#### 23.3.3.7 Types In Guile

GDB represents types from the inferior in objects of type `<gdb:type>`.

The following type-related procedures are provided by the `(gdb)` module.

Scheme Procedure: type? object

  Return `#t` if object is an object of type `<gdb:type>`. Otherwise return `#f`.

Scheme Procedure: lookup-type name [#:block block]

  This function looks up a type by its name, which must be a string.

  If block is given, it is an object of type `<gdb:block>`, and name is looked up in that scope. Otherwise, it is searched for globally.

  Ordinarily, this function will return an instance of `<gdb:type>`. If the named type cannot be found, it will throw an exception.

Scheme Procedure: type-code type

  Return the type code of type. The type code will be one of the `TYPE_CODE_` constants defined below.

Scheme Procedure: type-tag type

  Return the tag name of type. The tag name is the name after `struct`, `union`, or `enum` in C and C`++`; not all languages have this concept. If this type has no tag name, then `#f` is returned.

Scheme Procedure: type-name type

  Return the name of type. If this type has no name, then `#f` is returned.

Scheme Procedure: type-print-name type

  Return the print name of type. This returns something even for anonymous types. For example, for an anonymous C struct `"struct {...}"` is returned.

Scheme Procedure: type-sizeof type

  Return the size of this type, in target `char` units. Usually, a target’s `char` type will be an 8-bit byte. However, on some unusual platforms, this type may have a different size.

Scheme Procedure: type-strip-typedefs type

  Return a new `<gdb:type>` that represents the real type of type, after removing all layers of typedefs.

Scheme Procedure: type-array type n1 [n2]

  Return a new `<gdb:type>` object which represents an array of this type. If one argument is given, it is the inclusive upper bound of the array; in this case the lower bound is zero. If two arguments are given, the first argument is the lower bound of the array, and the second argument is the upper bound of the array. An array’s length must not be negative, but the bounds can be.

Scheme Procedure: type-vector type n1 [n2]

  Return a new `<gdb:type>` object which represents a vector of this type. If one argument is given, it is the inclusive upper bound of the vector; in this case the lower bound is zero. If two arguments are given, the first argument is the lower bound of the vector, and the second argument is the upper bound of the vector. A vector’s length must not be negative, but the bounds can be.

  The difference between an `array` and a `vector` is that arrays behave like in C: when used in expressions they decay to a pointer to the first element whereas vectors are treated as first class values.

Scheme Procedure: type-pointer type

  Return a new `<gdb:type>` object which represents a pointer to type.

Scheme Procedure: type-range type

  Return a list of two elements: the low bound and high bound of type. If type does not have a range, an exception is thrown.

Scheme Procedure: type-reference type

  Return a new `<gdb:type>` object which represents a reference to type.

Scheme Procedure: type-target type

  Return a new `<gdb:type>` object which represents the target type of type.

  For a pointer type, the target type is the type of the pointed-to object. For an array type (meaning C-like arrays), the target type is the type of the elements of the array. For a function or method type, the target type is the type of the return value. For a complex type, the target type is the type of the elements. For a typedef, the target type is the aliased type.

  If the type does not have a target, this method will throw an exception.

Scheme Procedure: type-const type

  Return a new `<gdb:type>` object which represents a `const`-qualified variant of type.

Scheme Procedure: type-volatile type

  Return a new `<gdb:type>` object which represents a `volatile`-qualified variant of type.

Scheme Procedure: type-unqualified type

  Return a new `<gdb:type>` object which represents an unqualified variant of type. That is, the result is neither `const` nor `volatile`.

Scheme Procedure: type-num-fields

  Return the number of fields of `<gdb:type>` type.

Scheme Procedure: type-fields type

  Return the fields of type as a list. For structure and union types, `fields` has the usual meaning. Range types have two fields, the minimum and maximum values. Enum types have one field per enum constant. Function and method types have one field per parameter. The base types of C`++` classes are also represented as fields. If the type has no fields, or does not fit into one of these categories, an empty list will be returned. See Fields of a type in Guile.

