diff --git a/library/changes b/library/changes
index 2c54e86..c844268 100644
--- a/library/changes
+++ b/library/changes
@@ -130,15 +130,12 @@
   be pulled in only if something references the HUGE_VAL
   constant.
 
-- The thread-safe system() call now blocks all standard I/O operations
-  until the function has returned. Which is harsh, but there is no
-  elegant solution to the issue of keeping the same dos.library
-  file handles from concurrent use which SystemTagList() might just
-  end up using.
-
 - Activated the dormant thread-safe standard input/output/error
   handling code.
 
+- Small fixes to fcntl() and select() to cover the thread-safe
+  fd->fd_DefaultFile == ZERO case.
+
 
 c.lib 1.189 (5.3.2005)
 
diff --git a/library/fcntl_fcntl.c b/library/fcntl_fcntl.c
index a597d49..6e55f31 100644
--- a/library/fcntl_fcntl.c
+++ b/library/fcntl_fcntl.c
@@ -1,5 +1,5 @@
 /*
- * $Id: fcntl_fcntl.c,v 1.13 2005-03-16 09:28:37 obarthel Exp $
+ * $Id: fcntl_fcntl.c,v 1.14 2005-03-25 08:50:59 obarthel Exp $
  *
  * :ts=4
  *
@@ -90,6 +90,12 @@ fcntl(int file_descriptor, int cmd, ... /* int arg */ )
 				goto out;
 			}
 
+			if(fd->fd_DefaultFile == ZERO)
+			{
+				__set_errno(EBADF);
+				goto out;
+			}
+
 			va_start(arg,cmd);
 			l = va_arg(arg,struct flock *);
 			va_end(arg);
@@ -140,6 +146,12 @@ fcntl(int file_descriptor, int cmd, ... /* int arg */ )
 
 			SHOWMSG("cmd=F_SETFL");
 
+			if(fd->fd_DefaultFile == ZERO)
+			{
+				__set_errno(EBADF);
+				goto out;
+			}
+
 			va_start(arg,cmd);
 			flags = va_arg(arg,int);
 			va_end(arg);
diff --git a/library/socket_select.c b/library/socket_select.c
index 38fb37a..f560f57 100644
--- a/library/socket_select.c
+++ b/library/socket_select.c
@@ -1,5 +1,5 @@
 /*
- * $Id: socket_select.c,v 1.8 2005-03-18 12:38:23 obarthel Exp $
+ * $Id: socket_select.c,v 1.9 2005-03-25 08:50:59 obarthel Exp $
  *
  * :ts=4
  *
@@ -309,7 +309,7 @@ map_descriptor_sets(
 			else
 			{
 				/* We only watch files bound to console streams. */
-				if(FLAG_IS_CLEAR(fd->fd_Flags,FDF_IS_INTERACTIVE))
+				if(FLAG_IS_CLEAR(fd->fd_Flags,FDF_IS_INTERACTIVE) || fd->fd_DefaultFile == ZERO)
 				{
 					SHOWMSG("this is a file");
 					continue;
@@ -761,7 +761,7 @@ select(int num_fds,fd_set *read_fds,fd_set *write_fds,fd_set *except_fds,struct
 						{
 							if(FLAG_IS_SET(fd->fd_Flags,FDF_READ))
 							{
-								assert( FLAG_IS_CLEAR(fd->fd_Flags,FDF_IS_SOCKET) );
+								assert( FLAG_IS_CLEAR(fd->fd_Flags,FDF_IS_SOCKET) && fd->fd_DefaultFile != ZERO );
 
 								/* Does this one have input? */
 								PROFILE_OFF();
@@ -921,7 +921,7 @@ select(int num_fds,fd_set *read_fds,fd_set *write_fds,fd_set *except_fds,struct
 						{
 							if(FLAG_IS_SET(fd->fd_Flags,FDF_READ))
 							{
-								assert( FLAG_IS_CLEAR(fd->fd_Flags,FDF_IS_SOCKET) );
+								assert( FLAG_IS_CLEAR(fd->fd_Flags,FDF_IS_SOCKET) && fd->fd_DefaultFile != ZERO );
 
 								PROFILE_OFF();
 
diff --git a/library/stdlib_constructor_begin.c b/library/stdlib_constructor_begin.c
index cf10f06..a63e60c 100644
--- a/library/stdlib_constructor_begin.c
+++ b/library/stdlib_constructor_begin.c
@@ -1,5 +1,5 @@
 /*
- * $Id: stdlib_constructor_begin.c,v 1.9 2005-03-20 12:14:09 obarthel Exp $
+ * $Id: stdlib_constructor_begin.c,v 1.10 2005-03-25 08:50:59 obarthel Exp $
  *
  * :ts=4
  *
@@ -52,7 +52,12 @@ extern void	(* __far __dtors[])(void);
 
 /* With SAS/C this function is placed in front of the first constructor
    table entry. It will invoke all following constructors and
-   finally all the destructors. We don't use this approach here. */
+   finally all the destructors. We don't use this approach here and
+   we can't because the naming scheme we use for the constructor and
+   destructor functions differs from the default SAS/C usage. With
+   SAS/C the default behaviour is to invoke the constructors in
+   ascending order of priority. We invoke them in descending order of
+   priority (highest first). */
 void
 __construct(void)
 {
@@ -71,6 +76,7 @@ _init(void)
 		int num_constructors;
 		int i;
 
+		/* Count the number of constructors we have to deal with. */
 		num_constructors = 0;
 
 		while(__ctors[num_constructors] != NULL)
@@ -98,6 +104,7 @@ _fini(void)
 
 		int num_destructors;
 
+		/* Count the number of destructors we have to deal with. */
 		num_destructors = 0;
 
 		while(__dtors[num_destructors] != NULL)
diff --git a/library/stdlib_system.c b/library/stdlib_system.c
index a73ad05..344a98b 100644
--- a/library/stdlib_system.c
+++ b/library/stdlib_system.c
@@ -1,5 +1,5 @@
 /*
- * $Id: stdlib_system.c,v 1.6 2005-03-24 15:31:16 obarthel Exp $
+ * $Id: stdlib_system.c,v 1.7 2005-03-25 08:50:59 obarthel Exp $
  *
  * :ts=4
  *
@@ -177,17 +177,13 @@ system(const char * command)
 
 		PROFILE_OFF();
 
-		/* In thread-safe mode, system() operation can interfere with
-		   regular file I/O if the same dos.library file handles are
-		   involved. Because we really cannot predict which file handles
-		   will be associated with the current Output() and Input()
-		   streams, we play it safe and just block everything. */
-		__stdio_lock();
+		/* Push all currently buffered output towards the file handles,
+		   in case the program to be launched writes to these files
+		   or the console, too. */
+		__flush_all_files(-1);
 
 		result = SystemTagList((STRPTR)command, (struct TagItem *)system_tags);
 
-		__stdio_unlock();
-
 		PROFILE_ON();
 	}