A reference to an element of a packed array is rewritten through conversions
and masks and shifts. If the prefix of the reference is a source entity we
must generate a reference to it for cross-reference purposes, and to prevent
spurious warnings about unused entities.
Compiling
gcc -c -gnatwa case_2.adb
must yield:
case_2.adb:10:06: warning: unit "System" is not referenced
case_2.adb:37:13: warning: 1 bits of "Storage_Record_Type" unused
--
-- Test case for anomalous GNAT compiler warning.
-- Compile as follows:
-- gnatmake -f -gnatwf case_2
--
-- This will create a warning that the formal parameter "Storage" of the
-- function Test_Function is not referenced, even though it is.
--
with System;
with Text_IO;
procedure Case_2 is
--
-- 32-bit signed integer type
--
type My_Long is range -(2 ** 31) .. +(2 ** 31) - 1;
for My_Long'size use 32;
--
-- Changing this to 64 will prevent the warning from being reported.
--
Record_Size : constant := 65;
--
-- Note: this type is defined as having an extra bit unused for ease of
-- switching the size to 64 to see the warning go away.
-- Even adding an extra field to fill in the unused bit, GNAT still
-- reports the warning.
--
type Storage_Record_Type is
record
E : My_Long;
F : My_Long;
end record with
Size => Record_Size;
type My_Storage_Array_Type is
array (My_Long range <>) of Storage_Record_Type with
Pack => True;
--
-- GNAT gives a warning that "Storage" is not used.
--
function Test_Function
(Storage : in My_Storage_Array_Type;
Left : in My_Long;
Right : in My_Long) return Boolean
is
begin
return Storage (Left).E < Storage (Right).F;
end Test_Function;
--
-- Dummy variables to support the below code.
--
Test : My_Storage_Array_Type (1 .. 1);
Result : Boolean;
begin
--
-- This small bit of code is only here to ensure that none of the above
-- parts get optimized out during compilation.
--
Test (1) := (E => 0, F => 0);
Result := Test_Function (Test, 1, 1);
Text_IO.Put_Line (Boolean'image (Result));
end Case_2;
Tested on x86_64-pc-linux-gnu, committed on trunk
2014-10-23 Ed Schonberg <schonb...@adacore.com>
* exp_pakd.adb (Expand_Packed_Element_Reference): If the
prefix is a source entity, generate a reference to it before
transformation, because rewritten node might not generate a
proper reference, leading to spurious warnings.
Index: exp_pakd.adb
===================================================================
--- exp_pakd.adb (revision 216574)
+++ exp_pakd.adb (working copy)
@@ -30,6 +30,7 @@
with Exp_Dbug; use Exp_Dbug;
with Exp_Util; use Exp_Util;
with Layout; use Layout;
+with Lib.Xref; use Lib.Xref;
with Namet; use Namet;
with Nlists; use Nlists;
with Nmake; use Nmake;
@@ -1682,6 +1683,16 @@
Expand_Packed_Element_Reference (Prefix (N));
end if;
+ -- The prefix may be rewritten below as a conversion. If it is a source
+ -- entity generate reference to it now, to prevent spurious warnings
+ -- about unused entities.
+
+ if Is_Entity_Name (Prefix (N))
+ and then Comes_From_Source (Prefix (N))
+ then
+ Generate_Reference (Entity (Prefix (N)), Prefix (N), 'r');
+ end if;
+
-- If not bit packed, we have the enumeration case, which is easily
-- dealt with (just adjust the subscripts of the indexed component)
