Rewrite the existing variant part code

This rewrites the existing variant part code to follow the new model
implemented in the previous patch.  The old variant part code is
removed.

This only affects Rust for the moment.  I tested this using various
version of the Rust compiler, including one that emits old-style enum
debuginfo, exercising the quirks code.

gdb/ChangeLog
2020-04-24  Tom Tromey  <tromey@adacore.com>

	* dwarf2/read.c (struct variant_field): Rewrite.
	(struct variant_part_builder): New.
	(struct nextfield): Remove "variant" field.  Add "offset".
	(struct field_info): Add "current_variant_part" and
	"variant_parts".
	(alloc_discriminant_info): Remove.
	(alloc_rust_variant): New function.
	(quirk_rust_enum): Update.
	(dwarf2_add_field): Set "offset" member.  Don't handle
	DW_TAG_variant_part.
	(offset_map_type): New typedef.
	(convert_variant_range, create_one_variant)
	(create_one_variant_part, create_variant_parts)
	(add_variant_property): New functions.
	(dwarf2_attach_fields_to_type): Call add_variant_property.
	(read_structure_type): Don't handle DW_TAG_variant_part.
	(handle_variant_part, handle_variant): New functions.
	(handle_struct_member_die): Use them.
	(process_structure_scope): Don't handle variant parts.
	* gdbtypes.h (TYPE_FLAG_DISCRIMINATED_UNION): Remove.
	(struct discriminant_info): Remove.
	(enum dynamic_prop_node_kind) <DYN_PROP_DISCRIMINATED>: Remove.
	(struct main_type) <flag_discriminated_union>: Remove.
	* rust-lang.c (rust_enum_p, rust_empty_enum_p): Rewrite.
	(rust_enum_variant): Return int.  Remove "contents".  Rewrite.
	(rust_print_enum, rust_print_struct_def, rust_evaluate_subexp):
	Update.
	* valops.c (value_union_variant): Remove.
	* value.h (value_union_variant): Don't declare.

1 files changed, 0 insertions, 8 deletions

diff --git a/gdb/value.h b/gdb/value.h
index dfe3e8e..ae859ca 100644
--- a/gdb/value.h
+++ b/gdb/value.h
@@ -1226,14 +1226,6 @@ extern struct type *result_type_of_xmethod (struct value *method,
 extern struct value *call_xmethod (struct value *method,
 				   gdb::array_view<value *> argv);
 
-/* Given a discriminated union type and some corresponding value
-   contents, this will return the field index of the currently active
-   variant.  This will throw an exception if no active variant can be
-   found.  */
-
-extern int value_union_variant (struct type *union_type,
-				const gdb_byte *contents);
-
 /* Destroy the values currently allocated.  This is called when GDB is
    exiting (e.g., on quit_force).  */
 extern void finalize_values ();