When issuing a warning on a read of an uninitialized variable through
reading an attribute such as Loop_Entry, GNAT could crash. Now fixed.
GNAT issues a warning as expected on the following code:
$ gcc -c s.adb
1. package S is
2.
3. type Array_Range is range 1 .. 10;
4.
5. type IntArray is array (Array_Range) of Integer;
6.
7. procedure Move (Dest, Src : aliased out IntArray);
8.
9. end S;
1. package body S is
2.
3. procedure Move (Dest, Src : aliased out IntArray) is
4. begin
5. for Index in Dest'Range loop
6. pragma Assert (for all J in Dest'First .. Index - 1 =>
7. Dest (J) = Src'Loop_Entry (J));
1 2
>>> warning: "Dest" may be referenced before it has a value
>>> warning: "Src" may be referenced before it has a value
8.
9. Dest (Index) := Src (Index);
10. Src (Index) := 0;
11. end loop;
12. end Move;
13.
14. end S;
Tested on x86_64-pc-linux-gnu, committed on trunk
2017-09-06 Yannick Moy <m...@adacore.com>
* sem_warn.adb (Check_References): Take into
account possibility of attribute reference as original node.
Index: sem_warn.adb
===================================================================
--- sem_warn.adb (revision 251773)
+++ sem_warn.adb (working copy)
@@ -1382,16 +1382,22 @@
-- deal with case where original unset reference has been
-- rewritten during expansion.
- -- In some cases, the original node may be a type conversion
- -- or qualification, and in this case we want the object
- -- entity inside.
+ -- In some cases, the original node may be a type
+ -- conversion, a qualification or an attribute reference and
+ -- in this case we want the object entity inside. Same for
+ -- an expression with actions.
UR := Original_Node (UR);
while Nkind (UR) = N_Type_Conversion
or else Nkind (UR) = N_Qualified_Expression
or else Nkind (UR) = N_Expression_With_Actions
+ or else Nkind (UR) = N_Attribute_Reference
loop
- UR := Expression (UR);
+ if Nkind (UR) = N_Attribute_Reference then
+ UR := Prefix (UR);
+ else
+ UR := Expression (UR);
+ end if;
end loop;
-- Don't issue warning if appearing inside Initial_Condition
