CC) $(DEFS) $(DEFAULT_INCLUDES) $(INCLUDES) $(AM_CPPFLAGS) $(CPPFLAGS) $(AM_CFLAGS) $(CFLAGS) -MT associated.lo -MD -MP -MF $(DEPDIR)/associated.Tpo -c -o associated.lo `test -f 'intrinsics/associated.c' || echo '$(srcdir)/'`intrinsics/associated.c
 @am__fastdepCC_TRUE@	$(am__mv) $(DEPDIR)/associated.Tpo $(DEPDIR)/associated.Plo
Index: libgfortran/gfortran.map
===================================================================
--- libgfortran/gfortran.map	(Revision 259739)
+++ libgfortran/gfortran.map	(Arbeitskopie)
@@ -1482,3 +1482,8 @@ GFORTRAN_C99_8 {
     y1f;
     ynf;
 };
+
+GFORTRAN_9 {
+  global:
+  _gfortran_st_wait_async;
+};
Index: libgfortran/io/async.c
===================================================================
--- libgfortran/io/async.c	(nicht existent)
+++ libgfortran/io/async.c	(Arbeitskopie)
@@ -0,0 +1,401 @@
+/* Copyright (C) 2018 Free Software Foundation, Inc.
+   Contributed by Nicolas Koenig
+
+This file is part of the GNU Fortran runtime library (libgfortran).
+
+Libgfortran 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, or (at your option)
+any later version.
+
+Libgfortran 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.
+
+Under Section 7 of GPL version 3, you are granted additional
+permissions described in the GCC Runtime Library Exception, version
+3.1, as published by the Free Software Foundation.
+
+You should have received a copy of the GNU General Public License and
+a copy of the GCC Runtime Library Exception along with this program;
+see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see
+<http://www.gnu.org/licenses/>.  */
+
+#include "libgfortran.h"
+
+#ifndef GTHREAD_USE_WEAK
+#ifdef SUPPORTS_WEAK
+#define GTHREAD_USE_WEAK 1
+#endif
+#endif
+
+#define _GTHREAD_USE_COND_INIT_FUNC
+#include "../../libgcc/gthr-posix.h"
+#include "io.h"
+#include "fbuf.h"
+#include "format.h"
+#include "unix.h"
+#include <string.h>
+#include <assert.h>
+
+#include <sys/types.h>
+
+#include "async.h"
+
+DEBUG_LINE(__thread const char *aio_prefix = MPREFIX);
+
+DEBUG_LINE(__gthread_mutex_t debug_queue_lock = __GTHREAD_MUTEX_INIT;)
+DEBUG_LINE(aio_lock_debug *aio_debug_head = NULL;)
+
+__thread gfc_unit *thread_unit = NULL;
+
+typedef struct transfer_queue
+{
+  enum aio_do type;
+  struct transfer_queue *next;
+  struct st_parameter_dt *new_pdt;
+  transfer_args arg;
+  _Bool has_id;
+} transfer_queue;
+
+struct error {
+  st_parameter_dt *dtp;
+  int id;
+};
+
+static void
+update_pdt(st_parameter_dt **old, st_parameter_dt *new) {
+  st_parameter_dt *temp;
+  NOTE("Changing pdts");
+  temp = *old;
+  *old = new;
+  if(temp)
+    free(temp);
+}
+
+static void
+destroy_adv_cond (struct adv_cond * ac)
+{
+  T_ERROR (__gthread_mutex_destroy, &ac->lock);
+  T_ERROR (__gthread_cond_destroy, &ac->signal);
+}
+
+static void *
+async_io (void *arg)
+{
+  DEBUG_LINE(aio_prefix = TPREFIX);
+  transfer_queue *ctq = NULL, *prev = NULL;
+  gfc_unit *u = (gfc_unit *) arg;
+  async_unit *au = u->au;
+  thread_unit = u;
+  LOCK (&au->lock);
+  au->thread = __gthread_self ();
+  UNLOCK (&au->lock);
+  while (true)
+    {
+      WAIT_SIGNAL (&au->work, au->tail || au->finished);
+      LOCK (&au->lock);
+      ctq = au->head;
+      prev = NULL;
+      while (ctq)
+	{
+	  if (prev)
+	    free (prev);
+	  prev = ctq;
+	  if (!au->error.has_error)
+	    {
+	      UNLOCK (&au->lock);
+	  
+	      switch(ctq->type)
+		{
+		case AIO_WRITE_DONE:
+		  NOTE("Finalizing write");
+		  st_write_done_worker (au->pdt); 
+		  break;
+		case AIO_READ_DONE:
+		  NOTE("Finalizing read");
+		  st_read_done_worker (au->pdt);
+		  break;
+		case AIO_CHANGE_PDT: 
+		  update_pdt(&au->pdt, ctq->new_pdt); 
+		  break; 
+		case AIO_TRANSFER_SCALAR:
+		  NOTE("Starting scalar transfer");
+		  ctq->arg.scalar.transfer (au->pdt, ctq->arg.scalar.arg_bt, 
+					    ctq->arg.scalar.data,
+					    ctq->arg.scalar.i,
+					    ctq->arg.scalar.s1,
+					    ctq->arg.scalar.s2);
+		  break;
+		case AIO_TRANSFER_ARRAY:
+		  NOTE("Starting array transfer");
+		  NOTE("ctq->arg.array.desc = %p", (void *) (ctq->arg.array.desc));
+		  transfer_array_inner(au->pdt, ctq->arg.array.desc, 
+				       ctq->arg.array.kind, 
+				       ctq->arg.array.charlen);
+		  		  NOTE("desc = %p", (void *) ctq->arg.array.desc);
+		  		  free (ctq->arg.array.desc);
+		  break;
+		default:
+		  internal_error(NULL, "Invalid queue type");
+		  break;
+		}
+	      LOCK (&au->lock);
+	      if (unlikely (au->error.has_error))
+		{
+		  au->error.last_good_id = au->id.low - 1;
+		  unlock_unit (au->pdt->u.p.current_unit);
+		}
+	    }
+  	  NOTE("Current id: %d", au->id.low);
+  	  if (ctq->has_id && au->id.waiting == au->id.low++)
+	    SIGNAL (&au->id.done);
+	  ctq = ctq->next;
+	}
+      au->tail = NULL;
+      au->head = NULL;
+      SIGNAL (&au->emptysignal);
+      au->empty = 1;
+      if (au->finished)
+	break;
+      UNLOCK (&au->lock);
+    }
+  UNLOCK (&au->lock);
+  return NULL;
+}
+
+
+static void
+free_async_unit (async_unit * au)
+{
+  if (au->tail)
+	internal_error(NULL, "Trying to free nonempty unit");
+  destroy_adv_cond (&au->work);
+  destroy_adv_cond (&au->emptysignal);
+  destroy_adv_cond (&au->id.done);
+  T_ERROR (__gthread_mutex_destroy, &au->lock);
+  free (au);
+}
+
+static void
+init_adv_cond (struct adv_cond * ac)
+{
+  ac->pending = 0;
+  __GTHREAD_MUTEX_INIT_FUNCTION(&ac->lock);
+  __gthread_cond_init_function (&ac->signal);
+}
+
+async_unit *
+init_async_unit (gfc_unit *u)
+{
+  async_unit *au;
+  if (!__gthread_active_p ())
+    return NULL;
+
+  au = (async_unit *) xmalloc (sizeof (async_unit));
+  u->au = au;
+  init_adv_cond (&au->work);
+  init_adv_cond (&au->emptysignal);
+  __GTHREAD_MUTEX_INIT_FUNCTION(&au->lock);
+  T_ERROR (__gthread_create, &au->thread, &async_io, (void *) u);
+  au->pdt = NULL;
+  au->head = NULL;
+  au->tail = NULL;
+  au->empty = true;
+  au->finished = 0;
+  au->id.waiting = -1;
+  au->id.low = 0;
+  au->id.high = 0;
+  au->error.fatal_error = 0;
+  au->error.has_error = 0;
+  au->error.last_good_id = 0;
+  init_adv_cond (&au->id.done);
+  return au;
+}
+
+
+void
+enqueue_transfer (async_unit * au, transfer_args * arg, enum aio_do type)
+{
+  transfer_queue *tq = calloc (sizeof (transfer_queue), 1);
+  tq->arg = *arg;
+  tq->type = type;
+  tq->has_id = 0;
+  LOCK (&au->lock);
+  if (!au->tail)
+    au->head = tq;
+  else
+    au->tail->next = tq;
+  au->tail = tq;
+  REVOKE_SIGNAL (&(au->emptysignal));
+  au->empty = false;
