[Ada] Minor: improve comments

2019-12-16  Bob Duff  <duff@adacore.com>

gcc/ada/

	* errout.adb, errout.ads: Improve comments.

From-SVN: r279440

gcc/ada/ChangeLog

 2019-12-16  Bob Duff  <duff@adacore.com>
 
+	* errout.adb, errout.ads: Improve comments.
+
+2019-12-16  Bob Duff  <duff@adacore.com>
+
 	* sem_util.ads: Minor comment fix.
 
 2019-12-16  Bob Duff  <duff@adacore.com>

gcc/ada/errout.adb

@@ -1716,9 +1716,12 @@ package body Errout is
 
    function Is_Size_Too_Small_Message (S : String) return Boolean is
       Size_For : constant String := "size for";
+      pragma Assert (Size_Too_Small_Message (1 .. Size_For'Last) = Size_For);
+      --  Assert that Size_Too_Small_Message starts with Size_For
    begin
       return S'Length >= Size_For'Length
         and then S (S'First .. S'First + Size_For'Length - 1) = Size_For;
+      --  True if S starts with Size_For
    end Is_Size_Too_Small_Message;
 
    -----------------

gcc/ada/errout.ads

@@ -957,8 +957,9 @@ package Errout is
    function Is_Size_Too_Small_Message (S : String) return Boolean;
    Size_Too_Small_Message : constant String :=
      "size for& too small, minimum allowed is ^";
-   --  This message is explicitly tested in Special_Msg_Delete in the package
-   --  body, which is somewhat questionable, but at least by using a constant
-   --  we are obeying the DRY principle.
+   --  This message is printed in Freeze and Sem_Ch13. We also test for it in
+   --  the body of this package (see Special_Msg_Delete) ???which is somewhat
+   --  questionable. The Is_Size_Too_Small_Message function tests for it by
+   --  testing a prefix. The function and constant should be kept in synch.
 
 end Errout;