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| <a name="Working-with-declarations"></a> |
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| Next: <a href="Internal-structure.html#Internal-structure" accesskey="n" rel="next">Internal structure</a>, Up: <a href="Declarations.html#Declarations" accesskey="u" rel="up">Declarations</a> [<a href="index.html#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="Option-Index.html#Option-Index" title="Index" rel="index">Index</a>]</p> |
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| <a name="Working-with-declarations-1"></a> |
| <h4 class="subsection">10.4.1 Working with declarations</h4> |
| |
| <p>Some macros can be used with any kind of declaration. These include: |
| </p><dl compact="compact"> |
| <dt><code>DECL_NAME</code> |
| <a name="index-DECL_005fNAME"></a> |
| </dt> |
| <dd><p>This macro returns an <code>IDENTIFIER_NODE</code> giving the name of the |
| entity. |
| </p> |
| </dd> |
| <dt><code>TREE_TYPE</code> |
| <a name="index-TREE_005fTYPE-2"></a> |
| </dt> |
| <dd><p>This macro returns the type of the entity declared. |
| </p> |
| </dd> |
| <dt><code>EXPR_FILENAME</code> |
| <a name="index-EXPR_005fFILENAME"></a> |
| </dt> |
| <dd><p>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>. |
| </p> |
| </dd> |
| <dt><code>EXPR_LINENO</code> |
| <a name="index-EXPR_005fLINENO"></a> |
| </dt> |
| <dd><p>This macro returns the line number at which the entity was declared, as |
| an <code>int</code>. |
| </p> |
| </dd> |
| <dt><code>DECL_ARTIFICIAL</code> |
| <a name="index-DECL_005fARTIFICIAL"></a> |
| </dt> |
| <dd><p>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: |
| </p><div class="smallexample"> |
| <pre class="smallexample">struct S {}; |
| </pre></div> |
| <p>is roughly equivalent to C code like: |
| </p><div class="smallexample"> |
| <pre class="smallexample">struct S {}; |
| typedef struct S S; |
| </pre></div> |
| <p>The implicitly generated <code>typedef</code> declaration is represented by a |
| <code>TYPE_DECL</code> for which <code>DECL_ARTIFICIAL</code> holds. |
| </p> |
| </dd> |
| </dl> |
| |
| <p>The various kinds of declarations include: |
| </p><dl compact="compact"> |
| <dt><code>LABEL_DECL</code></dt> |
| <dd><p>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. |
| </p> |
| </dd> |
| <dt><code>CONST_DECL</code></dt> |
| <dd><p>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>. |
| </p> |
| </dd> |
| <dt><code>RESULT_DECL</code></dt> |
| <dd><p>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>. |
| </p> |
| </dd> |
| <dt><code>TYPE_DECL</code></dt> |
| <dd><p>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. |
| </p> |
| </dd> |
| <dt><code>VAR_DECL</code></dt> |
| <dd><p>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> |
| <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> |
| <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. |
| </p> |
| </dd> |
| <dt><code>PARM_DECL</code></dt> |
| <dd><p>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> |
| <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>. |
| </p> |
| </dd> |
| <dt><code>DEBUG_EXPR_DECL</code></dt> |
| <dd><p>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. |
| </p> |
| </dd> |
| <dt><code>FIELD_DECL</code></dt> |
| <dd><p>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> |
| <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. |
| </p> |
| </dd> |
| <dt><code>NAMESPACE_DECL</code></dt> |
| <dd><p>Namespaces provide a name hierarchy for other declarations. They |
| appear in the <code>DECL_CONTEXT</code> of other <code>_DECL</code> nodes. |
| </p> |
| </dd> |
| </dl> |
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