https://gcc.gnu.org/g:ff89e55497f1a36b6a37a43c5837d89d30fe9601
commit r16-1335-gff89e55497f1a36b6a37a43c5837d89d30fe9601
Author: Gary Dismukes <dismu...@adacore.com>
Date: Sat Mar 8 01:05:35 2025 +0000
ada: Missing discriminant check on assignment of Bounded_Vector aggregate
When a container aggregate for a Bounded_Vector type involves an iterated
association that is assigned to a vector object whose capacity (as defined
by the Capacity discriminant) is less than the number of elements of the
aggregate, Constraint_Error should be raised due to failing a discriminant
check on the assignment. But the compiler fails to do proper expansion,
plus omits the check, and instead creates a temporary whose capacity is
bounded by that of the target vector of the assignment. It attempts to
assign all elements of the aggregate to the temporary, resulting in
a failure on a call to the Replace_Element operation that assigns past
the length of the temporary vector (which can result in a Storage_Error
due to a segment violation).
This is fixed by ensuring that the temporary object is declared with
an unconstrained base subtype rather than the assignment target's
constrained subtype.
gcc/ada/ChangeLog:
* exp_aggr.adb (Expand_Container_Aggregate): Use the Base_Type of
the
subtype provided by the context as the subtype of the temporary
object
initialized by the aggregate.
Diff:
---
gcc/ada/exp_aggr.adb | 11 ++++++++++-
1 file changed, 10 insertions(+), 1 deletion(-)
diff --git a/gcc/ada/exp_aggr.adb b/gcc/ada/exp_aggr.adb
index 5450402f4749..8db15fa6a11d 100644
--- a/gcc/ada/exp_aggr.adb
+++ b/gcc/ada/exp_aggr.adb
@@ -7503,10 +7503,19 @@ package body Exp_Aggr is
Set_Assignment_OK (Lhs);
Aggr_Code := Build_Container_Aggr_Code (N, Typ, Lhs, Init);
+
+ -- Use the unconstrained base subtype of the subtype provided by
+ -- the context for declaring the temporary object (which may come
+ -- from a constrained assignment target), to ensure that the
+ -- aggregate can be successfully expanded and assigned to the
+ -- temporary without exceeding its capacity. (Later assignment
+ -- of the temporary to a target object may result in failing
+ -- a discriminant check.)
+
Prepend_To (Aggr_Code,
Make_Object_Declaration (Loc,
Defining_Identifier => Obj_Id,
- Object_Definition => New_Occurrence_Of (Typ, Loc),
+ Object_Definition => New_Occurrence_Of (Base_Type (Typ), Loc),
Expression => Init));
Insert_Actions (N, Aggr_Code);
