* linux-thread-db.c (set_libthread_db_search_path): New function.

(_initialize_thread_db): Add setter for libthread-db-search-path.

	gdbserver/
	* thread-db.c (thread_db_handle_monitor_command): Handle elided path.

	doc/
	* gdb.texinfo (Threads): If an empty path is provided for
	libthread-db-search-path it is reset to its default value.
	(Server): Ditto.

gdb/ChangeLog

@@ -1,3 +1,8 @@
+2011-05-10  Doug Evans  <dje@google.com>
+
+	* linux-thread-db.c (set_libthread_db_search_path): New function.
+	(_initialize_thread_db): Add setter for libthread-db-search-path.
+
 2011-05-09  Doug Evans  <dje@google.com>
 
 	* NEWS: Mention --with-iconv-bin.

gdb/doc/ChangeLog

@@ -1,3 +1,9 @@
+2011-05-10  Doug Evans  <dje@google.com>
+
+	* gdb.texinfo (Threads): If an empty path is provided for
+	libthread-db-search-path it is reset to its default value.
+	(Server): Ditto.
+
 2011-05-09  Doug Evans  <dje@google.com>
 
 	* gdb.texinfo (Requirements): Fix typo.  Mention --with-iconv-bin.

gdb/doc/gdb.texinfo

@@ -2855,7 +2855,7 @@ watchpoints in programs with multiple threads.
 If this variable is set, @var{path} is a colon-separated list of
 directories @value{GDBN} will use to search for @code{libthread_db}.
 If you omit @var{path}, @samp{libthread-db-search-path} will be reset to
-an empty list.
+its default value.
 
 On @sc{gnu}/Linux and Solaris systems, @value{GDBN} uses a ``helper''
 @code{libthread_db} library to obtain information about threads in the
@@ -16369,7 +16369,7 @@ protocol (@pxref{Remote Protocol}).
 When this command is issued, @var{path} is a colon-separated list of
 directories to search for @code{libthread_db} (@pxref{Threads,,set
 libthread-db-search-path}).  If you omit @var{path},
-@samp{libthread-db-search-path} will be reset to an empty list.
+@samp{libthread-db-search-path} will be reset to its default value.
 
 @item monitor exit
 Tell gdbserver to exit immediately.  This command should be followed by

gdb/gdbserver/ChangeLog

@@ -1,3 +1,7 @@
+2011-05-10  Doug Evans  <dje@google.com>
+
+	* thread-db.c (thread_db_handle_monitor_command): Handle elided path.
+
 2011-05-04  Doug Evans  <dje@google.com>
 
 	* linux-low.c (linux_join): Skip process lookup.

gdb/gdbserver/thread-db.c

@@ -916,9 +916,14 @@ thread_db_mourn (struct process_info *proc)
 int
 thread_db_handle_monitor_command (char *mon)
 {
-  if (strncmp (mon, "set libthread-db-search-path ", 29) == 0)
+  const char *cmd = "set libthread-db-search-path";
+  size_t cmd_len = strlen (cmd);
+
+  if (strncmp (mon, cmd, cmd_len) == 0
+      && (mon[cmd_len] == '\0'
+	  || mon[cmd_len] == ' '))
     {
-      const char *cp = mon + 29;
+      const char *cp = mon + cmd_len;
 
       if (libthread_db_search_path != NULL)
 	free (libthread_db_search_path);
@@ -927,6 +932,8 @@ thread_db_handle_monitor_command (char *mon)
       while (isspace (*cp))
 	++cp;
 
+      if (*cp == '\0')
+	cp = LIBTHREAD_DB_SEARCH_PATH;
       libthread_db_search_path = xstrdup (cp);
 
       monitor_output ("libthread-db-search-path set to `");

gdb/linux-thread-db.c

@@ -75,6 +75,17 @@
 
 static char *libthread_db_search_path;
 
+static void
+set_libthread_db_search_path (char *ignored, int from_tty,
+			      struct cmd_list_element *c)
+{
+  if (*libthread_db_search_path == '\0')
+    {
+      xfree (libthread_db_search_path);
+      libthread_db_search_path = xstrdup (LIBTHREAD_DB_SEARCH_PATH);
+    }
+}
+
 /* If non-zero, print details of libthread_db processing.  */
 
 static int libthread_db_debug;
@@ -1719,8 +1730,10 @@ _initialize_thread_db (void)
 Set search path for libthread_db."), _("\
 Show the current search path or libthread_db."), _("\
 This path is used to search for libthread_db to be loaded into \
-gdb itself."),
-			    NULL,
+gdb itself.\n\
+Its value is a colon (':') separate list of directories to search.\n\
+Setting the search path to an empty list resets it to its default value."),
+			    set_libthread_db_search_path,
 			    NULL,
 			    &setlist, &showlist);