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<h4 class="subsection">10.4.1 Working with declarations</h4>
<p>Some macros can be used with any kind of declaration. These include:
<dl>
<dt><code>DECL_NAME</code><a name="index-DECL_005fNAME-1812"></a><dd>This macro returns an <code>IDENTIFIER_NODE</code> giving the name of the
entity.
<br><dt><code>TREE_TYPE</code><a name="index-TREE_005fTYPE-1813"></a><dd>This macro returns the type of the entity declared.
<br><dt><code>EXPR_FILENAME</code><a name="index-EXPR_005fFILENAME-1814"></a><dd>This macro returns the name of the file in which the entity was
declared, as a <code>char*</code>. For an entity declared implicitly by the
compiler (like <code>__builtin_memcpy</code>), this will be the string
<code>"<internal>"</code>.
<br><dt><code>EXPR_LINENO</code><a name="index-EXPR_005fLINENO-1815"></a><dd>This macro returns the line number at which the entity was declared, as
an <code>int</code>.
<br><dt><code>DECL_ARTIFICIAL</code><a name="index-DECL_005fARTIFICIAL-1816"></a><dd>This predicate holds if the declaration was implicitly generated by the
compiler. For example, this predicate will hold of an implicitly
declared member function, or of the <code>TYPE_DECL</code> implicitly
generated for a class type. Recall that in C++ code like:
<pre class="smallexample"> struct S {};
</pre>
<p class="noindent">is roughly equivalent to C code like:
<pre class="smallexample"> struct S {};
typedef struct S S;
</pre>
<p>The implicitly generated <code>typedef</code> declaration is represented by a
<code>TYPE_DECL</code> for which <code>DECL_ARTIFICIAL</code> holds.
</dl>
<p>The various kinds of declarations include:
<dl>
<dt><code>LABEL_DECL</code><dd>These nodes are used to represent labels in function bodies. For more
information, see <a href="Functions.html#Functions">Functions</a>. These nodes only appear in block
scopes.
<br><dt><code>CONST_DECL</code><dd>These nodes are used to represent enumeration constants. The value of
the constant is given by <code>DECL_INITIAL</code> which will be an
<code>INTEGER_CST</code> with the same type as the <code>TREE_TYPE</code> of the
<code>CONST_DECL</code>, i.e., an <code>ENUMERAL_TYPE</code>.
<br><dt><code>RESULT_DECL</code><dd>These nodes represent the value returned by a function. When a value is
assigned to a <code>RESULT_DECL</code>, that indicates that the value should
be returned, via bitwise copy, by the function. You can use
<code>DECL_SIZE</code> and <code>DECL_ALIGN</code> on a <code>RESULT_DECL</code>, just as
with a <code>VAR_DECL</code>.
<br><dt><code>TYPE_DECL</code><dd>These nodes represent <code>typedef</code> declarations. The <code>TREE_TYPE</code>
is the type declared to have the name given by <code>DECL_NAME</code>. In
some cases, there is no associated name.
<br><dt><code>VAR_DECL</code><dd>These nodes represent variables with namespace or block scope, as well
as static data members. The <code>DECL_SIZE</code> and <code>DECL_ALIGN</code> are
analogous to <code>TYPE_SIZE</code> and <code>TYPE_ALIGN</code>. For a declaration,
you should always use the <code>DECL_SIZE</code> and <code>DECL_ALIGN</code> rather
than the <code>TYPE_SIZE</code> and <code>TYPE_ALIGN</code> given by the
<code>TREE_TYPE</code>, since special attributes may have been applied to the
variable to give it a particular size and alignment. You may use the
predicates <code>DECL_THIS_STATIC</code> or <code>DECL_THIS_EXTERN</code> to test
whether the storage class specifiers <code>static</code> or <code>extern</code> were
used to declare a variable.
<p>If this variable is initialized (but does not require a constructor),
the <code>DECL_INITIAL</code> will be an expression for the initializer. The
initializer should be evaluated, and a bitwise copy into the variable
performed. If the <code>DECL_INITIAL</code> is the <code>error_mark_node</code>,
there is an initializer, but it is given by an explicit statement later
in the code; no bitwise copy is required.
<p>GCC provides an extension that allows either automatic variables, or
global variables, to be placed in particular registers. This extension
is being used for a particular <code>VAR_DECL</code> if <code>DECL_REGISTER</code>
holds for the <code>VAR_DECL</code>, and if <code>DECL_ASSEMBLER_NAME</code> is not
equal to <code>DECL_NAME</code>. In that case, <code>DECL_ASSEMBLER_NAME</code> is
the name of the register into which the variable will be placed.
<br><dt><code>PARM_DECL</code><dd>Used to represent a parameter to a function. Treat these nodes
similarly to <code>VAR_DECL</code> nodes. These nodes only appear in the
<code>DECL_ARGUMENTS</code> for a <code>FUNCTION_DECL</code>.
<p>The <code>DECL_ARG_TYPE</code> for a <code>PARM_DECL</code> is the type that will
actually be used when a value is passed to this function. It may be a
wider type than the <code>TREE_TYPE</code> of the parameter; for example, the
ordinary type might be <code>short</code> while the <code>DECL_ARG_TYPE</code> is
<code>int</code>.
<br><dt><code>DEBUG_EXPR_DECL</code><dd>Used to represent an anonymous debug-information temporary created to
hold an expression as it is optimized away, so that its value can be
referenced in debug bind statements.
<br><dt><code>FIELD_DECL</code><dd>These nodes represent non-static data members. The <code>DECL_SIZE</code> and
<code>DECL_ALIGN</code> behave as for <code>VAR_DECL</code> nodes.
The position of the field within the parent record is specified by a
combination of three attributes. <code>DECL_FIELD_OFFSET</code> is the position,
counting in bytes, of the <code>DECL_OFFSET_ALIGN</code>-bit sized word containing
the bit of the field closest to the beginning of the structure.
<code>DECL_FIELD_BIT_OFFSET</code> is the bit offset of the first bit of the field
within this word; this may be nonzero even for fields that are not bit-fields,
since <code>DECL_OFFSET_ALIGN</code> may be greater than the natural alignment
of the field's type.
<p>If <code>DECL_C_BIT_FIELD</code> holds, this field is a bit-field. In a bit-field,
<code>DECL_BIT_FIELD_TYPE</code> also contains the type that was originally
specified for it, while DECL_TYPE may be a modified type with lesser precision,
according to the size of the bit field.
<br><dt><code>NAMESPACE_DECL</code><dd>Namespaces provide a name hierarchy for other declarations. They
appear in the <code>DECL_CONTEXT</code> of other <code>_DECL</code> nodes.
</dl>
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