c-tree.texi

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continues until a non-array type is found, and the qualification of this
type is examined.)  So, for example, @code{CP_TYPE_CONST_P} will hold of
the type @code{const int ()[7]}, denoting an array of seven @code{int}s.

The following functions and macros deal with cv-qualification of types:
@ftable @code
@item CP_TYPE_QUALS
This macro returns the set of type qualifiers applied to this type.
This value is @code{TYPE_UNQUALIFIED} if no qualifiers have been
applied.  The @code{TYPE_QUAL_CONST} bit is set if the type is
@code{const}-qualified.  The @code{TYPE_QUAL_VOLATILE} bit is set if the
type is @code{volatile}-qualified.  The @code{TYPE_QUAL_RESTRICT} bit is
set if the type is @code{restrict}-qualified.

@item CP_TYPE_CONST_P
This macro holds if the type is @code{const}-qualified.

@item CP_TYPE_VOLATILE_P
This macro holds if the type is @code{volatile}-qualified.

@item CP_TYPE_RESTRICT_P
This macro holds if the type is @code{restrict}-qualified.

@item CP_TYPE_CONST_NON_VOLATILE_P
This predicate holds for a type that is @code{const}-qualified, but
@emph{not} @code{volatile}-qualified; other cv-qualifiers are ignored as
well: only the @code{const}-ness is tested.

@item TYPE_MAIN_VARIANT
This macro returns the unqualified version of a type.  It may be applied
to an unqualified type, but it is not always the identity function in
that case.
@end ftable

A few other macros and functions are usable with all types:
@ftable @code
@item TYPE_SIZE
The number of bits required to represent the type, represented as an
@code{INTEGER_CST}.  For an incomplete type, @code{TYPE_SIZE} will be
@code{NULL_TREE}.

@item TYPE_ALIGN
The alignment of the type, in bits, represented as an @code{int}.

@item TYPE_NAME
This macro returns a declaration (in the form of a @code{TYPE_DECL}) for
the type.  (Note this macro does @emph{not} return a
@code{IDENTIFIER_NODE}, as you might expect, given its name!)  You can
look at the @code{DECL_NAME} of the @code{TYPE_DECL} to obtain the
actual name of the type.  The @code{TYPE_NAME} will be @code{NULL_TREE}
for a type that is not a built-in type, the result of a typedef, or a
named class type.

@item CP_INTEGRAL_TYPE
This predicate holds if the type is an integral type.  Notice that in
C++, enumerations are @emph{not} integral types.

@item ARITHMETIC_TYPE_P
This predicate holds if the type is an integral type (in the C++ sense)
or a floating point type.

@item CLASS_TYPE_P
This predicate holds for a class-type.

@item TYPE_BUILT_IN
This predicate holds for a built-in type.

@item TYPE_PTRMEM_P
This predicate holds if the type is a pointer to data member.

@item TYPE_PTR_P
This predicate holds if the type is a pointer type, and the pointee is
not a data member.

@item TYPE_PTRFN_P
This predicate holds for a pointer to function type.

@item TYPE_PTROB_P
This predicate holds for a pointer to object type.  Note however that it
does not hold for the generic pointer to object type @code{void *}.  You
may use @code{TYPE_PTROBV_P} to test for a pointer to object type as
well as @code{void *}.

@item TYPE_CANONICAL
This macro returns the ``canonical'' type for the given type
node. Canonical types are used to improve performance in the C++ and
Objective-C++ front ends by allowing efficient comparison between two
type nodes in @code{same_type_p}: if the @code{TYPE_CANONICAL} values
of the types are equal, the types are equivalent; otherwise, the types
are not equivalent. The notion of equivalence for canonical types is
the same as the notion of type equivalence in the language itself. For
instance,

When @code{TYPE_CANONICAL} is @code{NULL_TREE}, there is no canonical
type for the given type node. In this case, comparison between this
type and any other type requires the compiler to perform a deep,
``structural'' comparison to see if the two type nodes have the same
form and properties.

The canonical type for a node is always the most fundamental type in
the equivalence class of types. For instance, @code{int} is its own
canonical type. A typedef @code{I} of @code{int} will have @code{int}
as its canonical type. Similarly, @code{I*}@ and a typedef @code{IP}@
(defined to @code{I*}) will has @code{int*} as their canonical
type. When building a new type node, be sure to set
@code{TYPE_CANONICAL} to the appropriate canonical type. If the new
type is a compound type (built from other types), and any of those
other types require structural equality, use
@code{SET_TYPE_STRUCTURAL_EQUALITY} to ensure that the new type also
requires structural equality. Finally, if for some reason you cannot
guarantee that @code{TYPE_CANONICAL} will point to the canonical type,
use @code{SET_TYPE_STRUCTURAL_EQUALITY} to make sure that the new
type--and any type constructed based on it--requires structural
equality. If you suspect that the canonical type system is
miscomparing types, pass @code{--param verify-canonical-types=1} to
the compiler or configure with @code{--enable-checking} to force the
compiler to verify its canonical-type comparisons against the
structural comparisons; the compiler will then print any warnings if
the canonical types miscompare.

