https://gcc.gnu.org/g:9903cea0ddfe3f9f5bcaa1e6812d24a250e17c17
commit r16-2007-g9903cea0ddfe3f9f5bcaa1e6812d24a250e17c17
Author: Steve Baird <ba...@adacore.com>
Date: Tue Jun 17 16:24:50 2025 -0700
ada: Missing component clause warning for discriminant of Unchecked_Union
type
Even when -gnatw.c is enabled, no warning about a missing component clause
should be generated if the placement of a discriminant of an Unchecked_Union
type is left unspecified in a record representation clause (such a
discriminant
occupies no storage). In determining whether to generate such a warning, in
some cases the compiler would incorrectly ignore an Unchecked_Union pragma
occurring after the record representation clause. This could result in a
spurious warning.
gcc/ada/ChangeLog:
* sem_ch13.adb (Analyze_Record_Representation_Clause): In deciding
whether to generate a warning about a missing component clause, in
addition to calling Is_Unchecked_Union also call a new local
function, Unchecked_Union_Pragma_Pending, which checks for the
case of a not-yet-analyzed Unchecked_Union pragma occurring later
in the declaration list.
Diff:
---
gcc/ada/sem_ch13.adb | 43 +++++++++++++++++++++++++++++++++++++++++--
1 file changed, 41 insertions(+), 2 deletions(-)
diff --git a/gcc/ada/sem_ch13.adb b/gcc/ada/sem_ch13.adb
index 09372a43e52c..99acbf89e4eb 100644
--- a/gcc/ada/sem_ch13.adb
+++ b/gcc/ada/sem_ch13.adb
@@ -8862,6 +8862,43 @@ package body Sem_Ch13 is
Num_Repped_Components : Nat := 0;
Num_Unrepped_Components : Nat := 0;
+ function Unchecked_Union_Pragma_Pending return Boolean;
+ -- Return True in the corner case of an Unchecked_Union pragma
+ -- occuring after the record representation clause (which
+ -- means that Is_Unchecked_Union will return False for Rectype,
+ -- even though it would return True if called later after the
+ -- pragma is analyzed).
+
+ ------------------------------------
+ -- Unchecked_Union_Pragma_Pending --
+ ------------------------------------
+
+ function Unchecked_Union_Pragma_Pending return Boolean is
+ Decl_List_Element : Node_Id := N;
+ Pragma_Arg : Node_Id;
+ begin
+ while Present (Decl_List_Element) loop
+ if Nkind (Decl_List_Element) = N_Pragma
+ and then Get_Pragma_Id (Decl_List_Element) =
+ Pragma_Unchecked_Union
+ and then not Is_Empty_List (Pragma_Argument_Associations
+ (Decl_List_Element))
+ then
+ Pragma_Arg := Get_Pragma_Arg
+ (First (Pragma_Argument_Associations
+ (Decl_List_Element)));
+ if Nkind (Pragma_Arg) = N_Identifier
+ and then Chars (Pragma_Arg) = Chars (Rectype)
+ then
+ return True;
+ end if;
+ end if;
+
+ Next (Decl_List_Element);
+ end loop;
+ return False;
+ end Unchecked_Union_Pragma_Pending;
+
begin
-- First count number of repped and unrepped components
@@ -8900,8 +8937,10 @@ package body Sem_Ch13 is
-- Ignore discriminant in unchecked union, since it is
-- not there, and cannot have a component clause.
- and then (not Is_Unchecked_Union (Rectype)
- or else Ekind (Comp) /= E_Discriminant)
+ and then (Ekind (Comp) /= E_Discriminant
+ or else not (Is_Unchecked_Union (Rectype)
+ or else
+ Unchecked_Union_Pragma_Pending))
then
Error_Msg_Sloc := Sloc (Comp);
Error_Msg_NE