+  UNLOCK (&au->lock);
+  SIGNAL(&au->work);
+}
+
+int
+enqueue_done_id (async_unit *au, enum aio_do type) {
+  int ret;
+  transfer_queue *tq = calloc (sizeof (transfer_queue), 1);
+
+  tq->type = type;
+  tq->has_id = 1;
+  LOCK (&au->lock);
+  if (!au->tail)
+    au->head = tq;
+  else
+    au->tail->next = tq;
+  au->tail = tq;
+  REVOKE_SIGNAL (&(au->emptysignal));
+  au->empty = false;
+  ret = au->id.high++;
+  NOTE("Enqueue id: %d", ret)
+  UNLOCK(&au->lock);
+  SIGNAL(&au->work);  
+  return ret;
+}
+
+void
+enqueue_done (async_unit *au, enum aio_do type)
+{
+  transfer_queue *tq = calloc (sizeof (transfer_queue), 1);
+  tq->type = type;
+  tq->has_id = 0;
+  LOCK (&au->lock);
+  if (!au->tail)
+    au->head = tq;
+  else
+    au->tail->next = tq;
+  au->tail = tq;
+  REVOKE_SIGNAL (&(au->emptysignal));
+  au->empty = false;
+  UNLOCK (&au->lock);
+  SIGNAL(&au->work);  
+}
+
+void
+change_pdt (async_unit *au, st_parameter_dt *dt) {
+  st_parameter_dt *new = xmalloc(sizeof(st_parameter_dt));
+  transfer_queue *tq = xmalloc(sizeof(transfer_queue));
+  memcpy((void *) new, (void *) dt, sizeof(st_parameter_dt));
+  tq->next = NULL;
+  tq->new_pdt = new;
+  tq->type = AIO_CHANGE_PDT;
+  tq->has_id = 0;
+  LOCK(&au->lock);
+  if (!au->tail)
+    au->head = tq;
+  else
+    au->tail->next = tq;
+  au->tail = tq;
+  REVOKE_SIGNAL (&(au->emptysignal));
+  au->empty = 0;
+  UNLOCK(&au->lock);
+  SIGNAL(&au->work);
+}
+
+/* Perform a wait operation on an asynchronous unit, which means collecting
+   the errors that may have happened asynchronously.  Return true if an error
+   has been encountered.  */
+
+static bool
+async_wait_operation (st_parameter_common *cmp, async_unit *au)
+{
+  bool has_error = au->error.has_error;
+
+  if (has_error)
+    {
+      if (generate_error_common (cmp, au->error.family, au->error.message))
+	{
+	  au->error.has_error = 0;
+	  au->error.cmp = NULL;
+	}
+      else
+	{
+	  /* The program will exit later.  */
+	  au->error.fatal_error = true;
+	}
+    }
+  return has_error;
+}
+
+/* Perform a wait operation on an asynchronous unit with an ID specified,
+   which means collecting the errors that may have happened asynchronously.
+   Return true if an error has been encountered.  */
+
+bool
+async_wait_id (st_parameter_common *cmp, async_unit * au, int i)
+{
+  bool ret;
+
+  if (au == NULL)
+    return false;
+
+  if (cmp == NULL)
+    cmp = au->error.cmp;
+
+  if (au->error.has_error)
+    {
+      if (i <= au->error.last_good_id)
+	return false;
+
+      return async_wait_operation (cmp, au);
+    }
+
+  LOCK (&au->lock);
+  NOTE("Waiting for id %d", i);
+  if (au->id.waiting < i)
+    au->id.waiting = i;
+  UNLOCK (&au->lock);
+  SIGNAL (&(au->work));
+  WAIT_SIGNAL (&(au->id.done), (au->id.low >= au->id.waiting || au->empty));
+  LOCK (&au->lock);
+  ret = async_wait_operation (cmp, au);
+  UNLOCK(&au->lock);
+  return ret;
+}
+
+bool
+async_wait (st_parameter_common *cmp, async_unit * au)
+{
+  bool ret;
+
+  if (au == NULL)
+    return false;
+
+  if (cmp == NULL)
+    cmp = au->error.cmp;
+
+  SIGNAL (&(au->work));
+  LOCK(&au->lock);
+  if (au->empty)
+    {
+      ret = async_wait_operation (cmp, au);
+      UNLOCK(&au->lock);
+      return ret;
+    }
+
+  UNLOCK(&au->lock);  
+  WAIT_SIGNAL (&(au->emptysignal), (au->empty));
+  LOCK (&au->lock);
+  ret = async_wait_operation (cmp, au);
+  UNLOCK(&au->lock);
+  return ret;
+}
+
+void
+async_close (async_unit * au)
+{
+  NOTE("Closing async unit");
+  if (!au->error.fatal_error)
+    {
+      LOCK (&au->lock);
+      au->finished = 1;
+      UNLOCK (&au->lock);
+      NOTE ("About to wait in async_close");
+      async_wait (NULL, au);
+      T_ERROR (__gthread_join, au->thread, NULL);
+    }
+  free_async_unit(au);
+}
Index: libgfortran/io/async.h
===================================================================
--- libgfortran/io/async.h	(nicht existent)
+++ libgfortran/io/async.h	(Arbeitskopie)
@@ -0,0 +1,332 @@
+/* Copyright (C) 2018 Free Software Foundation, Inc.
+   Contributed by Nicolas Koenig
+
+This file is part of the GNU Fortran runtime library (libgfortran).
+
+Libgfortran 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, or (at your option)
+any later version.
+
+Libgfortran 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.
+
+Under Section 7 of GPL version 3, you are granted additional
+permissions described in the GCC Runtime Library Exception, version
+3.1, as published by the Free Software Foundation.
+
+You should have received a copy of the GNU General Public License and
+a copy of the GCC Runtime Library Exception along with this program;
+see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see
+<http://www.gnu.org/licenses/>.  */
+
+#ifndef ASYNC_H
+#define ASYNC_H
+
+#define DEBUG_ASYNC
+#undef DEBUG_ASYNC
+
+#ifdef DEBUG_ASYNC
+
+#define DEBUG_PRINTF(...) fprintf(stderr,__VA_ARGS__)
+
+#define IN_DEBUG_QUEUE(mutex) ({\
+	__label__ end;\
+	aio_lock_debug *curr = aio_debug_head;\
+	while(curr) { \
+	  if (curr->m == mutex) {\
+	    goto end;\
+	  }\
+	  curr = curr->next;\
+	}\
+	end:;\
+	curr;\
+	})
+
+#define TAIL_DEBUG_QUEUE ({\
+      aio_lock_debug *curr = aio_debug_head;	\
+	while(curr && curr->next) { \
+	  curr = curr->next;\
+	}\
+	curr;\
+	})
+
+#define CHECK_LOCK(mutex, status) do {\
+	aio_lock_debug *curr;\
+	INTERN_LOCK(&debug_queue_lock);		\
+	if (__gthread_mutex_trylock(mutex)) {\
+	  if ((curr = IN_DEBUG_QUEUE(mutex))) {\
+	    sprintf(status, "\033[31m%s():%d\033[0m", curr->func, curr->line);\
+	  } else\
+	    sprintf(status, "\033[31munknown\033[0m");\
+        }\
+	else {\
+	  __gthread_mutex_unlock(mutex);\
+	  sprintf(status, "\033[32munlocked\033[0m");\
+	}\
+	INTERN_UNLOCK(&debug_queue_lock);\
+	}while(0)
+
+#define T_ERROR(func, ...) do {\
+	int t_error_temp; \
+	t_error_temp = func(__VA_ARGS__);\
+	if(t_error_temp)\
+	  ERROR(t_error_temp, "args: " #__VA_ARGS__ "\n");\
+	} while(0)
+
+#define NOTE(str, ...) do{\
+	char note_str[200];\
+	sprintf(note_str, "%s\033[35mNOTE: \033[0m" str, aio_prefix, ##__VA_ARGS__);\
+	DEBUG_PRINTF("%-90s %20s():5%d\n", note_str, __FUNCTION__, __LINE__);\
+	}while(0);
+
+#define ERROR(errnum, str, ...) do{\
+	char note_str[200];\
+	sprintf(note_str, "%s\033[41;37mERROR:\033[0m [%d] " str, aio_prefix, \
+	  errnum, ##__VA_ARGS__);\
+	DEBUG_PRINTF("%-68s %s():%d\n", note_str, __FUNCTION__, __LINE__);\
+	}while(0)
+
+#define MUTEX_DEBUG_ADD(mutex) do {\
+	aio_lock_debug *n;\
