gdb: try to load libthread_db only after reading all shared libraries when attaching

https://sourceware.org/pipermail/gdb-patches/2021-March/177369.html

---
 gdb/infcmd.c          |  7 ++-----
 gdb/linux-thread-db.c | 24 +++++++++++++++++++-----
 2 files changed, 21 insertions(+), 10 deletions(-)

diff --git a/gdb/infcmd.c b/gdb/infcmd.c
index cfc31699925..345cdc23b0d 100644
--- a/gdb/infcmd.c
+++ b/gdb/infcmd.c
@@ -347,6 +347,8 @@ post_create_inferior (struct target_ops *target, int from_tty)
      if the now pushed target supports hardware watchpoints.  */
   breakpoint_re_set ();
 
+  current_inferior ()->needs_setup = 0;
+
   gdb::observers::inferior_created.notify (target, from_tty);
 }
 
@@ -2414,11 +2416,6 @@ proceed_after_attach (inferior *inf)
 void
 setup_inferior (int from_tty)
 {
-  struct inferior *inferior;
-
-  inferior = current_inferior ();
-  inferior->needs_setup = 0;
-
   /* If no exec file is yet known, try to determine it from the
      process itself.  */
   if (get_exec_file (0) == NULL)
diff --git a/gdb/linux-thread-db.c b/gdb/linux-thread-db.c
index 5498308cf37..61c0237b0e3 100644
--- a/gdb/linux-thread-db.c
+++ b/gdb/linux-thread-db.c
@@ -1010,8 +1010,19 @@ try_thread_db_load (const char *library, bool check_auto_load_safe)
   if (strchr (library, '/') != NULL)
     info->filename = gdb_realpath (library).release ();
 
-  if (try_thread_db_load_1 (info))
-    return true;
+  try
+    {
+      if (try_thread_db_load_1 (info))
+	return true;
+    }
+  catch (const gdb_exception &except)
+    {
+      if (libthread_db_debug)
+	{
+	  exception_fprintf (gdb_stdlog, except,
+			     "Warning: try_thread_db_load: ");
+	}
+    }
 
   /* This library "refused" to work on current inferior.  */
   delete_thread_db_info (current_inferior ()->process_target (),
@@ -1182,10 +1193,13 @@ has_libpthread (void)
 static bool
 thread_db_load (void)
 {
-  struct thread_db_info *info;
+  inferior *inf = current_inferior ();
 
-  info = get_thread_db_info (current_inferior ()->process_target (),
-			     inferior_ptid.pid ());
+  if (inf->needs_setup)
+    return false;
+
+  thread_db_info *info = get_thread_db_info (inf->process_target (),
+					     inferior_ptid.pid ());
 
   if (info != NULL)
     return true;