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Initial support for variant parts

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This adds some initial support for variant parts to gdbtypes.h.  A
variant part is represented as a union.  The union has a flag
indicating that it has a discriminant, and information about the
discriminant is attached using the dynamic property system.

2018-02-26  Tom Tromey  <tom@tromey.com>

	* value.h (value_union_variant): Declare.
	* valops.c (value_union_variant): New function.
	* gdbtypes.h (TYPE_FLAG_DISCRIMINATED_UNION): New macro.
	(struct discriminant_info): New.
	(enum dynamic_prop_node_kind) <DYN_PROP_DISCRIMINATED>: New
	enumerator.
	(struct main_type) <flag_discriminated_union>: New field.
This commit is contained in:
Tom Tromey
2018-02-09 13:31:42 -07:00
parent 15ce8941e7
commit 7c22600aab
4 changed files with 113 additions and 0 deletions
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51
gdb/gdbtypes.h
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@ -312,6 +312,14 @@ DEF_ENUM_FLAGS_TYPE (enum type_instance_flag_value, type_instance_flags);
#define TYPE_FLAG_ENUM(t) (TYPE_MAIN_TYPE (t)->flag_flag_enum)
/* * True if this type is a discriminated union type. Only valid for
TYPE_CODE_UNION. A discriminated union stores a reference to the
discriminant field along with the discriminator values in a dynamic
property. */
#define TYPE_FLAG_DISCRIMINATED_UNION(t) \
(TYPE_MAIN_TYPE (t)->flag_discriminated_union)
/* * Constant type. If this is set, the corresponding type has a
const modifier. */
@ -381,6 +389,39 @@ DEF_ENUM_FLAGS_TYPE (enum type_instance_flag_value, type_instance_flags);
#define TYPE_ADDRESS_CLASS_ALL(t) (TYPE_INSTANCE_FLAGS(t) \
& TYPE_INSTANCE_FLAG_ADDRESS_CLASS_ALL)
/* * Information needed for a discriminated union. A discriminated
union is handled somewhat differently from an ordinary union.
One field is designated as the discriminant. Only one other field
is active at a time; which one depends on the value of the
discriminant and the data in this structure.
Additionally, it is possible to have a univariant discriminated
union. In this case, the union has just a single field, which is
assumed to be the only active variant -- in this case no
discriminant is provided. */
struct discriminant_info
{
/* * The index of the discriminant field. If -1, then this union
must have just a single field. */
int discriminant_index;
/* * The index of the default branch of the union. If -1, then
there is no default branch. */
int default_index;
/* * The discriminant values corresponding to each branch. This has
a number of entries equal to the number of fields in this union.
If discriminant_index is not -1, then that entry in this array is
not used. If default_index is not -1, then that entry in this
array is not used. */
ULONGEST discriminants[1];
};
enum dynamic_prop_kind
{
PROP_UNDEFINED, /* Not defined. */
@ -439,6 +480,9 @@ enum dynamic_prop_node_kind
/* A property providing an array's byte stride. */
DYN_PROP_BYTE_STRIDE,
/* A property holding information about a discriminated union. */
DYN_PROP_DISCRIMINATED,
};
/* * List for dynamic type attributes. */
@ -658,6 +702,13 @@ struct main_type
unsigned int flag_flag_enum : 1;
/* * True if this type is a discriminated union type. Only valid
for TYPE_CODE_UNION. A discriminated union stores a reference to
the discriminant field along with the discriminator values in a
dynamic property. */
unsigned int flag_discriminated_union : 1;
/* * A discriminant telling us which field of the type_specific
union is being used for this type, if any. */