+	n = malloc(sizeof(aio_lock_debug));\
+	n->prev = TAIL_DEBUG_QUEUE;\
+	if (n->prev) \
+	  n->prev->next = n; \
+	n->next = NULL;\
+	n->line = __LINE__;\
+	n->func = __FUNCTION__;\
+	n->m = mutex;\
+	if (!aio_debug_head) {\
+	  aio_debug_head = n;\
+	}\
+	} while(0)
+
+#define UNLOCK(mutex) do {\
+	aio_lock_debug *curr;\
+	DEBUG_PRINTF("%s%-75s %20s():%-5d %18p\n", aio_prefix, "\033[32mUNLOCK: \033[0m" #mutex, \
+		     __FUNCTION__, __LINE__, (void *) mutex);		\
+        INTERN_LOCK(&debug_queue_lock);\
+	curr = IN_DEBUG_QUEUE(mutex);\
+	if (curr) \
+	  {\
+	    if (curr->prev)\
+	      curr->prev->next = curr->next;\
+	    if (curr->next) {\
+	      curr->next->prev = curr->prev;\
+	      if (curr == aio_debug_head)\
+		aio_debug_head = curr->next;\
+	    } else {\
+	      if (curr == aio_debug_head)\
+	        aio_debug_head = NULL;\
+	    }\
+	    free(curr);\
+	  }\
+	INTERN_UNLOCK(&debug_queue_lock);\
+	INTERN_UNLOCK(mutex);\
+	}while(0)
+
+#define TRYLOCK(mutex) ({\
+	char status[200];\
+	int res;\
+	aio_lock_debug *curr;\
+	res = __gthread_mutex_trylock(mutex);\
+	INTERN_LOCK(&debug_queue_lock);		\
+	if (res) {\
+	  if ((curr = IN_DEBUG_QUEUE(mutex))) {\
+	    sprintf(status, "\033[31m%s():%d\033[0m", curr->func, curr->line);\
+	  } else\
+	    sprintf(status, "\033[31munknown\033[0m");\
+        }\
+	else {\
+	  sprintf(status, "\033[32munlocked\033[0m");\
+	  MUTEX_DEBUG_ADD(mutex);\
+	}\
+	DEBUG_PRINTF("%s%-44s prev: %-35s %20s():%-5d %18p\n", aio_prefix, \
+	  "\033[31;2mTRYLOCK: \033[0m" #mutex, status, __FUNCTION__, __LINE__,\
+	  (void *) mutex);\
+	INTERN_UNLOCK(&debug_queue_lock);\
+	res;\
+	})
+
+#define LOCK(mutex) do {\
+	char status[200];\
+	CHECK_LOCK(mutex, status);\
+	DEBUG_PRINTF("%s%-42s prev: %-35s %20s():%-5d %18p\n", aio_prefix, \
+		     "\033[31mLOCK: \033[0m" #mutex, status, __FUNCTION__, __LINE__, (void *) mutex); \
+	INTERN_LOCK(mutex);\
+	INTERN_LOCK(&debug_queue_lock);	\
+	MUTEX_DEBUG_ADD(mutex);\
+	INTERN_UNLOCK(&debug_queue_lock);\
+	DEBUG_PRINTF("%s\033[31mACQ:\033[0m %-30s %78p\n", aio_prefix, #mutex, mutex); \
+	}while(0)
+
+#define DEBUG_LINE(...) __VA_ARGS__ 
+
+#else
+#define DEBUG_PRINTF(...) {}
+#define CHECK_LOCK(au, mutex, status) {}
+#define NOTE(str, ...) {}
+#define DEBUG_LINE(...)
+#define T_ERROR(func, ...) func(__VA_ARGS__)
+#define LOCK(mutex) INTERN_LOCK(mutex)
+#define UNLOCK(mutex) INTERN_UNLOCK(mutex)
+#define TRYLOCK(mutex) (__gthread_mutex_trylock(mutex))
+#endif
+
+#define MPREFIX "\033[30;46mM:\033[0m "
+#define TPREFIX "\033[37;44mT:\033[0m "
+#define RPREFIX "\033[37;41mR:\033[0m "
+
+#define INTERN_LOCK(mutex) T_ERROR(__gthread_mutex_lock, mutex);
+
+#define INTERN_UNLOCK(mutex) T_ERROR(__gthread_mutex_unlock, mutex);
+
+#define SIGNAL(advcond) do{\
+	INTERN_LOCK(&(advcond)->lock);\
+	(advcond)->pending = 1;\
+	INTERN_UNLOCK(&(advcond)->lock);\
+	DEBUG_PRINTF("%s%-75s %20s():%-5d %18p\n", aio_prefix, "\033[33mSIGNAL: \033[0m" \
+	  #advcond, __FUNCTION__, __LINE__, (void *) advcond);\
+	T_ERROR(__gthread_cond_broadcast, &(advcond)->signal);\
+	}while(0)
+
+#define WAIT_SIGNAL(advcond, condition) do{\
+	__label__ finish;\
+	INTERN_LOCK(&((advcond)->lock));\
+	DEBUG_PRINTF("%s%-75s %20s():%-5d %18p\n", aio_prefix, "\033[34mWAITING: \033[0m" \
+	  #advcond, __FUNCTION__, __LINE__, (void *) advcond);\
+	if ((advcond)->pending){\
+	  goto finish;\
+ 	}\
+	if ( condition ) {\
+	  goto finish; \
+	}\
+	while(!__gthread_cond_wait(&(advcond)->signal, &(advcond)->lock)) {\
+	  if ( condition ){\
+	    DEBUG_PRINTF("%s%-75s %20s():%-5d %18p\n", aio_prefix, "\033[33mREC: \033[0m" \
+		   #advcond,  __FUNCTION__, __LINE__, (void *)advcond);\
+	    break;\
+	  }\
+	}\
+	finish: \
+	(advcond)->pending = 0;\
+	INTERN_UNLOCK(&((advcond)->lock));\
+	}while(0)
+
+#define REVOKE_SIGNAL(advcond) do{\
+	INTERN_LOCK(&(advcond)->lock);\
+	(advcond)->pending = 0;\
+	INTERN_UNLOCK(&(advcond)->lock);\
+	}while(0)
+
+DEBUG_LINE(extern __thread const char *aio_prefix);
+
+DEBUG_LINE(typedef struct aio_lock_debug{
+	__gthread_mutex_t *m;
+	int line;	
+	const char *func;
+	struct aio_lock_debug *next;	
+	struct aio_lock_debug *prev;
+} aio_lock_debug;)
+
+DEBUG_LINE(extern aio_lock_debug *aio_debug_head;)
+DEBUG_LINE(extern __gthread_mutex_t debug_queue_lock;)
+
+extern __thread gfc_unit *thread_unit;
+
+enum aio_do {
+  AIO_INVALID = 0,
+  AIO_CHANGE_PDT,
+  AIO_TRANSFER_SCALAR,
+  AIO_TRANSFER_ARRAY,
+  AIO_WRITE_DONE,
+  AIO_READ_DONE
+};
+
+typedef union transfer_args
+{
+  struct 
+  { 
+    void (*transfer) (struct st_parameter_dt *, bt, void *, int, size_t, size_t);
+    bt arg_bt;
+    void *data;
+    int i;
+    size_t s1;
+    size_t s2;
+  } scalar;
+  struct 
+  {
+    gfc_array_char *desc;
+    int kind;
+    gfc_charlen_type charlen;
+  } array;
+} transfer_args;
+
+struct adv_cond
+{
+  int pending;
+  __gthread_mutex_t lock;
+  __gthread_cond_t signal;
+};
+
+typedef struct async_unit
+{
+  pthread_mutex_t lock;
+  struct adv_cond work;
+  struct adv_cond emptysignal;
+  struct st_parameter_dt *pdt;
+  pthread_t thread;
+  struct transfer_queue *head;
+  struct transfer_queue *tail;
+  struct
+  {
+    int waiting;
+    int low;
+    int high;
+    struct adv_cond done;
+  } id;
+
+  int finished;
+  bool empty;
+
+  struct {
+    const char *message;
+    st_parameter_common *cmp;
+    bool has_error;
+    int last_good_id;
+    int family;
+    bool fatal_error;
+  } error;
+
+} async_unit;
+
+async_unit *init_async_unit(gfc_unit *);
+internal_proto (init_async_unit);
+
+bool async_wait (st_parameter_common *, async_unit *);
+internal_proto(async_wait);
+
+bool async_wait_id (st_parameter_common *, async_unit *, int);
+internal_proto(async_wait_id);
+
+void async_close (async_unit *);
+internal_proto(async_close);
+
+void enqueue_transfer (async_unit * au, transfer_args * arg, enum aio_do);
+internal_proto(enqueue_transfer);
+
+void enqueue_done (async_unit *, enum aio_do type);
+internal_proto(enqueue_done);
+
+int enqueue_done_id (async_unit *, enum aio_do type);
+internal_proto(enqueue_done_id);
+
+void enqueue_init (async_unit *);
+internal_proto(enqueue_init);
+
+void change_pdt(async_unit *, st_parameter_dt *);
+internal_proto(change_pdt);
+#endif
Index: libgfortran/io/close.c
===================================================================
--- libgfortran/io/close.c	(Revision 259739)
+++ libgfortran/io/close.c	(Arbeitskopie)
@@ -24,6 +24,7 @@ see the files COPYING3 and COPYING.RUNTIME respect
 