Scheme Procedure: make-field-iterator type

  Return the fields of type as a <gdb:iterator> object. See Iterators In Guile.

Scheme Procedure: type-field type field-name

  Return field named field-name in type. The result is an object of type `<gdb:field>`. See Fields of a type in Guile. If the type does not have fields, or field-name is not a field of type, an exception is thrown.

  For example, if `some-type` is a `<gdb:type>` instance holding a structure type, you can access its `foo` field with:

      (define bar (type-field some-type "foo"))

  `bar` will be a `<gdb:field>` object.

Scheme Procedure: type-has-field? type name

  Return `#t` if `<gdb:type>` type has field named name. Otherwise return `#f`.

Each type has a code, which indicates what category this type falls into. The available type categories are represented by constants defined in the `(gdb)` module:

`TYPE_CODE_PTR`

  The type is a pointer.

`TYPE_CODE_ARRAY`

  The type is an array.

`TYPE_CODE_STRUCT`

  The type is a structure.

`TYPE_CODE_UNION`

  The type is a union.

`TYPE_CODE_ENUM`

  The type is an enum.

`TYPE_CODE_FLAGS`

  A bit flags type, used for things such as status registers.

`TYPE_CODE_FUNC`

  The type is a function.

`TYPE_CODE_INT`

  The type is an integer type.

`TYPE_CODE_FLT`

  A floating point type.

`TYPE_CODE_VOID`

  The special type `void`.

`TYPE_CODE_SET`

  A Pascal set type.

`TYPE_CODE_RANGE`

  A range type, that is, an integer type with bounds.

`TYPE_CODE_STRING`

  A string type. Note that this is only used for certain languages with language-defined string types; C strings are not represented this way.

`TYPE_CODE_BITSTRING`

  A string of bits. It is deprecated.

`TYPE_CODE_ERROR`

  An unknown or erroneous type.

`TYPE_CODE_METHOD`

  A method type, as found in C`++`.

`TYPE_CODE_METHODPTR`

  A pointer-to-member-function.

`TYPE_CODE_MEMBERPTR`

  A pointer-to-member.

`TYPE_CODE_REF`

  A reference type.

`TYPE_CODE_CHAR`

  A character type.

`TYPE_CODE_BOOL`

  A boolean type.

`TYPE_CODE_COMPLEX`

  A complex float type.

`TYPE_CODE_TYPEDEF`

  A typedef to some other type.

`TYPE_CODE_NAMESPACE`

  A C`++` namespace.

`TYPE_CODE_DECFLOAT`

  A decimal floating point type.

`TYPE_CODE_INTERNAL_FUNCTION`

  A function internal to GDB. This is the type used to represent convenience functions (see Convenience Funs).

Further support for types is provided in the `(gdb types)` Guile module (see Guile Types Module).

Each field is represented as an object of type `<gdb:field>`.

The following field-related procedures are provided by the `(gdb)` module:

Scheme Procedure: field? object

  Return `#t` if object is an object of type `<gdb:field>`. Otherwise return `#f`.

Scheme Procedure: field-name field

  Return the name of the field, or `#f` for anonymous fields.

Scheme Procedure: field-type field

  Return the type of the field. This is usually an instance of `<gdb:type>`, but it can be `#f` in some situations.

Scheme Procedure: field-enumval field

  Return the enum value represented by `<gdb:field>` field.

Scheme Procedure: field-bitpos field

  Return the bit position of `<gdb:field>` field. This attribute is not available for `static` fields (as in C`++`).

Scheme Procedure: field-bitsize field

  If the field is packed, or is a bitfield, return the size of `<gdb:field>` field in bits. Otherwise, zero is returned; in which case the field’s size is given by its type.

Scheme Procedure: field-artificial? field

  Return `#t` if the field is artificial, usually meaning that it was provided by the compiler and not the user. Otherwise return `#f`.

Scheme Procedure: field-base-class? field

  Return `#t` if the field represents a base class of a C`++` structure. Otherwise return `#f`.