This patch avoids an overflow on the most-negative number in Output.Write_Int.
No simple test available.
Tested on x86_64-pc-linux-gnu, committed on trunk
2015-10-20 Bob Duff <d...@adacore.com>
* output.adb (Write_Int): Work with negative numbers in order to avoid
negating Int'First and thereby causing overflow.
Index: output.adb
===================================================================
--- output.adb (revision 229023)
+++ output.adb (working copy)
@@ -6,7 +6,7 @@
-- --
-- B o d y --
-- --
--- Copyright (C) 1992-2013, Free Software Foundation, Inc. --
+-- Copyright (C) 1992-2015, Free Software Foundation, Inc. --
-- --
-- GNAT is free software; you can redistribute it and/or modify it under --
-- terms of the GNU General Public License as published by the Free Soft- --
@@ -350,6 +350,7 @@
procedure Write_Char (C : Character) is
begin
+ pragma Assert (Next_Col in Buffer'Range);
if Next_Col = Buffer'Length then
Write_Eol;
end if;
@@ -406,17 +407,29 @@
---------------
procedure Write_Int (Val : Int) is
+ -- Type Int has one extra negative number (i.e. two's complement), so we
+ -- work with negative numbers here. Otherwise, negating Int'First will
+ -- overflow.
+
+ subtype Nonpositive is Int range Int'First .. 0;
+ procedure Write_Abs (Val : Nonpositive);
+ -- Write out the absolute value of Val
+
+ procedure Write_Abs (Val : Nonpositive) is
+ begin
+ if Val < -9 then
+ Write_Abs (Val / 10); -- Recursively write higher digits
+ end if;
+
+ Write_Char (Character'Val (-(Val rem 10) + Character'Pos ('0')));
+ end Write_Abs;
+
begin
if Val < 0 then
Write_Char ('-');
- Write_Int (-Val);
-
+ Write_Abs (Val);
else
- if Val > 9 then
- Write_Int (Val / 10);
- end if;
-
- Write_Char (Character'Val ((Val mod 10) + Character'Pos ('0')));
+ Write_Abs (-Val);
end if;
end Write_Int;