 #include "io.h"
 #include "unix.h"
+#include "async.h"
 #include <limits.h>
 
 typedef enum
@@ -57,6 +58,15 @@ st_close (st_parameter_close *clp)
     find_option (&clp->common, clp->status, clp->status_len,
 		 status_opt, "Bad STATUS parameter in CLOSE statement");
 
+  u = find_unit (clp->common.unit);
+
+  if (u && u->au)
+    if (async_wait (&(clp->common), u->au))
+      {
+	library_end();
+	return;
+      }
+
   if ((clp->common.flags & IOPARM_LIBRETURN_MASK) != IOPARM_LIBRETURN_OK)
   {
     library_end ();
@@ -63,7 +73,6 @@ st_close (st_parameter_close *clp)
     return;
   }
 
-  u = find_unit (clp->common.unit);
   if (u != NULL)
     {
       if (close_share (u) < 0)
Index: libgfortran/io/file_pos.c
===================================================================
--- libgfortran/io/file_pos.c	(Revision 259739)
+++ libgfortran/io/file_pos.c	(Arbeitskopie)
@@ -25,6 +25,7 @@ see the files COPYING3 and COPYING.RUNTIME respect
 #include "io.h"
 #include "fbuf.h"
 #include "unix.h"
+#include "async.h"
 #include <string.h>
 
 /* file_pos.c-- Implement the file positioning statements, i.e. BACKSPACE,
@@ -214,6 +215,9 @@ st_backspace (st_parameter_filepos *fpp)
       goto done;
     }
 
+  if (u->au && async_wait (&(fpp->common), u->au))
+    return;
+
   /* Make sure format buffer is flushed and reset.  */
   if (u->flags.form == FORM_FORMATTED)
     {
@@ -294,6 +298,9 @@ st_endfile (st_parameter_filepos *fpp)
 	  goto done;
 	}
 
+      if (u->au && async_wait (&(fpp->common), u->au))
+	return;
+
       if (u->flags.access == ACCESS_SEQUENTIAL
       	  && u->endfile == AFTER_ENDFILE)
 	{
@@ -401,6 +408,10 @@ st_rewind (st_parameter_filepos *fpp)
 			"Cannot REWIND a file opened for DIRECT access");
       else
 	{
+
+	  if (u->au && async_wait (&(fpp->common), u->au))
+	    return;
+
 	  /* If there are previously written bytes from a write with ADVANCE="no",
 	     add a record marker before performing the ENDFILE.  */
 
@@ -456,6 +467,9 @@ st_flush (st_parameter_filepos *fpp)
   u = find_unit (fpp->common.unit);
   if (u != NULL)
     {
+      if (u->au && async_wait (&(fpp->common), u->au))
+	return;
+
       /* Make sure format buffer is flushed.  */
       if (u->flags.form == FORM_FORMATTED)
         fbuf_flush (u, u->mode);
Index: libgfortran/io/inquire.c
===================================================================
--- libgfortran/io/inquire.c	(Revision 259739)
+++ libgfortran/io/inquire.c	(Arbeitskopie)
@@ -26,6 +26,7 @@ see the files COPYING3 and COPYING.RUNTIME respect
 /* Implement the non-IOLENGTH variant of the INQUIRY statement */
 
 #include "io.h"
+#include "async.h"
 #include "unix.h"
 #include <string.h>
 
@@ -281,12 +282,6 @@ inquire_via_unit (st_parameter_inquire *iqp, gfc_u
     {
       GFC_INTEGER_4 cf2 = iqp->flags2;
 
-      if ((cf2 & IOPARM_INQUIRE_HAS_PENDING) != 0)
-	*iqp->pending = 0;
-  
-      if ((cf2 & IOPARM_INQUIRE_HAS_ID) != 0)
-        *iqp->id = 0;
-
       if ((cf2 & IOPARM_INQUIRE_HAS_ENCODING) != 0)
 	{
 	  if (u == NULL || u->flags.form != FORM_FORMATTED)
@@ -347,6 +342,27 @@ inquire_via_unit (st_parameter_inquire *iqp, gfc_u
 	  cf_strcpy (iqp->asynchronous, iqp->asynchronous_len, p);
 	}
 