@item TYPE_STRUCTURAL_EQUALITY_P
This predicate holds when the node requires structural equality
checks, e.g., when @code{TYPE_CANONICAL} is @code{NULL_TREE}.

@item SET_TYPE_STRUCTURAL_EQUALITY
This macro states that the type node it is given requires structural
equality checks, e.g., it sets @code{TYPE_CANONICAL} to
@code{NULL_TREE}.

@item same_type_p
This predicate takes two types as input, and holds if they are the same
type.  For example, if one type is a @code{typedef} for the other, or
both are @code{typedef}s for the same type.  This predicate also holds if
the two trees given as input are simply copies of one another; i.e.,
there is no difference between them at the source level, but, for
whatever reason, a duplicate has been made in the representation.  You
should never use @code{==} (pointer equality) to compare types; always
use @code{same_type_p} instead.
@end ftable

Detailed below are the various kinds of types, and the macros that can
be used to access them.  Although other kinds of types are used
elsewhere in G++, the types described here are the only ones that you
will encounter while examining the intermediate representation.

@table @code
@item VOID_TYPE
Used to represent the @code{void} type.

@item INTEGER_TYPE
Used to represent the various integral types, including @code{char},
@code{short}, @code{int}, @code{long}, and @code{long long}.  This code
is not used for enumeration types, nor for the @code{bool} type.
The @code{TYPE_PRECISION} is the number of bits used in
the representation, represented as an @code{unsigned int}.  (Note that
in the general case this is not the same value as @code{TYPE_SIZE};
suppose that there were a 24-bit integer type, but that alignment
requirements for the ABI required 32-bit alignment.  Then,
@code{TYPE_SIZE} would be an @code{INTEGER_CST} for 32, while
@code{TYPE_PRECISION} would be 24.)  The integer type is unsigned if
@code{TYPE_UNSIGNED} holds; otherwise, it is signed.

The @code{TYPE_MIN_VALUE} is an @code{INTEGER_CST} for the smallest
integer that may be represented by this type.  Similarly, the
@code{TYPE_MAX_VALUE} is an @code{INTEGER_CST} for the largest integer
that may be represented by this type.

@item REAL_TYPE
Used to represent the @code{float}, @code{double}, and @code{long
double} types.  The number of bits in the floating-point representation
is given by @code{TYPE_PRECISION}, as in the @code{INTEGER_TYPE} case.

@item FIXED_POINT_TYPE
Used to represent the @code{short _Fract}, @code{_Fract}, @code{long
_Fract}, @code{long long _Fract}, @code{short _Accum}, @code{_Accum},
@code{long _Accum}, and @code{long long _Accum} types.  The number of bits
in the fixed-point representation is given by @code{TYPE_PRECISION},
as in the @code{INTEGER_TYPE} case.  There may be padding bits, fractional
bits and integral bits.  The number of fractional bits is given by
@code{TYPE_FBIT}, and the number of integral bits is given by @code{TYPE_IBIT}.
The fixed-point type is unsigned if @code{TYPE_UNSIGNED} holds; otherwise,
it is signed.
The fixed-point type is saturating if @code{TYPE_SATURATING} holds; otherwise,
it is not saturating.

@item COMPLEX_TYPE
Used to represent GCC built-in @code{__complex__} data types.  The
@code{TREE_TYPE} is the type of the real and imaginary parts.

@item ENUMERAL_TYPE
Used to represent an enumeration type.  The @code{TYPE_PRECISION} gives
(as an @code{int}), the number of bits used to represent the type.  If
there are no negative enumeration constants, @code{TYPE_UNSIGNED} will
hold.  The minimum and maximum enumeration constants may be obtained
with @code{TYPE_MIN_VALUE} and @code{TYPE_MAX_VALUE}, respectively; each
of these macros returns an @code{INTEGER_CST}.

The actual enumeration constants themselves may be obtained by looking
at the @code{TYPE_VALUES}.  This macro will return a @code{TREE_LIST},
containing the constants.  The @code{TREE_PURPOSE} of each node will be
an @code{IDENTIFIER_NODE} giving the name of the constant; the
@code{TREE_VALUE} will be an @code{INTEGER_CST} giving the value
assigned to that constant.  These constants will appear in the order in
which they were declared.  The @code{TREE_TYPE} of each of these
constants will be the type of enumeration type itself.

@item BOOLEAN_TYPE
Used to represent the @code{bool} type.

@item POINTER_TYPE
Used to represent pointer types, and pointer to data member types.  The
@code{TREE_TYPE} gives the type to which this type points.  If the type
is a pointer to data member type, then @code{TYPE_PTRMEM_P} will hold.
For a pointer to data member type of the form @samp{T X::*},
@code{TYPE_PTRMEM_CLASS_TYPE} will be the type @code{X}, while
@code{TYPE_PTRMEM_POINTED_TO_TYPE} will be the type @code{T}.

@item REFERENCE_TYPE
Used to represent reference types.  The @code{TREE_TYPE} gives the type
to which this type refers.

