re PR debug/92664 (Wrong .debug_line section information when compiling stdin input with -g3)

	PR debug/92664
	* dwarf2out.c (lookup_filename): Use "<stdin>" instead of "".

From-SVN: r278752

gcc/ChangeLog

+2019-11-27  Jakub Jelinek  <jakub@redhat.com>
+
+	PR debug/92664
+	* dwarf2out.c (lookup_filename): Use "<stdin>" instead of "".
+
 2019-11-26  Martin Sebor  <msebor@redhat.com>
 
 	PR tree-optimization/92683

gcc/dwarf2out.c

@@ -27118,6 +27118,9 @@ lookup_filename (const char *file_name)
   if (!file_name)
     return NULL;
 
+  if (!file_name[0])
+    file_name = "<stdin>";
+
   dwarf_file_data **slot
     = file_table->find_slot_with_hash (file_name, htab_hash_string (file_name),
 				       INSERT);