+      if ((cf2 & IOPARM_INQUIRE_HAS_PENDING) != 0)
+	{
+	  if (u->au == NULL)
+	    *(iqp->pending) = 0;
+	  else
+	    {
+	      LOCK (&(u->au->lock));
+	      if ((cf2 & IOPARM_INQUIRE_HAS_ID) != 0)
+		{
+		  int id;
+		  id = *(iqp->id);
+		  *(iqp->pending) = id > u->au->id.low;
+		}
+	      else
+		{
+		  *(iqp->pending) = ! u->au->empty;
+		}
+	      UNLOCK (&(u->au->lock));
+	    }
+	}
+
       if ((cf2 & IOPARM_INQUIRE_HAS_SIGN) != 0)
 	{
 	  if (u == NULL)
Index: libgfortran/io/io.h
===================================================================
--- libgfortran/io/io.h	(Revision 259739)
+++ libgfortran/io/io.h	(Arbeitskopie)
@@ -531,7 +531,9 @@ typedef struct st_parameter_dt
 	  /* A flag used to identify when a non-standard expanded namelist read
 	     has occurred.  */
 	  unsigned expanded_read : 1;
-	  /* 13 unused bits.  */
+	  /* Flag to indicate if the statement has async="YES". */
+	  unsigned async : 1;
+	  /* 12 unused bits.  */
 
 	  int child_saved_iostat;
 	  int nml_delim;
@@ -590,7 +592,7 @@ extern char check_st_parameter_dt[sizeof (((st_par
 typedef struct
 {
   st_parameter_common common;
-  CHARACTER1 (id);
+  GFC_INTEGER_4 *id;
 }
 st_parameter_wait;
 
@@ -659,6 +661,9 @@ typedef struct gfc_unit
 
   int continued;
 
+  /* contains the pointer to the async unit */
+  struct async_unit *au;
+
   __gthread_mutex_t lock;
   /* Number of threads waiting to acquire this unit's lock.
      When non-zero, close_unit doesn't only removes the unit
@@ -817,9 +822,16 @@ internal_proto(next_record);
 extern void st_wait (st_parameter_wait *);
 export_proto(st_wait);
 
+extern void st_wait_async (st_parameter_wait *);
+export_proto(st_wait_async);
+
 extern void hit_eof (st_parameter_dt *);
 internal_proto(hit_eof);
 
+extern void transfer_array_inner (st_parameter_dt *, gfc_array_char *, int,
+				  gfc_charlen_type);
+internal_proto(transfer_array_inner);
+
 /* read.c */
 
 extern void set_integer (void *, GFC_INTEGER_LARGEST, int);
@@ -988,3 +1000,10 @@ memset4 (gfc_char4_t *p, gfc_char4_t c, int k)
 
 #endif
 
+extern void
+st_write_done_worker (st_parameter_dt *dtp);
+internal_proto (st_write_done_worker);
+
+extern void
+st_read_done_worker (st_parameter_dt *dtp);
+internal_proto (st_read_done_worker);
Index: libgfortran/io/open.c
===================================================================
--- libgfortran/io/open.c	(Revision 259739)
+++ libgfortran/io/open.c	(Arbeitskopie)
@@ -26,6 +26,7 @@ see the files COPYING3 and COPYING.RUNTIME respect
 #include "io.h"
 #include "fbuf.h"
 #include "unix.h"
+#include "async.h"
 
 #ifdef HAVE_UNISTD_H
 #include <unistd.h>
@@ -651,8 +652,12 @@ new_unit (st_parameter_open *opp, gfc_unit *u, uni
   else
     u->fbuf = NULL;
 
-    
-    
+  /* Check if asynchrounous.  */
+  if (flags->async == ASYNC_YES)
+    u->au = init_async_unit (u);  
+  else
+    u->au = NULL;
+
   return u;
 
  cleanup:
Index: libgfortran/io/transfer.c
===================================================================
--- libgfortran/io/transfer.c	(Revision 259739)
+++ libgfortran/io/transfer.c	(Arbeitskopie)
@@ -31,6 +31,7 @@ see the files COPYING3 and COPYING.RUNTIME respect
 #include "fbuf.h"
 #include "format.h"
 #include "unix.h"
+#include "async.h"
 #include <string.h>
 #include <errno.h>
 
@@ -184,6 +185,12 @@ static const st_option pad_opt[] = {
   {NULL, 0}
 };
 
+static const st_option async_opt[] = {
+  {"yes", ASYNC_YES},
+  {"no", ASYNC_NO},
+  {NULL, 0}
+};
+
 typedef enum
 { FORMATTED_SEQUENTIAL, UNFORMATTED_SEQUENTIAL,
   FORMATTED_DIRECT, UNFORMATTED_DIRECT, FORMATTED_STREAM, UNFORMATTED_STREAM
@@ -2281,7 +2288,38 @@ formatted_transfer (st_parameter_dt *dtp, bt type,
     }
 }
 
+/* Wrapper function for I/O of scalar types.  If this should be an async I/O
+   request, queue it. For a synchronous write on an async unit, perform the
+   wait operation and return an error.  For all synchronous writes, call the
+   right transfer function.  */
 
+static void
+wrap_scalar_transfer (st_parameter_dt *dtp, bt type, void *p, int kind,
+		      size_t size, size_t n_elem)
+{
+  if (dtp->u.p.current_unit && dtp->u.p.current_unit->au)
+    {
+      if (dtp->u.p.async)
+	{
+	  transfer_args args;
+	  args.scalar.transfer = dtp->u.p.transfer;
+	  args.scalar.arg_bt = type;
+	  args.scalar.data = p;
+	  args.scalar.i = kind;
+	  args.scalar.s1 = size;
+	  args.scalar.s2 = n_elem;
+	  enqueue_transfer(dtp->u.p.current_unit->au, &args, AIO_TRANSFER_SCALAR);
+	  return;
+	}
+    }
+  /* Come here if there was no asynchronous I/O to be scheduled.  */
+  if ((dtp->common.flags & IOPARM_LIBRETURN_MASK) != IOPARM_LIBRETURN_OK)
+    return;
+
+  dtp->u.p.transfer (dtp, type, p, kind, size, 1);
+}
+
+
 /* Data transfer entry points.  The type of the data entity is
    implicit in the subroutine call.  This prevents us from having to
    share a common enum with the compiler.  */
@@ -2289,9 +2327,7 @@ formatted_transfer (st_parameter_dt *dtp, bt type,
 void
 transfer_integer (st_parameter_dt *dtp, void *p, int kind)
 {
-  if ((dtp->common.flags & IOPARM_LIBRETURN_MASK) != IOPARM_LIBRETURN_OK)
-    return;
-  dtp->u.p.transfer (dtp, BT_INTEGER, p, kind, kind, 1);
+    wrap_scalar_transfer (dtp, BT_INTEGER, p, kind, kind, 1);
 }
 
 void
@@ -2307,7 +2343,7 @@ transfer_real (st_parameter_dt *dtp, void *p, int
   if ((dtp->common.flags & IOPARM_LIBRETURN_MASK) != IOPARM_LIBRETURN_OK)
     return;
   size = size_from_real_kind (kind);
-  dtp->u.p.transfer (dtp, BT_REAL, p, kind, size, 1);
+  wrap_scalar_transfer(dtp, BT_REAL, p, kind, size, 1);
 }
 
 void
@@ -2319,9 +2355,7 @@ transfer_real_write (st_parameter_dt *dtp, void *p
 void
 transfer_logical (st_parameter_dt *dtp, void *p, int kind)
 {
-  if ((dtp->common.flags & IOPARM_LIBRETURN_MASK) != IOPARM_LIBRETURN_OK)
-    return;
-  dtp->u.p.transfer (dtp, BT_LOGICAL, p, kind, kind, 1);
+  wrap_scalar_transfer(dtp, BT_LOGICAL, p, kind, kind, 1);
 }
 
 void
@@ -2345,7 +2379,7 @@ transfer_character (st_parameter_dt *dtp, void *p,
     p = empty_string;
 
   /* Set kind here to 1.  */
-  dtp->u.p.transfer (dtp, BT_CHARACTER, p, 1, len, 1);
+  wrap_scalar_transfer(dtp, BT_CHARACTER, p, 1, len, 1);
 }
 
 void
@@ -2369,7 +2403,7 @@ transfer_character_wide (st_parameter_dt *dtp, voi
     p = empty_string;
 