@item FUNCTION_TYPE
Used to represent the type of non-member functions and of static member
functions.  The @code{TREE_TYPE} gives the return type of the function.
The @code{TYPE_ARG_TYPES} are a @code{TREE_LIST} of the argument types.
The @code{TREE_VALUE} of each node in this list is the type of the
corresponding argument; the @code{TREE_PURPOSE} is an expression for the
default argument value, if any.  If the last node in the list is
@code{void_list_node} (a @code{TREE_LIST} node whose @code{TREE_VALUE}
is the @code{void_type_node}), then functions of this type do not take
variable arguments.  Otherwise, they do take a variable number of
arguments.

Note that in C (but not in C++) a function declared like @code{void f()}
is an unprototyped function taking a variable number of arguments; the
@code{TYPE_ARG_TYPES} of such a function will be @code{NULL}.

@item METHOD_TYPE
Used to represent the type of a non-static member function.  Like a
@code{FUNCTION_TYPE}, the return type is given by the @code{TREE_TYPE}.
The type of @code{*this}, i.e., the class of which functions of this
type are a member, is given by the @code{TYPE_METHOD_BASETYPE}.  The
@code{TYPE_ARG_TYPES} is the parameter list, as for a
@code{FUNCTION_TYPE}, and includes the @code{this} argument.

@item ARRAY_TYPE
Used to represent array types.  The @code{TREE_TYPE} gives the type of
the elements in the array.  If the array-bound is present in the type,
the @code{TYPE_DOMAIN} is an @code{INTEGER_TYPE} whose
@code{TYPE_MIN_VALUE} and @code{TYPE_MAX_VALUE} will be the lower and
upper bounds of the array, respectively.  The @code{TYPE_MIN_VALUE} will
always be an @code{INTEGER_CST} for zero, while the
@code{TYPE_MAX_VALUE} will be one less than the number of elements in
the array, i.e., the highest value which may be used to index an element
in the array.

@item RECORD_TYPE
Used to represent @code{struct} and @code{class} types, as well as
pointers to member functions and similar constructs in other languages.
@code{TYPE_FIELDS} contains the items contained in this type, each of
which can be a @code{FIELD_DECL}, @code{VAR_DECL}, @code{CONST_DECL}, or
@code{TYPE_DECL}.  You may not make any assumptions about the ordering
of the fields in the type or whether one or more of them overlap.  If
@code{TYPE_PTRMEMFUNC_P} holds, then this type is a pointer-to-member
type.  In that case, the @code{TYPE_PTRMEMFUNC_FN_TYPE} is a
@code{POINTER_TYPE} pointing to a @code{METHOD_TYPE}.  The
@code{METHOD_TYPE} is the type of a function pointed to by the
pointer-to-member function.  If @code{TYPE_PTRMEMFUNC_P} does not hold,
this type is a class type.  For more information, see @pxref{Classes}.

@item UNION_TYPE
Used to represent @code{union} types.  Similar to @code{RECORD_TYPE}
except that all @code{FIELD_DECL} nodes in @code{TYPE_FIELD} start at
bit position zero.

@item QUAL_UNION_TYPE
Used to represent part of a variant record in Ada.  Similar to
@code{UNION_TYPE} except that each @code{FIELD_DECL} has a
@code{DECL_QUALIFIER} field, which contains a boolean expression that
indicates whether the field is present in the object.  The type will only
have one field, so each field's @code{DECL_QUALIFIER} is only evaluated
if none of the expressions in the previous fields in @code{TYPE_FIELDS}
are nonzero.  Normally these expressions will reference a field in the
outer object using a @code{PLACEHOLDER_EXPR}.

@item UNKNOWN_TYPE
This node is used to represent a type the knowledge of which is
insufficient for a sound processing.

@item OFFSET_TYPE
This node is used to represent a pointer-to-data member.  For a data
member @code{X::m} the @code{TYPE_OFFSET_BASETYPE} is @code{X} and the
@code{TREE_TYPE} is the type of @code{m}.

@item TYPENAME_TYPE
Used to represent a construct of the form @code{typename T::A}.  The
@code{TYPE_CONTEXT} is @code{T}; the @code{TYPE_NAME} is an
@code{IDENTIFIER_NODE} for @code{A}.  If the type is specified via a
template-id, then @code{TYPENAME_TYPE_FULLNAME} yields a
@code{TEMPLATE_ID_EXPR}.  The @code{TREE_TYPE} is non-@code{NULL} if the
node is implicitly generated in support for the implicit typename
extension; in which case the @code{TREE_TYPE} is a type node for the
base-class.

@item TYPEOF_TYPE
Used to represent the @code{__typeof__} extension.  The
@code{TYPE_FIELDS} is the expression the type of which is being
represented.
@end table

There are variables whose values represent some of the basic types.
These include:
@table @code
@item void_type_node
A node for @code{void}.

@item integer_type_node
A node for @code{int}.

@item unsigned_type_node.
A node for @code{unsigned int}.

@item char_type_node.
A node for @code{char}.
@end table
@noindent
It may sometimes be useful to compare one of these variables with a type
in hand, using @code{same_type_p}.