[Ada] Define default value for Process field

2019-10-10  Vadim Godunko  <godunko@adacore.com>

gcc/ada/

	* libgnat/g-exptty.ads (TTY_Process_Descriptor): Set default
	value for Process.

From-SVN: r276820

gcc/ada/ChangeLog

-2019-10-10  Bob Duff  <duff@adacore.com>
+2019-10-10  Vadim Godunko  <godunko@adacore.com>
 
-	* sem_prag.adb (Defer_Compile_Time_Warning_Error_To_BE): In
-	addition to saving the pragma for further processing, copy the
-	pragma into the main unit if necessary.
\ No newline at end of file
+	* libgnat/g-exptty.ads (TTY_Process_Descriptor): Set default
+	value for Process.
\ No newline at end of file

gcc/ada/libgnat/g-exptty.ads

@@ -139,7 +139,7 @@ private
    Still_Active : constant Integer := -1;
 
    type TTY_Process_Descriptor is new Process_Descriptor with record
-      Process     : System.Address;
+      Process     : System.Address := System.Null_Address;
       --  Underlying structure used in C
       Exit_Status : Integer := Still_Active;
       --  Hold the exit status of the process.