   /* Here we pass the actual kind value.  */
-  dtp->u.p.transfer (dtp, BT_CHARACTER, p, kind, len, 1);
+  wrap_scalar_transfer(dtp, BT_CHARACTER, p, kind, len, 1);
 }
 
 void
@@ -2385,7 +2419,7 @@ transfer_complex (st_parameter_dt *dtp, void *p, i
   if ((dtp->common.flags & IOPARM_LIBRETURN_MASK) != IOPARM_LIBRETURN_OK)
     return;
   size = size_from_complex_kind (kind);
-  dtp->u.p.transfer (dtp, BT_COMPLEX, p, kind, size, 1);
+  wrap_scalar_transfer(dtp, BT_COMPLEX, p, kind, size, 1);
 }
 
 void
@@ -2395,8 +2429,8 @@ transfer_complex_write (st_parameter_dt *dtp, void
 }
 
 void
-transfer_array (st_parameter_dt *dtp, gfc_array_char *desc, int kind,
-		gfc_charlen_type charlen)
+transfer_array_inner (st_parameter_dt *dtp, gfc_array_char *desc, int kind,
+		      gfc_charlen_type charlen)
 {
   index_type count[GFC_MAX_DIMENSIONS];
   index_type extent[GFC_MAX_DIMENSIONS];
@@ -2471,6 +2505,34 @@ void
 }
 
 void
+transfer_array (st_parameter_dt *dtp, gfc_array_char *desc, int kind,
+	        gfc_charlen_type charlen)
+{
+  if ((dtp->common.flags & IOPARM_LIBRETURN_MASK) != IOPARM_LIBRETURN_OK)
+    return;
+
+  if (dtp->u.p.current_unit && dtp->u.p.current_unit->au)
+    {
+      if (dtp->u.p.async)
+	{
+	  transfer_args args;
+	  size_t sz = sizeof (gfc_array_char)
+	              + sizeof (descriptor_dimension) * GFC_DESCRIPTOR_RANK (desc);
+	  args.array.desc = xmalloc (sz);
+	  NOTE("desc = %p", (void *) args.array.desc);
+	  memcpy (args.array.desc, desc, sz);
+	  args.array.kind = kind; 
+	  args.array.charlen = charlen;
+	  enqueue_transfer(dtp->u.p.current_unit->au, &args, AIO_TRANSFER_ARRAY);
+	  return;
+	}
+    }
+  /* Come here if there was no asynchronous I/O to be scheduled.  */
+  transfer_array_inner (dtp, desc, kind, charlen);
+}
+
+
+void
 transfer_array_write (st_parameter_dt *dtp, gfc_array_char *desc, int kind,
 		      gfc_charlen_type charlen)
 {
@@ -2492,7 +2554,7 @@ transfer_derived (st_parameter_dt *parent, void *d
       else
 	parent->u.p.fdtio_ptr = (formatted_dtio) dtio_proc;
     }
-  parent->u.p.transfer (parent, BT_CLASS, dtio_source, 0, 0, 1);
+  wrap_scalar_transfer(parent, BT_CLASS, dtio_source, 0, 0, 1);
 }
 
 
@@ -2770,6 +2832,29 @@ data_transfer_init (st_parameter_dt *dtp, int read
   else if (dtp->u.p.current_unit->internal_unit_kind > 0)
     dtp->u.p.unit_is_internal = 1;
 
+  if ((cf & IOPARM_DT_HAS_ASYNCHRONOUS) != 0)
+    {
+      int f;
+      f = find_option (&dtp->common, dtp->asynchronous, dtp->asynchronous_len,
+		       async_opt, "Bad ASYNCHRONOUS in data transfer statement");
+      if (f == ASYNC_YES && dtp->u.p.current_unit->flags.async != ASYNC_YES)
+	{
+	  generate_error (&dtp->common, LIBERROR_OPTION_CONFLICT,
+			  "ASYNCHRONOUS transfer without ASYHCRONOUS='YES' in OPEN");
+	  return;
+	}
+      dtp->u.p.async = f == ASYNC_YES;
+    }
+
+  /* Perform a wait operation for any pending asynchronous I/O.  This needs to
+     be done before all other error checks. See F2008, 9.6.4.1.  */
+  
+  if (dtp->u.p.current_unit->au && !dtp->u.p.async)
+    {
+      if (async_wait (&(dtp->common), dtp->u.p.current_unit->au))
+	return;
+    }
+
   /* Check the action.  */
 
   if (read_flag && dtp->u.p.current_unit->flags.action == ACTION_WRITE)
@@ -3184,6 +3269,9 @@ data_transfer_init (st_parameter_dt *dtp, int read
 	dtp->u.p.current_unit->read_bad = 1;
     }
 
+  if (dtp->u.p.current_unit->au)
+    change_pdt(dtp->u.p.current_unit->au, dtp); 
+
   if (dtp->u.p.current_unit->flags.form == FORM_FORMATTED)
     {
 #ifdef HAVE_USELOCALE
@@ -4099,7 +4187,7 @@ extern void st_read_done (st_parameter_dt *);
 export_proto(st_read_done);
 
 void
-st_read_done (st_parameter_dt *dtp)
+st_read_done_worker (st_parameter_dt *dtp)
 {
   finalize_transfer (dtp);
 
@@ -4127,6 +4215,24 @@ void
 	  free_format_data (dtp->u.p.fmt);
 	  free_format (dtp);
 	}
+    }
+}
+
+void
+st_read_done(st_parameter_dt *dtp) 
+{
+  if (dtp->u.p.current_unit)
+    {
+      if (dtp->u.p.current_unit->au)
+	{
+	  if (dtp->common.flags & IOPARM_DT_HAS_ID)
+	    *dtp->id = enqueue_done_id (dtp->u.p.current_unit->au, AIO_READ_DONE);
+	  else
+	    enqueue_done (dtp->u.p.current_unit->au, AIO_READ_DONE);
+	}
+      else
+	st_read_done_worker (dtp);
+  
       unlock_unit (dtp->u.p.current_unit);
     }
 
@@ -4143,11 +4249,9 @@ st_write (st_parameter_dt *dtp)
   data_transfer_init (dtp, 0);
 }
 
-extern void st_write_done (st_parameter_dt *);
-export_proto(st_write_done);
 
 void
-st_write_done (st_parameter_dt *dtp)
+st_write_done_worker (st_parameter_dt *dtp)
 {
   finalize_transfer (dtp);
 
@@ -4196,19 +4300,61 @@ void
 	  free_format_data (dtp->u.p.fmt);
 	  free_format (dtp);
 	}
+    }
+}
+
+extern void st_write_done (st_parameter_dt *);
+export_proto(st_write_done);
+
+void
+st_write_done (st_parameter_dt *dtp)
+{
+  if (dtp->u.p.current_unit)
+    {
+      if (dtp->u.p.current_unit->au)
+	{
+	  if (dtp->common.flags & IOPARM_DT_HAS_ID)
+	    *dtp->id = enqueue_done_id(dtp->u.p.current_unit->au, AIO_WRITE_DONE);
+	  else
+	    enqueue_done (dtp->u.p.current_unit->au, AIO_WRITE_DONE);
+	}
+      else
+	st_write_done_worker (dtp);
+
       unlock_unit (dtp->u.p.current_unit);
     }
+
   library_end ();
 }
 
+/* Wait operation.  We need to keep around the do-nothing version
+ of st_wait for compatibility with previous versions, which had marked
+ the argument as unused (and thus liable to be removed).
 
