The 'Size of a discrete subtype with a null range should be zero. The
following test:
1. with Ada.Text_IO; use Ada.Text_IO;
2. procedure Static_Null_Range_Size is
3. subtype Static_Null_Range is
4. Integer range 5 .. 0;
5. Dummy : Static_Null_Range;
6. begin
7. Put_Line ("Static_Null_Range:");
8. Put_Line (" Type'Size is " &
9. Natural'Image
10. (Static_Null_Range'Size));
11. Put_Line (" Object'Size is " &
12. Natural'Image (Dummy'Size));
13. if Static_Null_Range'Size /= 0 then
14. raise Program_Error;
15. end if;
16. end Static_Null_Range_Size;
should generate the output:
Static_Null_Range:
Type'Size is 0
Object'Size is 32
and not raise an exception.
Tested on x86_64-pc-linux-gnu, committed on trunk
2015-05-22 Robert Dewar <de...@adacore.com>
* sem_ch13.adb (Minimum_Size): Size is zero for null range
discrete subtype.
Index: sem_ch13.adb
===================================================================
--- sem_ch13.adb (revision 223555)
+++ sem_ch13.adb (working copy)
@@ -11718,11 +11718,20 @@
Lo := Uint_0;
end if;
+ -- Null range case, size is always zero. We only do this in the discrete
+ -- type case, since that's the odd case that came up. Probably we should
+ -- also do this in the fixed-point case, but doing so causes peculiar
+ -- gigi failures, and it is not worth worrying about this incredibly
+ -- marginal case (explicit null-range fixed-point type declarations)???
+
+ if Lo > Hi and then Is_Discrete_Type (T) then
+ S := 0;
+
-- Signed case. Note that we consider types like range 1 .. -1 to be
-- signed for the purpose of computing the size, since the bounds have
-- to be accommodated in the base type.
- if Lo < 0 or else Hi < 0 then
+ elsif Lo < 0 or else Hi < 0 then
S := 1;
B := Uint_1;
