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Fix uniqueness of address for aliased objects

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Two aliased objects must have distinct addresses, even if they have
size zero, so we make sure to allocate at least one byte for them.

	* gcc-interface/decl.c (gnat_to_gnu_entity) <E_Variable>: Force at
	least the unit size for an aliased object of a constrained nominal
	subtype whose size is variable.
This commit is contained in:
Eric Botcazou 2020-05-08 17:18:20 +02:00
parent bb1ec4773a
commit e34495985e
4 changed files with 41 additions and 3 deletions
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6
gcc/ada/ChangeLog
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@ -1,3 +1,9 @@
2020-05-08 Eric Botcazou <ebotcazou@adacore.com>
* gcc-interface/decl.c (gnat_to_gnu_entity) <E_Variable>: Force at
least the unit size for an aliased object of a constrained nominal
subtype whose size is variable.
2020-05-08 Eric Botcazou <ebotcazou@adacore.com>
* gcc-interface/decl.c (gnat_to_gnu_entity) <E_Array_Subtype>: Deal

15
gcc/ada/gcc-interface/decl.c
View file

@ -969,10 +969,19 @@ gnat_to_gnu_entity (Entity_Id gnat_entity, tree gnu_expr, bool definition)
align = MINIMUM_ATOMIC_ALIGNMENT;
#endif
/* Make a new type with the desired size and alignment, if needed.
But do not take into account alignment promotions to compute the
size of the object. */
/* Do not take into account aliased adjustments or alignment promotions
to compute the size of the object. */
tree gnu_object_size = gnu_size ? gnu_size : TYPE_SIZE (gnu_type);
/* If the object is aliased, of a constrained nominal subtype and its
size might be zero at run time, we force at least the unit size. */
if (Is_Aliased (gnat_entity)
&& !Is_Constr_Subt_For_UN_Aliased (gnat_type)
&& Is_Array_Type (Underlying_Type (gnat_type))
&& !TREE_CONSTANT (gnu_object_size))
gnu_size = size_binop (MAX_EXPR, gnu_object_size, bitsize_unit_node);
/* Make a new type with the desired size and alignment, if needed. */
if (gnu_size || align > 0)
{
tree orig_type = gnu_type;

4
gcc/testsuite/ChangeLog
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@ -1,3 +1,7 @@
2020-05-08 Eric Botcazou <ebotcazou@adacore.com>
* gnat.dg/addr15.adb: New test.
2020-05-08 Richard Biener <rguenther@suse.de>
* gnat.dg/opt83.adb: New testcase.

19
gcc/testsuite/gnat.dg/addr15.adb Normal file
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@ -0,0 +1,19 @@
-- { dg-do run }
with System; use System;
procedure Addr15 is
function Get_Bound (Param : Integer) return Integer is (Param);
type Alpha_Typ is array (1 .. Get_Bound (1)) of Integer;
type Beta_Typ is array (1 .. Get_Bound (0)) of Integer;
Alpha : Alpha_Typ;
Beta : aliased Beta_Typ;
begin
if Alpha'Address = Beta'Address then
raise Program_Error;
end if;
end;