-/* F2003: This is a stub for the runtime portion of the WAIT statement.  */
+ TODO: remove at next bump in version number.  */
+
 void
 st_wait (st_parameter_wait *wtp __attribute__((unused)))
 {
+  return;
 }
 
+void
+st_wait_async (st_parameter_wait *wtp)
+{
+  gfc_unit *u = find_unit(wtp->common.unit);
+  if (u->au)
+    {
+      if (wtp->common.flags & IOPARM_WAIT_HAS_ID) 
+	async_wait_id (&(wtp->common), u->au, *wtp->id);
+      else
+	async_wait (&(wtp->common), u->au);
+    }
 
+  unlock_unit(u); 
+}
+
+
 /* Receives the scalar information for namelist objects and stores it
    in a linked list of namelist_info types.  */
 
Index: libgfortran/io/unit.c
===================================================================
--- libgfortran/io/unit.c	(Revision 259739)
+++ libgfortran/io/unit.c	(Arbeitskopie)
@@ -27,6 +27,7 @@ see the files COPYING3 and COPYING.RUNTIME respect
 #include "fbuf.h"
 #include "format.h"
 #include "unix.h"
+#include "async.h"
 #include <string.h>
 #include <assert.h>
 
@@ -240,7 +241,7 @@ insert_unit (int n)
 #else
   __GTHREAD_MUTEX_INIT_FUNCTION (&u->lock);
 #endif
-  __gthread_mutex_lock (&u->lock);
+  LOCK (&u->lock);
   u->priority = pseudo_random ();
   unit_root = insert (u, unit_root);
   return u;
@@ -327,7 +328,9 @@ get_gfc_unit (int n, int do_create)
   gfc_unit *p;
   int c, created = 0;
 
-  __gthread_mutex_lock (&unit_lock);
+  NOTE("Unit n=%d, do_create = %d", n, do_create);
+  LOCK(&unit_lock);
+
 retry:
   for (c = 0; c < CACHE_SIZE; c++)
     if (unit_cache[c] != NULL && unit_cache[c]->unit_number == n)
@@ -366,7 +369,7 @@ retry:
     {
       /* Newly created units have their lock held already
 	 from insert_unit.  Just unlock UNIT_LOCK and return.  */
-      __gthread_mutex_unlock (&unit_lock);
+      UNLOCK(&unit_lock);
       return p;
     }
 
@@ -374,10 +377,10 @@ found:
   if (p != NULL && (p->child_dtio == 0))
     {
       /* Fast path.  */
-      if (! __gthread_mutex_trylock (&p->lock))
+      if (! TRYLOCK (&p->lock))
 	{
 	  /* assert (p->closed == 0); */
-	  __gthread_mutex_unlock (&unit_lock);
+	  UNLOCK(&unit_lock);
 	  return p;
 	}
 
@@ -385,15 +388,15 @@ found:
     }
 
 
-  __gthread_mutex_unlock (&unit_lock);
+  UNLOCK (&unit_lock);
 
   if (p != NULL && (p->child_dtio == 0))
     {
-      __gthread_mutex_lock (&p->lock);
+      LOCK (&p->lock);
       if (p->closed)
 	{
-	  __gthread_mutex_lock (&unit_lock);
-	  __gthread_mutex_unlock (&p->lock);
+	  LOCK (&unit_lock);
+	  UNLOCK (&p->lock);
 	  if (predec_waiting_locked (p) == 0)
 	    destroy_unit_mutex (p);
 	  goto retry;
@@ -640,7 +643,7 @@ init_units (void)
 
       fbuf_init (u, 0);
 
-      __gthread_mutex_unlock (&u->lock);
+      UNLOCK (&u->lock);
     }
 
   if (options.stdout_unit >= 0)
@@ -671,7 +674,7 @@ init_units (void)
 
       fbuf_init (u, 0);
 
-      __gthread_mutex_unlock (&u->lock);
+      UNLOCK (&u->lock);
     }
 
   if (options.stderr_unit >= 0)
@@ -702,13 +705,13 @@ init_units (void)
       fbuf_init (u, 256);  /* 256 bytes should be enough, probably not doing
                               any kind of exotic formatting to stderr.  */
 
-      __gthread_mutex_unlock (&u->lock);
+      UNLOCK (&u->lock);
     }
   /* The default internal units.  */
   u = insert_unit (GFC_INTERNAL_UNIT);
-  __gthread_mutex_unlock (&u->lock);
+  UNLOCK (&u->lock);
   u = insert_unit (GFC_INTERNAL_UNIT4);
-  __gthread_mutex_unlock (&u->lock);
+  UNLOCK (&u->lock);
 }
 
 
@@ -717,6 +720,9 @@ close_unit_1 (gfc_unit *u, int locked)
 {
   int i, rc;
 
+  if(u->au)
+    async_close (u->au);
+
   /* If there are previously written bytes from a write with ADVANCE="no"
      Reposition the buffer before closing.  */
   if (u->previous_nonadvancing_write)
@@ -723,10 +729,10 @@ close_unit_1 (gfc_unit *u, int locked)
     finish_last_advance_record (u);
 
   rc = (u->s == NULL) ? 0 : sclose (u->s) == -1;
-
+  
   u->closed = 1;
   if (!locked)
-    __gthread_mutex_lock (&unit_lock);
+    LOCK (&unit_lock);
 
   for (i = 0; i < CACHE_SIZE; i++)
     if (unit_cache[i] == u)
@@ -744,7 +750,7 @@ close_unit_1 (gfc_unit *u, int locked)
     newunit_free (u->unit_number);
 
   if (!locked)
-    __gthread_mutex_unlock (&u->lock);
+    UNLOCK (&u->lock);
 
   /* If there are any threads waiting in find_unit for this unit,
      avoid freeing the memory, the last such thread will free it
@@ -753,7 +759,7 @@ close_unit_1 (gfc_unit *u, int locked)
     destroy_unit_mutex (u);
 
   if (!locked)
-    __gthread_mutex_unlock (&unit_lock);
+    UNLOCK (&unit_lock);
 
   return rc;
 }
@@ -761,7 +767,9 @@ close_unit_1 (gfc_unit *u, int locked)
 void
 unlock_unit (gfc_unit *u)
 {
-  __gthread_mutex_unlock (&u->lock);
+  NOTE ("unlock_unit = %d", u->unit_number);
+  UNLOCK (&u->lock);
+  NOTE ("unlock_unit done");
 }
 
 /* close_unit()-- Close a unit.  The stream is closed, and any memory
@@ -785,10 +793,10 @@ close_unit (gfc_unit *u)
 void
 close_units (void)
 {
-  __gthread_mutex_lock (&unit_lock);
+  LOCK (&unit_lock);
   while (unit_root != NULL)
     close_unit_1 (unit_root, 1);
-  __gthread_mutex_unlock (&unit_lock);
+  UNLOCK (&unit_lock);
 
   free (newunits);
 
@@ -895,7 +903,7 @@ finish_last_advance_record (gfc_unit *u)
 int
 newunit_alloc (void)
 {
-  __gthread_mutex_lock (&unit_lock);
+  LOCK (&unit_lock);
   if (!newunits)
     {
       newunits = xcalloc (16, 1);
@@ -909,7 +917,7 @@ newunit_alloc (void)
         {
           newunits[ii] = true;
           newunit_lwi = ii + 1;
-	  __gthread_mutex_unlock (&unit_lock);
+	  UNLOCK (&unit_lock);
           return -ii + NEWUNIT_START;
         }
     }
@@ -922,7 +930,7 @@ newunit_alloc (void)
   memset (newunits + old_size, 0, old_size);
   newunits[old_size] = true;
   newunit_lwi = old_size + 1;
-    __gthread_mutex_unlock (&unit_lock);
+    UNLOCK (&unit_lock);
   return -old_size + NEWUNIT_START;
 }
 
Index: libgfortran/io/unix.c
===================================================================
--- libgfortran/io/unix.c	(Revision 259739)
+++ libgfortran/io/unix.c	(Arbeitskopie)
@@ -27,6 +27,7 @@ see the files COPYING3 and COPYING.RUNTIME respect
 
