-- ??? We want to migrate all platforms to use the same convention. As a
-- first step, we force this constant to always be True. This constant will
-- eventually be deleted after we have verified that the migration does not
- -- cause any unforseen adverse impact. We chose "__" because it is
+ -- cause any unforeseen adverse impact. We chose "__" because it is
-- supported on all platforms, which is not the case of "$".
procedure Get_External_Name
function Debug_Renaming_Declaration (N : Node_Id) return Node_Id;
-- The argument N is a renaming declaration. The result is a variable
-- declaration as described in the above paragraphs. If N is not a special
- -- debug declaration, then Empty is returned.
+ -- debug declaration, then Empty is returned. This function also takes care
+ -- of setting Materialize_Entity on the renamed entity where required.
---------------------------
-- Packed Array Encoding --
-- where discrim is the unqualified name of the variant. This field name is
-- built by gigi (not by code in this unit). For Unchecked_Union record,
- -- this discriminant will not appear in the record, and the debugger must
- -- proceed accordingly (basically it can treat this case as it would a C
- -- union).
+ -- this discriminant will not appear in the record (see Unchecked Unions,
+ -- below).
-- The type corresponding to this field has a name that is obtained by
-- concatenating the type name with the above string and is similar to a C
-- The name of the union member is encoded to indicate the choices, and
-- is a string given by the following grammar:
- -- union_name ::= {choice} | others_choice
+ -- member_name ::= {choice} | others_choice
-- choice ::= simple_choice | range_choice
-- simple_choice ::= S number
-- range_choice ::= R number T number
-- V1 : Var;
- -- In this case, the type var is represented as a struct with three fields,
- -- the first two are "disc" and "m", representing the values of these
- -- record components.
-
- -- The third field is a union of two types, with field names S1 and O. S1
- -- is a struct with fields "r" and "s", and O is a struct with fields "t".
+ -- In this case, the type var is represented as a struct with three fields.
+ -- The first two are "disc" and "m", representing the values of these
+ -- record components. The third field is a union of two types, with field
+ -- names S1 and O. S1 is a struct with fields "r" and "s", and O is a
+ -- struct with field "t".
+
+ ----------------------
+ -- Unchecked Unions --
+ ----------------------
+
+ -- The encoding for variant records changes somewhat under the influence
+ -- of a "pragma Unchecked_Union" clause:
+
+ -- 1. The discriminant will not be present in the record, although its
+ -- name is still used in the encodings.
+ -- 2. Variants containing a single component named "x" of type "T" may
+ -- be encoded, as in ordinary C unions, as a single field of the
+ -- enclosing union type named "x" of type "T", dispensing with the
+ -- enclosing struct. In this case, of course, the discriminant values
+ -- corresponding to the variant are unavailable. As for normal
+ -- variants, the field name "x" may be suffixed with ___XVL if it
+ -- has dynamic size.
+
+ -- For example, the type Var in the preceding section, if followed by
+ -- "pragma Unchecked_Union (Var);" may be encoded as a struct with two
+ -- fields. The first is "m". The second field is a union of two types,
+ -- with field names S1 and "t". As before, S1 is a struct with fields
+ -- "r" and "s". "t" is a field of type Integer.
------------------------------------------------
-- Subprograms for Handling Variant Encodings --
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