 #include "io.h"
 #include "unix.h"
+#include "async.h"
 #include <limits.h>
 
 #ifdef HAVE_UNISTD_H
@@ -1742,7 +1743,7 @@ find_file (const char *file, gfc_charlen_type file
   id = id_from_path (path);
 #endif
 
-  __gthread_mutex_lock (&unit_lock);
+  LOCK (&unit_lock);
 retry:
   u = find_file0 (unit_root, FIND_FILE0_ARGS);
   if (u != NULL)
@@ -1751,20 +1752,20 @@ retry:
       if (! __gthread_mutex_trylock (&u->lock))
 	{
 	  /* assert (u->closed == 0); */
-	  __gthread_mutex_unlock (&unit_lock);
+	  UNLOCK (&unit_lock);
 	  goto done;
 	}
 
       inc_waiting_locked (u);
     }
-  __gthread_mutex_unlock (&unit_lock);
+  UNLOCK (&unit_lock);
   if (u != NULL)
     {
-      __gthread_mutex_lock (&u->lock);
+      LOCK (&u->lock);
       if (u->closed)
 	{
-	  __gthread_mutex_lock (&unit_lock);
-	  __gthread_mutex_unlock (&u->lock);
+	  LOCK (&unit_lock);
+	  UNLOCK (&u->lock);
 	  if (predec_waiting_locked (u) == 0)
 	    free (u);
 	  goto retry;
@@ -1794,7 +1795,7 @@ flush_all_units_1 (gfc_unit *u, int min_unit)
 	    return u;
 	  if (u->s)
 	    sflush (u->s);
-	  __gthread_mutex_unlock (&u->lock);
+	  UNLOCK (&u->lock);
 	}
       u = u->right;
     }
@@ -1807,17 +1808,17 @@ flush_all_units (void)
   gfc_unit *u;
   int min_unit = 0;
 
-  __gthread_mutex_lock (&unit_lock);
+  LOCK (&unit_lock);
   do
     {
       u = flush_all_units_1 (unit_root, min_unit);
       if (u != NULL)
 	inc_waiting_locked (u);
-      __gthread_mutex_unlock (&unit_lock);
+      UNLOCK (&unit_lock);
       if (u == NULL)
 	return;
 
-      __gthread_mutex_lock (&u->lock);
+      LOCK (&u->lock);
 
       min_unit = u->unit_number + 1;
 
@@ -1824,14 +1825,14 @@ flush_all_units (void)
       if (u->closed == 0)
 	{
 	  sflush (u->s);
-	  __gthread_mutex_lock (&unit_lock);
-	  __gthread_mutex_unlock (&u->lock);
+	  LOCK (&unit_lock);
+	  UNLOCK (&u->lock);
 	  (void) predec_waiting_locked (u);
 	}
       else
 	{
-	  __gthread_mutex_lock (&unit_lock);
-	  __gthread_mutex_unlock (&u->lock);
+	  LOCK (&unit_lock);
+	  UNLOCK (&u->lock);
 	  if (predec_waiting_locked (u) == 0)
 	    free (u);
 	}
Index: libgfortran/libgfortran.h
===================================================================
--- libgfortran/libgfortran.h	(Revision 259739)
+++ libgfortran/libgfortran.h	(Arbeitskopie)
@@ -743,6 +743,9 @@ internal_proto(translate_error);
 extern void generate_error (st_parameter_common *, int, const char *);
 iexport_proto(generate_error);
 
+extern bool generate_error_common (st_parameter_common *, int, const char *);
+iexport_proto(generate_error_common);
+
 extern void generate_warning (st_parameter_common *, const char *);
 internal_proto(generate_warning);
 
@@ -1748,5 +1751,7 @@ void cshift1_16_c16 (gfc_array_c16 * const restric
 internal_proto(cshift1_16_c16);
 #endif
 
+/* Define this if we support asynchronous I/O on this platform.  This
+   currently requires weak symbols.  */
 
 #endif  /* LIBGFOR_H  */
Index: libgfortran/runtime/error.c
===================================================================
--- libgfortran/runtime/error.c	(Revision 259739)
+++ libgfortran/runtime/error.c	(Arbeitskopie)
@@ -24,6 +24,9 @@ see the files COPYING3 and COPYING.RUNTIME respect
 
 
 #include "libgfortran.h"
+#include "io.h"
+#include "async.h"
+
 #include <assert.h>
 #include <string.h>
 #include <errno.h>
@@ -526,24 +529,30 @@ translate_error (int code)
 }
 
 
-/* generate_error()-- Come here when an error happens.  This
- * subroutine is called if it is possible to continue on after the error.
- * If an IOSTAT or IOMSG variable exists, we set it.  If IOSTAT or
- * ERR labels are present, we return, otherwise we terminate the program
- * after printing a message.  The error code is always required but the
- * message parameter can be NULL, in which case a string describing
- * the most recent operating system error is used. */
+/* Worker function for generate_error and generate_error_async.  Return true
+   if a straight return is to be done, zero if the program should abort. */
 
-void
-generate_error (st_parameter_common *cmp, int family, const char *message)
+bool
+generate_error_common (st_parameter_common *cmp, int family, const char *message)
 {
   char errmsg[STRERR_MAXSZ];
+  gfc_unit *u;
 
+  u = thread_unit;
+  if (u && u->au && __gthread_equal (u->au->thread, __gthread_self ()))
+    {
+      u->au->error.has_error = 1;
+      u->au->error.cmp = cmp;
+      u->au->error.family = family;
+      u->au->error.message = message;
+      return true;
+    }
+
   /* If there was a previous error, don't mask it with another
      error message, EOF or EOR condition.  */
 
   if ((cmp->flags & IOPARM_LIBRETURN_MASK) == IOPARM_LIBRETURN_ERROR)
-    return;
+    return true;
 
   /* Set the error status.  */
   if ((cmp->flags & IOPARM_HAS_IOSTAT))
@@ -564,27 +573,28 @@ translate_error (int code)
     case LIBERROR_EOR:
       cmp->flags |= IOPARM_LIBRETURN_EOR;
       if ((cmp->flags & IOPARM_EOR))
-	return;
+	return true;
       break;
 
     case LIBERROR_END:
       cmp->flags |= IOPARM_LIBRETURN_END;
       if ((cmp->flags & IOPARM_END))
-	return;
+	return true;
       break;
 
     default:
       cmp->flags |= IOPARM_LIBRETURN_ERROR;
       if ((cmp->flags & IOPARM_ERR))
-	return;
+	return true;
       break;
     }
 
   /* Return if the user supplied an iostat variable.  */
   if ((cmp->flags & IOPARM_HAS_IOSTAT))
-    return;
+    return true;
 
-  /* Terminate the program */
+  /* Return code, caller is responsible for terminating
+   the program if necessary.  */
 
   recursion_check ();
   show_locus (cmp);
@@ -591,8 +601,27 @@ translate_error (int code)
   estr_write ("Fortran runtime error: ");
   estr_write (message);
   estr_write ("\n");
-  exit_error (2);
+  return false;
 }
+
+/* generate_error()-- Come here when an error happens.  This
+ * subroutine is called if it is possible to continue on after the error.
+ * If an IOSTAT or IOMSG variable exists, we set it.  If IOSTAT or
+ * ERR labels are present, we return, otherwise we terminate the program
+ * after printing a message.  The error code is always required but the
+ * message parameter can be NULL, in which case a string describing
+ * the most recent operating system error is used.
+ * If the error is for an asynchronous unit and if the program is currently
+ * executing the asynchronous thread, just mark the error and return.  */
+
+void
+generate_error (st_parameter_common *cmp, int family, const char *message)
+{
+  if (generate_error_common (cmp, family, message))
+    return;
+
+  exit_error(2);
+}
 iexport(generate_error);